Contribution to the development of a process for color improvement of low grade dark maple syrup by

adsorption on activated carbon

Mémoire

Bita Sadeghi-Tabatabai

Maîtrise en génie agroalimentaire

Maître ès sciences (M.Sc.)

Québec, Canada

© Bita Sadeghi-Tabatabai, 2015

iii

Résumé

Dans ce travail, nous avons utilisé le charbon actif (trois types) pour décolorer le sirop

d'érable foncé, classé dans la catégorie ``Non retenu`` de la classification du Québec du

sirop d’érable. Nous avons testé l'efficacité de la rétention des pigments colorés du sirop

d'érable sur le charbon actif en grains et en poudre. Aussi, nous avons comparé les

différentes efficacités de ces matériaux. La première étape de nos essais expérimentaux a eu

pour but de suivre les cinétiques d'adsorption des pigments. Dans cette partie, plusieurs

paramètres expérimentaux ont été optimisés par utilisation d'un plan factoriel complet; à

savoir : le temps d'agitation (20,40, 60 min), la masse du charbon actif utilisée par 100 ml

de sirop (0.1, 0.3, 0.5 g), le type du charbon actif (I, II, III), le diamètre moyen des

particules du charbon (25, 50, 75 µm), la vitesse d'agitation (200, 400, 600 rpm) et la

température (40,60, 80 °C). La variable dépendante que nous avons considérée dans ce

projet est la transmittance de la lumière du sirop mesurée à 560 nm. La deuxième étape a

été consacrée sur l'étude du pouvoir adsorbant des trois types de charbons actifs utilisés

avec l’application des modèles de Langmuir, Freundlich et de Langmuir-Freundlich pour

décrire les cinétiques d’adsorption. Les résultats obtenus ont montré que la décoloration du

sirop d’érable foncé est optimale avec les paramètres suivants : temps d'agitation t = 40

min, masse du charbon actif ajouté m = 0.3 g et charbon actif de type III. Ces paramètres

ont donné une valeur de la transmittance de la lumière à 560 nm de 83.7 ± 0.2 %; et qui

classe le sirop dans la catégorie Extra claire. Ensuite, ce travail a montré que seul le

charbon actif de type III vérifiait à la fois une cinétique d’adsorption qui se décrit par les

isothermes de sorption de Langmuir, Freundlich et Langmuir-Freundlich. Finalement, un

autre plan d'expérience avait complété dans ce travail et qui portait sur l'optimisation de la

taille des particules du charbon et qui a montré qu’une granulométrie moyenne d = 25 µm

(mésopores) était la plus optimale pour décolore le sirop d’érable avec une agitation de 200

rpm à une température T = 80°C.

v

Abstract

Low grade dark maple syrup was successfully discolored on activated carbon. Several

experimental parameters were tested, namely the mixing time (20, 40, 60 min),

concentration of the activated carbon (0.1, 0.3, 0.5 g/100 mL), type of activated carbon (I,

II, III), particle size (25, 50, 75 μm), stirring speed (200, 400, 600 rpm), and temperature

(40, 60, 80°C). The obtained results showed that the discoloration is optimal by applying

the parameters such as an agitation time of 40 min with an activated carbon of type III at a

concentration of 0.3 g/100 mL. These parameters yielded a light transmittance of 83.70 ±

0.21%, which ranks the syrup in the extra clear class. The results showed that among the

tested carbons, the adsorption on the type carbon of III followed the Langmuir, Freundlich

and Langmuir-Freundlich isotherms. Regarding the effect of the particle size, the obtained

results showed that a mean size of 25 µm with a stirring speed of 200 rpm and a working

temperature of 80°C was the most effective. The optimized conditions showed a good

adequacy with the Langmuir and Freundlich models. The discoloration process by using the

activated carbon of type III followed pseudo-second order kinetics.

vii

Table of contents

Résumé ............................................................................................................................................................... iii

Abstract ............................................................................................................................................................... v

Table of contents ................................................................................................................................................ vii

List of tables ....................................................................................................................................................... ix

List of figures ...................................................................................................................................................... xi

Dédicaces ......................................................................................................................................................... xiii

Remerciements ................................................................................................................................................. xv

Avant-propos .................................................................................................................................................... xvii

INTRODUCTION ................................................................................................................................................. 1

CHAPTER 1: LITRATURE REVIEW ................................................................................................................... 3

1.1. Maple syrup ............................................................................................................................................. 3

1.1.1. Brief history of maple syrup and its production ..................................................................................... 3

1.1.2. Composition of the maple syrup ........................................................................................................... 3

1.1.3. Economic importance of the maple syrup ............................................................................................. 4

1.1.4. Classification of the maple syrup .......................................................................................................... 4

1.1.5. Causes of the color darkening .............................................................................................................. 7

1.1.5.1. Microorganism activity ....................................................................................................................... 7

1.1.5.2. Boiling ................................................................................................................................................ 7

1.1.5.2.1. Millard reaction (browning non-enzymatic reaction) ................................................................... 7

1.1.5.2.2. Reaction of caramelization ....................................................................................................... 13

1.1.5.3. Type of storage containers .............................................................................................................. 14

1.1.6. Possible ways for commercial use of dark maple syrup ..................................................................... 14

1.2. Activated carbon .................................................................................................................................... 15

1.2.1. Activated carbon ................................................................................................................................. 15

1.2.2. The application of activated carbon .................................................................................................... 17

1.2.2.1. Air treatment .................................................................................................................................... 17

1.2.2.2. Hydrogen sulfide (H2S) and odor control ......................................................................................... 17

1.2.2.3. Gaseous waste incinerators and biogas purification ........................................................................ 17

1.2.2.4. Wastewater treatment ...................................................................................................................... 18

1.2.2.5. Food industry and pharmaceutical applications ............................................................................... 18

CHAPTER 2: HYPOTHESIS AND OBJECTIVES ............................................................................................. 21

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2.1. Research Hypothesis ................................................................................................................................. 21

2.2. General objective ........................................................................................................................................ 21

2.2.1. Specific objectives ................................................................................................................................... 22

CHAPTER 3: MATERIALS, METHODS, RESULTS AND DISCUSSION .......................................................... 23

Abstract ............................................................................................................................................................. 26

Résumé ............................................................................................................................................................. 27

3.1. Introduction ................................................................................................................................................. 28

3.2. Materials and Methods ............................................................................................................................... 30

3.2.1. Reagents and Samples ....................................................................................................................... 30

3.2.2. Characterization of the activated carbon ............................................................................................. 30

3.2.2.1. Mean particle size ............................................................................................................................ 30

3.2.2.2. Scanning electron microscopy (SEM) and Energy dispersive X-ray spectrometer (EDS) ................ 30

3.2.2.3. Bulk density ...................................................................................................................................... 31

3.2.3. Experimental procedure ...................................................................................................................... 31

3.2.4. Statistical modeling and adsorption isotherms .................................................................................... 31

3.2.5. Experimental design and statistical analysis ....................................................................................... 32

3.3. Results and Discussion .......................................................................................................................... 33

3.3.1. Characteristics of the used activated carbons ..................................................................................... 33

3.3.2. Effect of the concentration and type of the added activated carbon .................................................... 34

3.3.3. Effect of the mixing stirring time .......................................................................................................... 36

3.3.4. Effect of the temperature, particle size and mixing speed ................................................................... 37

3.3.5. Statistical modeling of the discoloration process ................................................................................. 38

3.3.5.1. Adsorption isotherm models ............................................................................................................. 39

3.3.5.2. Dark maple syrup discoloration kinetic order ................................................................................... 41

Conclusion ......................................................................................................................................................... 42

Acknowledgements ........................................................................................................................................... 42

Conflict of Interest Statement ............................................................................................................................ 43

CONCLUSION GÉNÉRALE ET PERSPÉCTIVES ............................................................................................ 45

RÉFÉRENCES .................................................................................................................................................. 67

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List of tables

Table 1: Federal classification of maple syrup. ........................................................................................... 5

Table 2: Classification of the maple syrup according to the Quebec standard. ...................................... 6

Table 3: Color classification of the maple syrup (Québec office Standard, 2011). ................................ 6

Table 4: Adsorption isotherm models used to describe the color removal from dark maple syrup. .. 47

Table 5: Variation of transmittances at different stirring time and different mass of the activated

carbon (type III). ............................................................................................................................................ 48

Table 6: Pseudo-first and pseudo-second order equations used to describe the adsorption kinetic

models of maple syrup discoloration. ......................................................................................................... 49

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List of figures

Figure 1: Maillard reaction scheme adapted (Hodge, 1953)...................................................................... 9

Figure 2: Representation of the first stage of the Maillard reaction corresponding to the

condensation phase (Çelebi, 2006). ............................................................................................................. 10

Figure 3: Stage of the Amadori rearrangement of the Millard reaction (Hodge, 1953). ..................... 12

Figure 4: Strecker degradation occuring during the Maillard reaction (Yaylayan, 2003). .................. 13

Figure 5: Different materials used in activated carbon production. ........................................................ 15

Figure 6: Activated carbon in granular, crushed and powder form. ....................................................... 15

Figure 7: Schematic representation of the experimental set-up. ............................................................. 52

Figure 8: Activated carbon particle size distribution. ............................................................................... 53

Figure 9: Scanning electron micrographs of the surface activated carbon particles used in maple

syrup discoloration. ....................................................................................................................................... 54

Figure 10: Energy dispersive X-ray spectrometer of different type of activated carbon. .................... 55

Figure 11: Bulk density comparison of different activated carbon. ........................................................ 56

Figure 12: Transmittance as a function of time at different activated carbon concentrations and

different activated carbons: (a) Type I, (b) Type II, (c) Type III, (d) Type IV. .................................... 57

Figure 13: Transmittance as a function of activated carbon mass at different activated carbon and

different agitation time: (a) 20 min, (b) 40 min, (c) 60 min. ................................................................... 58

Figure 14: Transmittance as a function of activated carbon mass at different stirring time and

different activated carbon. (a) Type I, (b) Type II, (c) Type III, (d) Type IV. ...................................... 59

Figure 15: Transmittance as a function of particle diameters of activated carbon type III at different

working temperatures and different stirring speed: (a) 200 rpm, (b) 400 rpm, (c) 600 rpm. .............. 60

Figure 16: Transmittance as a function of stirring speed at different particle size of activated carbon

III and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C. .................................................. 61

Figure 17: Transmittance as a function of particle size of activated carbon III at different stirring

speed and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C.............................................. 62

Figure 18: Response surface at X1 = 0, X2 (-1, 0, +1), and X3 (-1, 0, +1). .......................................... 63

Figure 19: Iso-response curve at different level of X1 (-1, 0, +1), X2 (-1, 0, +1) and X3 (-1, 0, +1).

.......................................................................................................................................................................... 64

Figure 20: Coloration concentration of the maple syrup solution as a function of coloration

concentration adsorbed by activated carbon at different adsorption isotherm type. (a) type I, (b)

type II, and (c) type III. ................................................................................................................................. 65

Figure 21: Kinetic models of the adsorption by using activated carbon type III. (a) Pseudo-first

order; (b) Pseudo-second order. .................................................................................................................. 66

xiii

Dédicaces

À mes chers parents : merci à mes parents Sariyeh Alizadeh et Ahmad Sadeghi Tabatabai

pour leur amour inconditionnel et leur soutien.

Enfin, je dédicace ce mémoire à la communauté scientifique internationale et à l’Université

Laval qui m’a fourni tout le nécessaire pour réaliser ce travail et en garder de nombreux

bons souvenirs qui resteront avec moi à jamais.

xv

Remerciements

Tout d'abord, je remercie le professeur Mohammed Aïder qui m'a accueillie dans son

équipe de recherche. Qu'il trouve ici l'expression de ma profonde gratitude pour m'avoir fait

bénéficier de sa compétence et de ses connaissances scientifiques.

Mes sincères remerciements se portent vers Dr Amara Aït-Aissa pour ses conseils et sa

disponibilité. Je lui exprime toute ma gratitude pour l'intérêt constant qu'il a porté à mon

travail.

Je tiens à remercier sincèrement les membres du jury d'avoir accepté de participer à

corriger ce mémoire, mais aussi pour l'attention qu'ils ont témoignée à mon travail.

Mes remerciements les plus sincères vont aussi à madame Diane Gagnon et madame

Jocelyne Giasson. Je leur exprime toute ma gratitude pour leur aide concernant les analyses

avec le spectrophotomètre et les analyses de couleurs.

Je ne saurais oublier de remercier tous mes ami(e)s avec qui j'ai partagé le laboratoire et le

bureau. Merci à Ourdia, Alexey, Nata'lia, Mabrouk, Zeinabou.

Je profite de ce moment pour adresser ma gratitude et mes remerciements à toute ma

famille, surtout à mes très chers parents, Sariyeh et Ahmad qui ont toujours tout sacrifié

pour moi. Je remercie ma sœur Gita et mes frères Babak et Barmak pour leur

encouragement.

Merci à tous !

xvii

Avant-propos

Ce mémoire se compose de trois parties principales. Une introduction générale, une

revue de littérature qui porte sur deux éléments principaux; à savoir, la coloration du sirop

d’érable et la décoloration par du charbon actif et une partie ``Résultats et discussion`` sous

forme d'un article scientifique rédigé en anglais soumis pour publication dans Food

Bioscience, un journal international avec comité de lecture. Les participants à la rédaction

de l’article sont : Bita Sadeghi-Tabatabai, candidate à la maîtrise avec mémoire en génie

agroalimentaire, Dr Amara Aït Aissa, chercheur postdoctoral et Dr Mohammed Aider,

professeur et responsable du projet. L’article s’intitule ``Improvement of the color of low

grade dark maple syrup by adsorption on activated carbon and study of the adsorption

kinetics``.

1

INTRODUCTION

Ce projet se veut une contribution à la valorisation des sirops d'érable des catégories

non conforme (NC) et retenu (RE) via une décoloration par adsorption sur du charbon actif

en utilisant des conditions opératoires facilement reproductible par l’industrie du sirop

d’érable du Québec. Le but final étant de produire du sirop commercialisable de haute

qualité. Le présent projet a été entrepris suite à une réflexion sur la problématique entourant

l’absence de valorisation efficace du sirop d’érable foncé et le manque d’études

scientifiques, tant académiques qu’industrielles sur ce sujet. En effet, selon les statistiques

de la Fédération des producteurs acéricoles du Québec, en 2013, la production des sirops

d'érable des catégories non conforme (NC) et retenu (RE) était de 0.6 et 0.2 millions de

livres, respectivement. Elle était de 1.8 et 0.3 millions de livres en 2012. Comme ces sirops

ne sont pas commercialisables, ils s'accumulent d'année en année et occupent inutilement

des espaces importants dans les entrepôts. Par conséquent, il est important de trouver des

moyens efficaces et peu coûteux pour donner de la valeur à ces sirops. Cela permettra de

générer des revenus supplémentaires aux producteurs et de libérer des espaces

d'entreposage inutilement occupés. L'amélioration de la couleur et du goût des sirops des

catégories NC et RE permettra de leur trouver un marché dans l'industrie de la

transformation des aliments, mais surtout en exportation, car, la législation nationale par

rapport aux produits de l'érable ne s'applique pas de la même façon pour les produits

destinés à l’exportation. Comme la couleur du sirop sera nettement améliorée et comme ce

paramètre est d’une grande importance technologique, il est attendu à ce qu’il serait

possible et technologiquement faisable de fabriquer du sucre d'érable granulé de haute

qualité à partir des sirops obtenus suite à la décoloration des sirops de grade NC et RE.

Conséquemment, l'application de la technologie de cristallisation par refroidissement aux

sirops générés suite à la décoloration sur du charbon actif permettra de produire des

produits dérivés d’une apparence et attributs organoleptiques semblables à ceux faits à

partir de sirop d'érable des catégories A ou B.

L'objectif principal de ce projet de recherche est d'appliquer la technologie

d’adsorption sur du charbon actif de grade alimentaire pour une amélioration substantielle

de la couleur sirops d'érable des catégories non conforme (NC) et retenu (RE). Pour

2

atteindre l’objectif final, un dispositif expérimental de type factoriel sera utilisé pour

générer un maximum de données qui nous permettront de bien comprendre l’effet de

chaque paramètre expérimental sur la variable dépendante principale qui est la couleur

exprimée par la valeur de la transmittance de lumière mesurée à 560 nm. Le temps

d'agitation du mélange sirop avec du charbon, la masse du charbon actif utilisée par volume

de sirop, le type du charbon actif et sa granulométrie, ainsi que la vitesse d'agitation et la

température sont des variables indépendantes qui seront mises à l’étude dans le présent

projet.

3

CHAPTER 1: LITRATURE REVIEW

1.1. Maple syrup

1.1.1. Brief history of maple syrup and its production

Maple syrup production is attributed to indigenous inhabitants of North America

and is produced from the sap collected from the sugar maple tree Acer saccharum.

Evaporation of water to obtain concentrated maple sap was done by the natives inside clay

pots by placing hot stones in the bucket. Also, the sap was frozen overnight and a layer of

the formed ice was removed so as more concentrated sap was obtained. Iron and copper

kettles were introduced to the process by the first white settlers. The use of wooden

containers hung from the trees for the collection of sap had a good efficiency. In 1872, an

evaporator with two pan as well as a metal arch was developed for reducing boiling time of

the maple sap. During the 1970, tubing systems were equipped with vacuum pumps and the

sap was transferred from the tree to the evaporator. Later, reverse osmosis filters was used

to eliminate part of water of the sap before it was boiled. Today, processing technology of

maple sap has been improved for enhancing the rate and quality of production by using

stainless steel evaporators for boiling the maple sap, new tubing systems as well as new

filtering techniques such as more effective reverse osmosis (Wood et al., 2012). Maple

syrup is produced traditionally by boiling sap collected from various maple tree in the

sugarhouse by evaporating water and concentrating the sugar content up to 66–67° brix. It

has a special flavour and smell (Kallio et al., 1987). The syrup is produced during short

season consisting of four to eight weeks in late winter and early spring (Clément et al.,

2010; Filteau et al., 2012; Koffi et al., 2014; Yuan et al., 2013).

1.1.2. Composition of the maple syrup

Maple syrup is a sugary product and contains is mainly composed of sacccharose

with a content of 60-67%, reducing sugars (glucose, fructose, hexose) with content of 0.1-

10%, oligosaccharides and polysaccharides (0.1-4%), organic acids (0.6% of malic acid,

0.06% of succinic acid, 0.006% of formic acid) and traces of tartaric, citric, and oxalic

acids. It contains also flavouring compounds resulting from the Maillard reaction between

4

the amino acids and the reducing sugars, flavonoides and minerals such as potassium

(˷2000mg/kg), calcium (˷1000 mg/kg), magnesium (˷200 mg/kg), manganese (˷40mg/kg),

zinc (˷10 mg/kg) and sodium (˷10 mg/kg) (Khalf et al., 2010; Perkins and van den Berg,

2009). Maple syrup contains also some phytochemicals as phenolics, and more than fifty

phenolics and phenolic derivatives (Wild and Yanai, 2015).

1.1.3. Economic importance of the maple syrup

The industry of maple sap transformation plays very important role in the

economics of Canada and the Unites States which are the only maple syrup producing

countries in the world (Rapp and Crone, 2015). In 2006, Canada was the largest maple

syrup producer with 82% of that production with a production of 33,745 metric tonnes

(MT) valued at CAN $177,9 million, while the United States produced 7,24 MT of maple

syrup valued at US $ 45.3 million (AAC, 2007). In 2011, there were 10,000 maple farms

in Canada with over 44 million taps, approximately 4,000 taps per farm. Quebec is the

largest maple syrup producing province with 92.39% of domestic production, Ontario with

2.86% and New Brunswick with 0.32% in 2012 (Agriculture and Agri-Food Canada,

2014). From commercial point of view, maple syrup production plays an important

economic role. In fact, Canada with exports of $ 249 million is the largest exporter of

maple products (85%) in the world. Quebec has 94% of the Canadian maple product

exports to the countries such as United States, Japan and Germany (AAC, 2014).

1.1.4. Classification of the maple syrup Maple syrup is categorized based on its light transmission measured at a wavelength

of 560 nm as specified by the International Maple Syrup Institute (IMSI). It is classified

into four categories: light (>75 %), amber (50–75 %), dark (25–50 %), and very dark

(<25 %) (Perkins and van den Berg, 2009). From commercial point of view, the browning

in the syrup has a negative impact. Moreover, it is usually accompanied by some sensorial

defects. The maple season is between a late winter and early spring. The amber syrup

(light) is resulted from sap which runs of the early season. The syrup becomes darker in

color when the season warms up. The maple syrups are variable in color and vary from pale

golden to dark brown. Maple syrup is graded base on the color, clearness and flavor. It

must contain at least 65% solid (sugar) (ACIA, 2015). In Canada, the Canadian Food

5

Inspection Agency (CFIA) is the regulatory agency and responsible for the quality

requirements for maple syrup. The CFIA approves standards and regulatory framework for

food safety requirements for maple syrup which is classified based on its colour and flavour

(Clément et al., 2010; Perkins and van den Berg, 2009). There are two types of

classification for syrup maple in Canada: the federal and provincial classification. Federal

classification standard consists of three classes and five grades of syrup: Canada 1, (Extra

light, Light, Medium), Canada 2 (Amber), Canada 3 (Dark) and syrups from any other

category with flavour flaws (ACIA, 2015; Québec, 2015) (Table 1).

Table 1: Federal classification of maple syrup.

Canada No.1 Extra light

Light

Medium

Canada No.2

Amber

Canada.No.3 Dark, or any

other ungraded

category

The provincial classification of Québec consists of two categories and five colour classes:

AA (extra Light), A (Light), B (Medium), C (amber) and D (dark amber and strong taste

and is used for industrial purpose) (Québec Maple Syrup Producers Federation) (Tables 2

and 3). According to this a regulation, the color shall be determined optically by a

spectrophotometer or a visual glass comparator (Québec, 2015).

6

Table 2: Classification of the maple syrup according to the Quebec standard.

Category

No 1

Extra-light

Light

Medium

Amber

Category

No 2

Extra-light

Light

Medium

Amber

Dark

Table 3: Color classification of the maple syrup (Québec office Standard, 2011).

Item Color class Percentage of Light Transmission

1. Extra Light 75% or more

2. Light 60.5% or more, but less than 75%

3. Medium 44% or more, but less than 60.5%

4. Amber 27% or more, but less than 44%

5. Dark Less than 27%

In the Unites States of America (USA), maple syrup is categorized into two grade by color

and flavour. Grade A and Grade B under the authority of the U.S. Department of

Agriculture (Standards for Grades of Maple Syrup) (Houston, 1980).

Grade ``A``: This maple syrup has a bright color and have a moderate flavour than Grad B

that is of dark grade with rich flavour.

Grade A light amber: This type of maple syrup is lighter than the USDA light Amber Glass

Color standard in color.

Grade A medium amber: This maple syrup is darken than light amber but it is no darker

than the USDA light Amber Glass Color standard in color.

Grade A dark amber: This Grade of maple syrup is darker than medium amber, but is no

darker than the USDA Dark Amber Glass Color Standard in color.

7

Grade ``B``: It is characterized by a fairly good color and this kind of maple syrup is

darker than the USDA Dark Amber Glass Color Standard, but is not off-color for any

reason with a fairly good flavor.

1.1.5. Causes of the color darkening

1.1.5.1. Microorganism activity

In late winter, sap is clear with a weak sweet taste. The biochemistry occurred in

the sap results in different changes of color and flavor of the maple syrup produced. Maple

syrup of dark grades is generally produced from sap with high concentration of

microorganisms while a sap which is not affected by microorganism activity gives

possibility of making a lighter grades of syrup (Filteau et al., 2012). Color changes

occurring in the sap during boiling and those resulted from the microorganism activity in

the maple syrup is considered as the main cause of color darkening and caramelization

(Lagacé et al., 2006). Microorganisms in the maple syrup are a factor of the enzymatic

hydrolysis of sucrose-producing sugars (glucose and fructose) and those are responsible of

the intense caramel flavor and dark color (Sy, 1908). Microorganisms such as

Pseudomonas fluorescens and Guehomyces Pullulans were found in several production

sites in different regions of Quebec. Moreover, different yeasts (Candida) were related

with fructose and glucose concentrations in maple syrup (Filteau et al., 2011). P.

fluorescens group bacteria and some yeast were associated to vanilla attributes of maple

syrup when the maple syrup was produced at the end of the harvesting season (Filteau et

al., 2010, 2011, 2012).

1.1.5.2. Boiling

Dark color appears from a browning reaction when the sap is boiled further during

the evaporation process and putting too much sap in evaporation are the main factors of the

formation of a darker colored syrup during the stages of boiling of maple sap (Asadi, 2007).

1.1.5.2.1. Millard reaction (browning non-enzymatic reaction)

The most important change during processing of maple syrup is the browning

reaction known as non-enzymatic browning which is associated with the Millard reaction.

This reaction is complex and involves different the low molecular weight compounds

8

(Raisi and Aroujalian, 2007). This chemical reaction takes place between the reducing

sugars (glucose and fructose) (Ames, 2009) which are carbonyl compounds produced by

the decomposition of sucrose via bacterial activity in the maple sap and the amino acids

(amino groups of proteins) present in the sap at high temperatures (Carabasa-Giribet and

Ibarz-Ribas, 2000). The formation of Brown-colored (Melanoidins) is the consequence of

polymerisation reactions of highly reactive intermediates formed within the Maillard

reaction (Ekasari et al., 1986). Three major steps of the Maillard reaction are observed: a

condensation reaction, Amadori rearrangement and polymerisation or formation of the

brown color (high molecular weight melanoidins) (Figure 1) (Frazier, 2004). However,

most of formed colorant agents can be removed by purification (Eskin, 1990; Manley,

2000).

9

Figure 1: Maillard reaction scheme adapted (Hodge, 1953).

First stage (Condensation): Glucose syrups with high DE could have good reaction with

proteins (amino acids) (Dziedzic and Kearsley, 1984). A condensation product (N-

substituted glycosylamine) is derived from a reaction between a reducing sugar (glucose

and fructose) with an amino acid or protein of sap. N-substituted glycosilamine is obtained

as a result of a nucleophilic attack (NH2) of an amino acid on the electrophilic carbonyl

group of the sugar (Çelebi, 2006). Aldosylamine (when the reducing sugar is an aldose) or

ketosylamine (when the reducing sugar is a ketose) are formed rapidly as Schiff base after

loss of water (Figure 2).

10

Figure 2: Representation of the first stage of the Maillard reaction corresponding to the

condensation phase (Çelebi, 2006).

Second stage (Amadori rearrangement or Heyns): The Amadori rearrangement is the

second step in the Maillard reaction corresponding to the phase of glycosylamines

formation by the Amadori arrangement (Bristow and S. Isaacs, 1999). It leads to the

formation of heterocyclics by the Amadori rearrangement that are responsible for the

flavor and odor of the maple syrup. Aldosylamines and ketosylamines could have various

transformation. Aldosylamines lead to ketosamines and ketosylamines lead to aldosamines

by Heyns rearrangement. These reactions are catalysed by carboxyl function of the amino

acids. Thereafter, aldosamines and ketosamines obtained from the Amadori rearrangement

have various decomposition pathways involving cleavage and dehydration reaction. Thus,

the creation of small molecules, aromatic substances or the carbonyl compounds (such as

reductones) and polycarbonyles is very unstable. The reductones are dicetonics substances

11

(R-CO-CO-R) are extremely reactive. The Strecker degradation is autocatalytic and it

involves destruction of α-amino acids and formation of aromatic molecules like aldehydes.

Morselli and Whalen (1986) reported that, in the end of season, there is a trend to

diversification of amino acids in the sap with an increasing concentrations. This

degradation is characterized by a production of CO2. At pH = 7 or blow, furfural is formed

from an enolization of the Amadori product. At the pH of sap (syrup) above 7,

hydroxyethyl furfural (HMF) is formed HMF (Çelebi, 2006) (Figures 3, 4).

Third stage (polymerization and browning): The third stage is the polymerization of

various substances formed during the previous step. Moreover, some low molecular weight

molecules, volatile compounds and odorants are also formed together with the brown or

black pigments. These pigments called melanoidines and they are complex molecules with

high molecular weight. Temperature, the reaction time, water content, concentration and

the nature of the precursors influence this stage of the Mailllard reaction (Hodge, 1953).

12

Figure 3: Stage of the Amadori rearrangement of the Millard reaction (Hodge, 1953).

13

Figure 4: Strecker degradation occuring during the Maillard reaction (Yaylayan, 2003).

1.1.5.2.2. Reaction of caramelization

This brown color is produced from heating of sucrose (sugar) solution in the

evaporator during boiling by the breakdown of sucrose to glucose and fructose (Asadi,

2006). This thermal degradation doesn't involve presence of amino acids and proteins.

Three main product are of dehydration are formed: Caramelan (C12H18O9) and two

polymers which are caramelen (C36H50O25) and caramelin (C125H188O80). An intense heat

equal or higher than 200 C leads to the pyrolyse (degradation) and this degradation

involves break of the osidic links and intermolecular rearrangement (Ramırez-Jiménez et

al., 2000). A smell of burn of the syrup is the quality change caused when containers are

filled with very hot syrup and these containers are closely stacked together. Intensive heat

coupled to a high cooling time enhances the formation of this sensory defect. Burn in the

syrup causes the change of the syrup grade from Amber grade to the Dark (Purlis, 2010).

Thus, to avoid darkening, hot syrup inside of containers should be cooled previously the

containers are packed together. Moreover, the containers must be separated to facilitate air

circulation and the cooling of the syrup.

14

1.1.5.3. Type of storage containers

The type of storage containers can affect the color of the maple syrup during

storage. It has been reported that plastic containers are the main factor influencing the color

darkening after three months in storage (Morselli, 1980). The syrup packed in tinned steel

containers produces light grade of the maple syrup due to increased leached tin and

develops a flavour of high iron after the tin coating dissolves. Glass container was also

reported to be responsible for the darkening of maple syrup but not such as plastic

containers (ACIA, 2015).

1.1.6. Possible ways for commercial use of dark maple syrup

As it has been highlighted above, the use of dark maple syrup is quite limited

because of the non-attractive color, strong smell and presence of odor of caramelization.

All these compounds are formed as a result of different chemical reactions such as

condensation, polymerization and transformation. To make such syrup usable for food

applications, these compounds must be removed. Theoretically, different processes can be

applied to achieve this objective. For example, the odor can be improved following

deodorization under vacuum and the color can be improved by adsorption. The first

objective is quite difficult to be attained. Indeed, the evaporation will not remove the

strong smell because the responsible molecules are difficult to evaporate. Moreover, it is

technologically a huge process.

One of the promising ways to enhance the use of such syrup by lightening its color

and diminishing the intensity of the smell consists of a treatment on active surface that can

absorb the pigments giving the dark color and strong smell of burn (caramelization).

Moreover, such technology must be easy to use in the real conditions of maple syrup

industry. Adsorption on food grade active carbon offers the possibility of achieving this

objective while making the process feasible from technological point of view.

15

1.2. Activated carbon

1.2.1. Activated carbon

Activated carbon is manufactured from carbon containing materials such as wood,

charcoal, peat, bituminous coal, coconut shells, lignite, pecan shells, bones, pulp mill black,

ash saw dust, plastic residuals by activation processes (Worch, 1991). It find several

applications in different fields and processes, including the food industry. To obtain

activated carbon, different steps are required. The first one consist of carbonization which

is necessary to transform the raw material into carbonized carbon which is the first step to

make activated carbon (Bandosz and Kante, 2015). The carbon from carbonaceous

materials is a material that has an infinity pore (a few Angstroms) clogged with organic

matter (Figure 5). To be converted into activated carbon, the carbonaceous material must

be free of all organic material. For this, the high-temperature used for heating in a rotary or

vertical oven is 700 ° C and more (Strachowski and Bystrzejewski, 2015).

Figure 5: Different materials used in activated carbon production.

Figure 6: Activated carbon in granular, crushed and powder form.

16

The second step consists of activation and there are two activation methods: (a) the

physical process gas in which the coal is mixed with water vapor and nitrogen (Angın et al.,

2013). Organic matter is destroyed and then a carbon skeleton that has it special properties

is obtained. The whole is heated at 700-1000 ° C according to the equation:

2 2C + H O CO + H

(b) the chemical process in which the carbonaceous material is mixed with sulfuric acid,

phosphoric acid or zinc chloride and the whole is heated to 400-800 °C. This type of

activation is used for the activated carbon in powder or granular forms (Figure 6) (Angın et

al., 2013).

The large surface area of activated carbon provides a high adsorptive capacity to

this material. It is this great adsorptive capacity which is the basis for numerous industrial

as well as medical uses (Gao et al.; Sun and Webley, 2010). There are different kinds of

activated carbon adsorption with different characteristics. The adsorptive characteristics are

determined by the configuration of the surface area of activated carbon. Moreover,

activated carbon is widely used in the treatment of acute poisoning with substances such as

acetaminophen, salicylates, barbiturates and tricyclic antidepressants. The activated carbon

absorbs strongly aromatic substances such as the foregoing, reducing their absorption from

the gastrointestinal tract. At the other hand, most inorganic poisons are not significantly

absorbed by the charcoal. Industrially, the activated carbon is produced in three main types:

carbon grain, powder and extruded. These three categories of activated carbon can have

properties tailored depending on the type of application (Danish et al., 2014).

Activated carbon has a specific surface area between 800 to 1500 m2/g and that is

why all ions of activated carbon are available for the absorption process (Asadi, 2007).

Activated carbon mainly contains micropores with diameters smaller than 2 nm. Thus, high

microporous structure and a high degree of surface reactivity make activated carbons

suitable for different adsorption process. This specific surface area is used for decolorizing

and removing impurities from fluids (Kumar, 2003).

17

1.2.2. The application of activated carbon

1.2.2.1. Air treatment

It is used for volatile organic compounds (VOCs) removal from the air. Indeed,

activated carbon is the leading technology in cutting VOCs in the air or any other gas. It is

used in particular cases for the elimination of siloxanes biogas. In many cases, a compound

may be removed below the detection level. Therefore, the more stringent rules on air

quality and safety can be met. The technology is reliable, robust and has proven effective

over the years (Baléo and Subrenat, 2000; Bañuelos et al., 2014; Guo et al., 2014).

1.2.2.2. Hydrogen sulfide (H2S) and odor control

The greater environmental awareness and improving the working conditions have

focused the concentration on the reduction of odors from sewage treatment plants,

municipal and industrial effluents. Harmful compounds such as H2S and mercaptans are

readily captured by the adsorption and removed by chemisorption or by catalytic

conversion, while others organic contaminants are readily adsorbed by the coal (Masuda et

al., 1999; Sitthikhankaew et al., 2011; Xiao et al., 2008a, b).

1.2.2.3. Gaseous waste incinerators and biogas purification

The incineration of household waste, hazardous industrial waste, medical waste,

sewage sludge and crematoria lead to the formation of a flue gas containing a wide range of

pollutants. Dioxins and heavy metals such as mercury and cadmium are not normally

removed at sufficiently low concentrations by conventional treatment. The use of powdered

activated carbon is an effective method to reduce concentrations of these substances below

the levels specified by legislation. For biogas, it is produced by anaerobic digestion of

organic matter. It is used locally for the production of green energy. Activated carbon is

needed in biogas plants to remove impurities and to protect cogeneration engines from

corrosion or damage from silica deposits. It is also essential when it comes to bring purity

biomethane at a level sufficient to allow its injection into the network of use (Esteves et al.,

2008; Hernández et al., 2011a; Hernández et al., 2011b; Pipatmanomai et al., 2009).

18

1.2.2.4. Wastewater treatment

Activated carbon is one of the most effective ways to eliminate a wide range of

contaminants and it is highly effective for wastewater treatment generated from different

industries. It is also used for the treatment of landfill leachate or contaminated soils. As

strong adsorbent, it is capable of processing a large number of contaminants from such

water. Activated carbon can be used to treat all or a portion of the contaminants directly or

in combination with other steps. At the moment when the environmental protection is a

necessity, recycling of process water in the industrial setting is a new economic path.

Indeed, this type of treatment will reduce the impact on the environment, reduce disposal

costs of waste water and reduce raw water samples of the natural environment. Here are

some of the water contaminants that activated carbon is able to remove: non-biodegradable

organics, absorbable organic halogenated, organic halogens, toxic molecules and coloring

pigments (Altmann et al., 2014; Guo et al., 2014; Hadi et al., 2015b; Mailler et al.; Margot

et al., 2013; Ruhl et al., 2014; Tammaro et al., 2014).

1.2.2.5. Food industry and pharmaceutical applications

In the food industry, the granular activated carbon is used for different applications

such as for the:

Discoloration of cane and beet sugar syrups as well as purification of the glucose,

fructose and sweeteners (Mudoga et al., 2008; Pendyal et al., 1999b).

Discoloration and purification of organic acids and amino acids from fermentation

processes (Ayranci and Duman, 2006; Bayram and Ayranci, 2012).

Removal of chlorine in the industries using this chemical for the production of beer,

soft drinks and other food products (Marsh and Rodríguez-Reinoso, 2006;

Razvigorova et al., 1998).

Purification of the carbon dioxide used in soft drinks (Holden, 1998).

Decaffeination of tea and coffee (Clarke, 2003; Dong et al., 2011; Marsh and

Rodríguez-Reinoso, 2006; Przepiórski, 2006; Vuong et al., 2013).

Removal of unwanted natural compounds and harmful anthropogenic compounds

from edible oils such as polycyclic aromatic hydrocarbons (Hadi et al., 2015a;

Sardella et al., 2015; Updyke et al., 2012).

19

Elimination of undesirable odoriferous compounds and dyes from glycerin.

Removal of off-tastes, odor or undesirable compounds dyes from alcoholic

beverages such as wine, vodka, vermouth, beer (Rodriguez-Illera et al.; Siebert,

2013; Vanderhaegen et al., 2006).

Purification of fruit juices by eliminating undesirable dyes or compounds such as

mycotoxins patulin in apple juice (Angin, 2014; Diban et al., 2007;

Laksameethanasana et al., 2012; Soto et al., 2011; Suárez-Quiroz et al., 2014).

Debittering of intermediate food or flavorings (Saha and Hayashi, 2001).

Get value-added molecules of agricultural products (AlOthman et al., 2014;

Galiatsatou et al., 2002; Pendyal et al., 1999a; Sardella et al., 2015).

In the pharmaceutical industry, activated carbons are used in many industrial process for

the discoloration, purification, catalysis and cleanup (Kyzas and Deliyanni). Moreover,

activated carbon is a gastrointestinal adsorbent. The large surface area of activated carbon

provides a high absorbent capacity to this material. It is effective in adsorbing aromatic or

benzenoid-like substances, fatty acids and fatty alcohols. Aromatics, such as

acetaminophen, salicylates, barbiturates and tricyclic antidepressants, are strongly absorbed

by the charcoal (Baccar et al., 2012; Calisto et al., 2015; Margot et al., 2013; Mestre et al.,

2014; Snyder et al., 2007; Wang et al.).

Considering the aforementioned information about the adsorptive capacity of the

activated carbon in different applications, it seems possible to apply this material to adsorb

coloring pigments and other molecules responsible of the strong smell in the dark maple

syrup.

21

CHAPTER 2: HYPOTHESIS AND OBJECTIVES

2.1. Research Hypothesis

Considering that:

1) The dark maple syrup contains pigments and coloring products that are originated

from different browning reactions and that these products are easily absorbable on

active sites contained in matrices such as activated carbon;

2) The activated carbon of food grade is able to adsorb coloring pigments and products

which are similar to those found in dark maple syrup;

3) The use of activated carbon as a bleaching agent is easy to introduce in the food

industry, in general, as well as in the industry of maple products, in particular;

Thus:

It will be possible to use food grade activated carbon for bleaching unmarketable dark

maple syrup in order to make a product that falls into a category of maple syrups with a

high commercial value.

2.2. General objective

The general objective of the present research project is to discolor unmarketable low grade

dark maple syrup with activated carbon in order to make a product with light transmittance

similar to a marketable maple syrup.

22

2.2.1. Specific objectives

1) To achieve the general objective of this work, the first specific objective was aimed

to study the effect of different independent variables on the light transmittance of

the dark maple syrup measured at 560 nm:

Effect of the mixing time;

Effect of the concentration of the activated carbon;

Effect of the type of activated carbon;

Effect of the activated carbon mean particle size;

Effect of the stirring speed;

Effect of the working temperature.

2) A second specific objective consisted of applying the Langmuir, Freundlich and

Langmuir-Freundlich adsorption isotherms to describe the discoloration kinetics of

the dark maple syrup on activated carbon according to the best results obtained in

the first specific objective.

23

CHAPTER 3: MATERIALS, METHODS, RESULTS

AND DISCUSSION

Le présent mémoire de maîtrise est rédigé par insertion d’un article scientifique soumis

pour publication dans Food Bioscience, un journal international avec comité de lecture. Par

conséquent, la partie ``Matériels et méthodes`` est incluse dans ce chapitre.

25

Improvement of the color of low grade dark maple syrup

by adsorption on activated carbon and study of the

adsorption kinetics

Running title: Activated carbon to improvement color of low grade dark maple syrup

Bita Sadeghi-Tabatabai1,2, Amara Aït-Aissa1, 2, Mohammed Aïder*1, 2

1Department of Soil Sciences and Agro-Food Engineering, Université Laval, Quebec, Qc,

G1V 0A6, Canada

2Institute of Nutrition and Functional Foods (INAF), Université Laval, Quebec, Qc, G1V

0A6, Canada.

* Corresponding author

E-mail: mohammed.aider@fsaa.ulaval.ca

Tel: (418) 656-2131 # 4051

Fax: (418) 656-3723

26

Abstract

Low grade dark maple syrup was successfully discolored on activated carbon.

Several experimental parameters were tested, namely the mixing time (20, 40, 60 min),

concentration of the activated carbon (0.1, 0.3, 0.5 g/100 mL), type of activated carbon (I,

II, III), particle size (25, 50, 75 μm), stirring speed (200, 400, 600 rpm), and temperature

(40, 60, 80°C). The obtained results showed that the discoloration is optimal by applying

the parameters such as an agitation time of 40 min with an activated carbon of type III at a

concentration of 0.3 g/100 mL. These parameters yielded a light transmittance of 83.70 ±

0.21%, which ranks the syrup in the extra clear class. The results showed that among the

tested carbons, the adsorption on the type carbon of III followed the Langmuir, Freundlich

and Langmuir-Freundlich isotherms. Regarding the effect of the particle size, the obtained

results showed that a mean size of 25 µm with a stirring speed of 200 rpm and a working

temperature of 80°C was the most effective. The optimized conditions showed a good

adequacy with the Langmuir and Freundlich models. The discoloration process by using the

activated carbon of type III followed pseudo-second order kinetics.

Keywords: Maple syrup; Adsorption; Activated carbon, Adsorption isotherms. Kinetics.

27

Résumé

Dans ce travail, nous avons utilisé le charbon actif (trois types) pour décolorer le sirop

d'érable foncé, classé dans la catégorie ``Non retenu`` de la classification du Québec du

sirop d’érable. Nous avons testé l'efficacité de la rétention des pigments colorés du sirop

d'érable sur le charbon actif en grains et en poudre. Aussi, nous avons comparé les

différentes efficacités de ces matériaux. La première étape de nos essais expérimentaux a eu

pour but de suivre les cinétiques d'adsorption des pigments. Dans cette partie, plusieurs

paramètres expérimentaux ont été optimisés par utilisation d'un plan factoriel complet; à

savoir : le temps d'agitation (20,40, 60 min), la masse du charbon actif utilisée par 100 ml

de sirop (0.1, 0.3, 0.5 g), le type du charbon actif (I, II, III), le diamètre moyen des

particules du charbon (25, 50, 75 µm), la vitesse d'agitation (200, 400, 600 rpm) et la

température (40,60, 80 °C). La variable dépendante que nous avons considérée dans ce

projet est la transmittance de la lumière du sirop mesurée à 560 nm. La deuxième étape a

été consacrée sur l'étude du pouvoir adsorbant des trois types de charbons actifs utilisés

avec l’application des modèles de Langmuir, Freundlich et de Langmuir-Freundlich pour

décrire les cinétiques d’adsorption. Les résultats obtenus ont montré que la décoloration du

sirop d’érable foncé est optimale avec les paramètres suivants : temps d'agitation t = 40 mn,

masse du charbon actif ajouté m = 0.3 g et charbon actif de type III. Ces paramètres ont

donné une valeur de la transmittance la transmittance de la lumière à 560 nm de 83.7 ± 0.2

%; et qui classe le sirop dans la catégorie Extra clair. Ensuite, ce travail a montré que seul

le charbon actif de type III vérifiait à la fois une cinétique d’adsorption qui se décrit par les

isothermes de sorption de Langmuir, Freundlich et Langmuir-Freundlich. Finalement, un

autre plan d'expérience avait complété dans ce travail et qui portait sur l'optimisation de la

taille des particules du charbon et qui a montré qu’une granulométrie moyenne d = 25 µm

(mésopores) était la plus optimale pour décolore le sirop d’érable avec une agitation de 200

rpm à une température T = 80°C.

28

3.1. Introduction

Maple syrup is largely produced in North America by heat evaporation of maple sap

collected from maple sugar trees (Acer saccharum) during the early spring season (Clément

et al., 2010). Canada is the largest exporter of maple products in the world with 249 million

$ in 2012 and Quebec accounted for 94% of the Canadian maple products exported. In

Canada, the maple syrup is mainly classified according to the color by measuring its light

transmittance at 560 nm (Perkins and van den Berg, 2009). There are two types of

classification for maple syrup: the federal government classification and that of the

provincial governments. The Canadian Food Inspection Agency governs the quality of

maple products in Canada and is responsible for the federal classification of maple syrup

which can be classified as extra light, light, medium, amber and dark. The latter is generally

associated with a strong burnt caramel flavor and taste. Moreover, huge quantities of maple

syrup said ``unclassified`` are produced each year. This product is stored and large

quantities are accumulate from year to year, creating serious problems of management and

marketing. Indeed, gradually, as the season progresses, the fructose and glucose content

increases in the sap, while the sucrose content decreases slightly. Moreover, the content of

other natural compounds found in the sap is also changing during the season (amino acids

and minerals). These changes in the composition of the sap cause a change in the color and

flavor of maple syrup, mainly because of the occurred reaction between the reducing sugars

and amino acids of the sap (Danehy, 1986). Early in the season, the syrup is generally clear

with good sweet taste, corresponding to the syrup of the best quality. However, as the

season progresses, the syrup becomes darker and tastes caramelized sugar with less refined

flavor.

To increase the profitability of the maple syrup industry, it is important to

commercialize all the produced products, including the dark syrup called unclassified. To

achieve this objective, it is necessary to improve the product color and make it at least

amber or light. Moreover, the material or process used to achieve the color improvement

must also affect positively the sensor quality of the end product, namely its smell and taste.

Since maple syrup is a food product, the used material for color correction must be safe and

29

economically affordable. In this context, activated carbon (charcoal) seems to be an

appropriate decolorizing and taste/smell improving agent. However, the choice of the most

appropriate type of activated carbon for a particular application must be technologically

feasible because the achievement of the targeted objective will depend on different factors

such as the physical and chemical properties of the adsorbed material, proper functional

properties of the activated carbon and other experimental conditions that can play an

important role in the adsorption process (Agueda et al., 2011).

At the end of the 18th century, the adsorption properties of activated carbon were

observed. Then, the activated carbon was used for the first time in England in the sugar

industry in 1794 to improve the process efficiency and product quality (Harris, 1942).

However, the modern industrial production and the use of activated carbon were reported

for the first time in a patent deposed by Ostrejko in 1901 (Ostrejko, 1901). Today, the

activated carbon is used in several industrial applications; including gas and air cleaning,

purification and recovery of different materials and substances, environmental protection

for the removal of hydrocarbons and solvents (Xu et al., 2014). Furthermore, the activated

carbon is also used increasingly in the treatment of water, including drinking water,

groundwater, and wastewater. Its main role is to absorb dissolved organic impurities and

eliminate all substances that affect the smell, taste and color of the treated material

(Dubinin and Serpinsky, 1981; Liu et al., 2010; Ugurlu et al., 2008; Wood, 2002).

Furthermore, the activated carbon is widely applied for liquid discoloration, which is

particularly important in the pharmaceutical and food industry; including the maple syrup

industry (Li et al., 2013b; Senthil Kumar et al., 2010).

This paper presents both experimental and theoretical interpretation of the

mechanisms involved in maple syrup discoloration by activated carbon. The goal of this

study was to use food grade activated carbon as adsorption material to improve the color

and smell/taste of dark maple syrup in order to produce lighter syrup corresponding to

syrup of light or at least amber grade. Specifically, the effect of many experimental factors

such as the agitation time (X1), activated carbon mass in the sample (X2), and activated

carbon type (X3) on the syrup transmittance was studied by using a three level full factorial

experiment design. The kinetics of adsorption of the maple syrup pigments were interpreted

(discussed) by using two kinetic models: the pseudo-first-order and the pseudo-second-

30

order models. Kinetic parameters and correlation coefficients were also determined.

Moreover, the adsorption isotherm models of Langmuir, Freundlich and Langmuir-

Freundlich were used to evaluate the effect of the experimental parameters on the

performance of the activated carbon to adsorb the maple syrup coloration pigments.

3.2. Materials and Methods

3.2.1. Reagents and Samples

Dark, low grade (unclassified) maple syrup was purchase from a local maple syrup

farm, Quebec City, Canada. The activated carbon type I, II and IV were purchased from

Sigma Aldrich (Sigma-Aldrich, St. Louis, MO, USA). The activated carbon type III was

purchased from Fisher Scientific (Fisher Scientific, Waltham, MA, USA).

3.2.2. Characterization of the activated carbon

3.2.2.1. Mean particle size

The mean particle size of each activated carbon used in this study was determined

by the sieving method by using a series of sieves from the Canadian Standard Sieve Series

(W. S. Tyler Company, ON, Canada) according to the ASTM procedure (ASTM, 2010).

3.2.2.2. Scanning electron microscopy (SEM) and Energy

dispersive X-ray spectrometer (EDS)

Scanning electron microscopy (SEM) images of the activated carbon were taken by

using an electron microscope (Joel, JSM-840A, North Billerica, MA, USA) equipped with

an EDS energy dispersive X-ray spectrometer (PGT Instrument, model Avalon, Princeton,

NJ, USA). The EDS condition was set at 15 kV. The samples were first metalized by

coating with a thin gold / palladium layer in order to make the surface conductive and allow

the free flow of the excess electrons. This procedure is necessary to prevent the sample to

be charged when it is exposed to the SEM electron probe (Chou et al., 2008).

31

3.2.2.3. Bulk density

The apparent density of the activated carbon used in this work is calculated by the

tube method as adapted from the ASTM method D2854-09 (ASTM, 2014). A known

amount of activated carbon sample was weighed and poured into a test tube which was

taped with 10 strokes. Then, the resulted volume of the activated carbon in the sample was

read. Knowing the mass and the volume, the apparent density of each analyzed activated

carbon was determined.

3.2.3. Experimental procedure

The discoloration process used in this work is illustrated in Figure 7. To carry out

the experiments, three amounts of activated carbon (0.01, 0.03 or 0.05 g) were weighed and

introduced into a sample of 10 mL of maple syrup to yield a final concentration of 0.1, 0.3

and 0.5 g/100 mL. Then, the mixture was placed in a thermostatic bath (ThermoFisher

Scientific, model 1534258, NH, USA) at a temperature of 25°C with a low agitation of 200

rpm on a magnetic stirrer (IKA, model RW20DSI, Wilmington, NC, USA). The stirring

(mixing) time was set to 20, 40 and 60 min. At the end of the mixing time, the mixture was

first filtered by using a simple paper filter with a goal of removing the large particles of the

used activated carbon. The second filtration was carried out by using two syringe filters

with mesh size of 45 and 20 microns, respectively. Finally, the light transmittance of the

recovered samples was analyzed by a UV-Visible spectrophotometer (HP S/N 4582901633,

USA) at 560 nm (Corbella and Cozzolino, 2005).

3.2.4. Statistical modeling and adsorption isotherms

In this work, two blocks of experiments were carried out and each one was a three

level full factorial experimental design (3k) with k = 3 in triplicate. The polynomial

equation (Eq. 3.1) was used to model the response variable y as a function of the input

factors X’i.

2 2 2

1 1 3 1 2 3y = 11.61+ 4.55 X - 4.406 X X + 23.19 X + 23.16 X + 27.46 X (Eq. 3.1)

A second order regression equation was used to calculate the optimal values of all

parameters which can allow giving a maximal color improvement of the maple syrup. For

32

achieve this objective, it is necessary to solve the system of equations (Eqs. 3.2) by

deriving the predictive equation at each variable X1, X2 and X3.

1

1

2

2

3

3

y 0 X = 40 min

X

y 0 X = 0.03g

X

y 0 X = type III

X

(Eqs. 3.2)

In the present study, it has been hypothesized that the discoloration of the maple syrup

resulted from an adsorption mechanism of the coloring pigments on the surface of the

activated carbon. Thus, in order to obtain an adequate interpretation of the observed color

improvement of the maple syrup, the intensity of coloration of the syrup solution was

plotted as a function of adsorbed coloration. The data were plotted against the Langmuir,

Freundlich, and Langmuir-Freundlich adsorption isotherms, as shown in Table 4.

3.2.5. Experimental design and statistical analysis

In the first experimental block, a full factorial experimental design (33) was used

and all the experiments were carried out at ambient temperature (25 C). The independent

variables were as follow: agitation time (X1) (20, 40, 60 min); activated carbon

concentration (X2) (0.1, 0.3, 0.5%); and activated carbon type, (X3) (I, II, III). The second

experimental block was also carried out as a full factorial design with three independent

variables: temperature (X1) (40, 60, 80 C), type activated carbon mean size (X2) (25, 50,

75 microns) and agitation speed (X3) (200, 400, 600 rpm). The analysis of variance

(ANOVA) and normality Test (Shapiro-Wilk) were used to investigate the differences

between the mean values of the compared treatments at a 95% significant level by using the

SigmaPlot v. 11 software (Systat Software Inc, San Jose, Ca, USA) and Maple Software

v.14 (Maplesoft, Waterloo, ON, Canada). The isotherm model constants (Langmuir,

Freundlich and Langmuir-Freundlich), average relative errors (%), and coefficient of

determination (R2) based on the actual deviation between the experimental points and the

predicted values were estimated by using SigmaPlot v.11. All experiments were carried out

at least in triplicate and mean values were used for different calculations and comparisons.

33

3.3. Results and Discussion

3.3.1. Characteristics of the used activated carbons

The particle size analysis served to determine the size distribution of the particles

constituting the different used activated carbons. The total carbon mass which was sifted

was 200 g and the particle size distribution was in the range up to 300 μm. The particle size

distribution was dependent of the form of the carbon (powder or grain), and of the particle

shape (spherical or heterogeneous shape). It has been found that the used carbons did not

present a uniform size distribution and have heterogeneous shapes including some spherical

form. Moreover, the particle size of the activated carbon of type III have particle size

diameter up to 150 µm (Figure 8).

The different activated carbons used in this work were inert carbonaceous materials.

Some of them have highly developed intrinsic porosity which gives them good adsorbing

properties facilitating the fixation on their surface of the colored pigments present in the

dark maple syrup used (Wang and Yuan, 2014). This feature is due to the micro pores

present in these carbons. The number and distribution of these micro pores can significantly

affect the adsorption capacity of these materials. Unlike to the activated carbon type IV, the

micro pores distribution is much pronounced on the surfaces of the activated carbon of type

I, II and III (Figure 9). The structure of the activated carbon of type III seems to be highly

developed then the other types of the used carbons. The pore structure increases the specific

surface of the activated carbon which can reach approximate values of 1.500 m²/g of

carbon. This specific surface has an effect of increasing the carbon adsorptive properties.

For the texture, the active carbons of type I, II and IV have an amorphous texture which is

made of graphite microcrystal in different interconnected form. The activated carbon of

type III has a crystalline structure with sites which are favorable for good adsorptive

properties. In addition, each microcrystal comprises a stack of several crystalline layers

with a high degree of porosity (Figure 9).

The structural analysis showed also that the different activated carbons used contain

different types of elements in different amounts. They are mainly consisted of carbon.

However, besides carbon, the activated carbon of type I consists of some volatile matters,

in particular oxygen. The other composition is represented by ash material composed of

different minerals such as calcium, which was found in the activated carbon of type III. The

34

presence of Ca can affect the adsorption properties of this activated carbon, as reported in

(Li et al., 2013a). The observed the gold and palladium were from the metalized samples

that were used as coating to form the thin gold/palladium layer in order to make the carbon

surface conductive and allow the free flow of the excess electrons during the Energy

dispersive X-ray spectrometric analysis (Figure 10).

The results obtained for the bulk density showed that the values corresponding to

the activated carbons of type I, II, and III are almost similar. These carbons are used in the

form of powder to discolor the dark maple syrup. The activated carbon of type IV was

different from the other carbons and was characterized by a high bulk density which may

be due to its initial granular form. In addition, the observed differences of the bulk densities

can be attributed to the differences observed in the particle shape of the used activated

carbons. Applied to the targeted adsorption application of this study, the spherical form of

the activated carbon particles will be more favorable because this form present low bulk

density and punctual inter particle contact (Bhargavi et al., 2011) (Figure 11).

3.3.2. Effect of the concentration and type of the added activated

carbon

The evolution of the maple syrup light transmittance at 560 nm as a function of the

mixing time at different concentrations of the activated carbon added is shown in Figure

12. Statistical analysis of the obtained data showed a significant effect (p < 0.001) of this

independent variable and the plotted values of the dependent variable (light transmittance)

followed a behavior that can be described by a second order polynomial function. It has

been observed that the light transmittance of the treated maple syrup increased by

increasing the concentration of the activated carbon added. This can be explained by the

increasing of the contact surface between the adsorbent and the adsorbate which yielded a

high amount of adsorption of the colored pigments. In fact, it has been already reported that

the higher the contact area is, the higher the absorption reaction is (Hall et al., 1966). In

Figure 12a which corresponds to the data obtained by using the activated carbon of type I,

it can be seen that the light transmittance increased from 11.11 ± 0.25% up to 31.39 ±

0.30% in the case of using 0.1% of activated carbon; and up to 64 ± 0.3% in the case of

using 0.3% g. However, addition of 0.5% of activated carbon resulted in final syrup with

light transmittance of 56 ± 0.32% which is lower than the value obtained with 0.3%. At the

35

other hand, the Figure 12b shows that the transmission range varies between 11 and 17%

in the case of using activated carbon of type II. At the end of the mixing time of 60 min, the

light transmittance values of the syrup were 15.11 ± 0.25%, 15.65 ± 0.3% and 16.63 ±

0.25%, for activated concentration added of 0.1, 0.3 and 0.5%, respectively. This result

showed the non-significant effect (p > 0.05) of the activated carbon of type II

concentration. Finally, the Figure 12c shows that the transmittance range varies between

23.42 and 61.51% in the case of using the activated carbon of type III. The final syrup light

transmittances obtained after 60 min treatment were 23.42 ± 0.31, 83.86 ± 1.15, and 61.51

± 0.51% for a concentration of the added activated carbon of 0.1, 0.3 and 0.5%,

respectively. This type of activated carbon gave the highest light transmittance of the final

maple syrup, which is probably due to its large surface area (Figure 9). The results

obtained with the activated carbon of type IV (Figure 12d) were not significantly different

from those obtained with the activated carbon of type II.

The optimized results showed that the optimal activated carbon concentration to be

added to the dark maple syrup in order to obtain a final product with significantly improved

color is 0.3%. Thus, the use of 0.05% activated carbon is not necessary since the occurred

adsorption phenomenon was saturated at 0.03%. This saturation can be explained by the

chemisorption process which is more dominant in the present case. Indeed, it has been

reported that chemisorption is a common process in the adsorption of dyes on different

adsorbents (Ho et al., 2005; Ho and McKay, 1998; Ofomaja, 2007). Finally, it has been

found that the use of the activated carbon type I gives a syrup which can be classified as

amber with light transmittance ranging between 27-43.9% or as medium with a light

transmittance of 44-61%. The activated carbon of type II and IV did not improve the color

of the syrup gives. The use of the activated carbon of type III did not improve the color of

the syrup when it was used in a concentration of 0.1%, but it yielded syrup that can be

classified as light when the carbon concentration was 0.5% or extra clear light when the

active carbon concentration was 0.3%.

The evolution of the light transmittance of the treated maple syrup as a function of

different activated carbon types is shown in Figure 13. The lines represent the regression

polynomial of second order. In Figures 13(a, b, c), it is observed that the transmittances

increased with the increasing of the mass of the activated carbons according to their

36

different type. The light transmittance was carbon type dependent and increased with the

type the used activated carbon following the classification IV, II, I, III. The highest light

transmittance obtained by using the activated carbon of the type III is summarized in Table

5. In all cases, the transmittances which obtained at 20 and 40 min by using the activated

carbon type III are higher than that obtained with the carbon type I at 60 min. Indeed, this

can be explained by the fact that the colored pigments are more adsorbed by using the

activated carbon type III.

3.3.3. Effect of the mixing stirring time

The evolution of the light transmittance of the maple syrup as a function of the

mixing time with different activated carbon types is shown in Figure 14. The Figure 14a

shows that by using the activated carbon of type I, the effect of the mixing time on the

adsorption of the colored pigments was not significant. The highest light transmittance

recorded with 0.1% of the activated carbon of type I was 37.82 ± 0.12% after 40 min, with

0.3%, the light transmittance reached a value of 64 ± 0.11% after 60 min, and finally the

use of the 0.5% activated carbon gave a light transmittance of 68.02 ± 0.12% after 40 min

mixing. Figure 14b shows that the activated carbon of type II absorbs the colored pigments

with a different manner then the activated carbon type I as a function of the mixing time.

By using 0.1 and 0.3% of activated carbon, the light transmittance increased linearly as a

function of the mixing time, even if the final product remained dark since its light

transmittance passed from 11.11 ± 0.25% to 16.66 ± 0.25%. At the same time, the obtained

results showed that at 0.5% of activated carbon, the effect of the mixing time was not

significant on the color of the treated maple syrup with a mean value of 16.40 ± 0.25%. In

the Figure 14c which corresponds to the use of the activated carbon of type III, the

obtained results shows that the adsorption kinetics reached a maximum at a treatment time

of 40 min with a maximum light transmittance of 83.70 ± 0.21%. Beyond this time, the

adsorption was saturated. However, at a fixed concentration of the added activated carbon,

the effect of time was the lowest at 20 min treatment and with no significant difference

between 40 and 60 min of mixing.

The observed behaviors can be explained as follows: the transfer of colored

pigments of maple syrup toward the surface of the activated carbon follows four steps,

37

which may be independent each other, and in which the importance of time is very

significant (Ozkaya, 2006; Vargas et al., 2012). The first step represents the migration of

the coloring pigments from the syrup to the surface of the activated carbon. The second is

the diffusion through the interparticle spaces which corresponds to the external diffusion

phase. The third step is the intraparticle diffusion, and the last one represents the surface

chemical reaction between the surface features of the adsorbent and the active groups of the

maple syrup pigments. It should be noted that the first step can be controlled with a good

stirring and mixing time, while the last is quite fast, suggesting that the diffusion processes

are the limiting steps that control the adsorption phenomenon (Myers, 1968).

3.3.4. Effect of the temperature, particle size and mixing speed

The effect of the temperature (40, 60, 80°C) on the adsorption of the pigments from

the dark maple syrup by using the activated carbon of type III is shown in Figure 15. The

increase of the temperature resulted in a significant (p < 0.001) increase of the light

transmittance of the maple syrup. This increase of the temperature caused an increase of the

adsorption reaction by increasing the average velocity of the molecules. As a result, the

molecules of the colored pigments acquired sufficient kinetic energy to produce an

effective collisions with the adsorption surface of the activated carbon (Khalfaoui et al.,

2003; Srihari and Das, 2008; Srivastava et al., 2006). Effect of the particle size was also

significant (p < 0.001) and Figures 15a-c show that the increase of the transmittance varies

according to the activated carbon particles used. By using the particle size of 25 µm, the

highest light transmittance reached an average value of 78.37 ± 0.15%. For the same type

of the activated carbon (type III), the use of a particle size of 50 and 75 µm yielded in

average light transmittance of 67.48 ± 0.10 and 62 ± 0.35%, respectively. Thus, it seems

that the adsorption increases by increasing the specific surface of the activated carbon

which corresponds to the lowest particle size (Juárez-Galan et al., 2009).

The effect of particle diameter of activated carbon type III on the adsorption of the

pigments from the dark maple syrup is shown in Figure 16. Unlike to the data plotted on

Figures 16a-b, the Figure 16c shows a maximum discoloration of maple syrup which

corresponds to a light transmittance of 68 ± 0.10% which is obtained under the

experimental conditions of a mean particle size of 25 µm, working temperature of 80°C and

38

stirring speed of 200 rpm. The Figure 16c shows two interesting trends. The first was up to

200 rpm with a rapid rise of the light transmittance values, followed by the formation of a

steady state between 200 and 600 rpm.

The effect of mixing speed on the adsorption of maple syrup coloring pigments on

the surface of the activated carbon of type III is presented on Figure 17 on which it can be

seen that the light transmittance of the treated syrup is inversely proportional to the increase

of the mixing speed. This can be explained by the fact that the increase of the mixing speed

may cause desorption of some already adsorbed colored pigments. The optimized results

showed an optimum stirring speed of 200 rpm which can be considered as sufficient to

promote an adequate contact between the activated carbon particles and colored pigments

(molecules) of the dark maple syrup (Myers and Prausnitz, 1965).

3.3.5. Statistical modeling of the discoloration process

The parabolic shape of the obtained response surface suggests that there is a

maximum yield of the discoloration which is given by the coordinates of the highest point

of the surface (Figure 18). In what follows, the isoresponse will be plotted with a purpose

to find the conditions which give the highest discoloration yield of the dark maple syrup.

Therefore, we will find the area where this condition is verified. As the number of the

independent variables is high (3), the study of all factors at the same time is not easy and in

order to simplify the study, cuts by setting a variable and plotting the isoresponse curves in

the plane of two other variables will be done. On the other hand, the isoresponse plotted

curves predicts the maximum value of the performance and movement of the display area

as a function defining the optimum operating conditions, in the other hand. Thus, the results

obtained by varying the three parameters (X1, X2 and X3) are shown in Figure 19. By

observing the curves, it can be seen that the best response in terms of maximization of

maple syrup discoloration is obtained when the following conditions are met:

For X1 = (-1, 0, +1); X2 varies from 0 to +1 and X3 varies from 0 to +1; X2 varies from 0 to

+1 and X3 varies from 0 to -1; X2 varies from 0 to -1 and X3 varies from 0 to +1; X2 varies

from 0 to -1 and X3 varies from 0 to -1.

39

Then, for X2 = (-1, 0, +1); X1 varies from 0 to +1 and X3 varies from 0 to +1, X1 varies

from 0 to +1 and X3 varies from 0 to -1, X1 varies from 0 to -1 and X3 varies from 0 to -1;

X1 varies from 0 to -1 and X3 varies from 0 to -1.

Finally, for X3 = (-1, 0, +1); X1 varies from 0 to +1 and X2 varies from 0 to +1; X1 varies

from 0 to +1 and X2 varies from 0 to -1; X1 varies from 0 to -1 and X2 varies from 0 to +1;

X1 varies from 0 to -1 and X2 varies from 0 to -1.

3.3.5.1. Adsorption isotherm models

The Figure 20 shows the application of isotherm models which used to predict the

discoloration of maple syrup under different experimental conditions which is considered to

be a result of adsorption phenomenon. The experimental results were analyzed by using

three two-parametric isotherm models of Freundlich and Langmuir, and one three-

parameteric Langmuir-Freundlich isotherm model. The main characteristic of the Langmuir

adsorption isotherm is its simplicity and the physical meaning of the KL and Qm parameters.

The value of KL is related to the strength of interaction between the adsorbed molecules and

the solid surface and Qm value expresses the amount of solute per gram of solid fixed

surface which is considered as totally covered by a monomolecular layer. This model is

verified by a monolayer adsorption and demonstrates the heterogeneity of the surface.

Regarding the use of the activated carbon of type I, Figure 20a shows that the experimental

points are not well fitted by the Langmuir adsorption isotherm model. This result can be

explained by the absence of interactions between the adsorbed species and the adjacent

surface of activated carbon. Similarly, the difference could come from either significant

lateral interactions, or a distribution of more complicated sites. In the case where activated

carbon of types II and III, Figures 20b-c show that the experimental results are verified by

the Langmuir adsorption isotherm. Unlike to the activated carbon of type I, the activated

carbons of type II and III provide an adsorbed monolayer of colored pigments of dark

maple syrup. This can be explained by the fact that the activated carbons II and III have

heterogeneous surfaces and all their adsorption sites are energetically equivalent. Moreover,

the obtained coefficients of determination are 0.84, 0.96, and 0.99 for the activated carbon

I, II and III, respectively. The calculation of the quantities of the colored pigments per gram

that are fixed on the activated carbon surface which considered as totally covered by a

40

monomolecular layer vary depending of the type of the used activated carbon (I, II and III).

These quantities are 0.72 10-5, 2.64 10-5, and 3.89 10-5g for the activated carbon of type I,

II, and III, respectively.

The obtained results were also verified if they fit the Freundlich adsorption isotherm

model. This choice is justified by the fact that this adsorption isotherm model is linked to a

constant indicating the adsorption capacity of the activated carbon, as well as to an

empirical constant which is related to the magnitude of the driving force of the adsorption

phenomenon. The use of the activated carbon of type I, II (Figures 20a-b) show a weak

adequacy of the Freundlich adsorption isotherm model with the experimental results. This

can be explained by the fact that the coloring pigments (molecules) of the dark maple syrup

do not necessarily follow a multilayer adsorption behavior. In the case when the activated

carbon of type III was used (Figure 20c), the experimental results adequately fitted the

Freundlich adsorption isotherm model. The coefficient of determination was equal to 0.73

and 0.78 in the case of the use of activated carbons of type I and II, respectively, and 0.97

in the case when the type III was used. Also, comparing the constants which serve to

indicate the adsorption capacity of the adsorbent, the constant related to the activated

carbon of type III (Kf = 1.95 mg L-1 g-1) is significantly higher than those of the activated

carbons of type I and II which are 0.98 and 0.99 mg L-1 g-1, respectively.

Furthermore, Figure 20c shows that the experimental results adequately fit all the

Langmuir, Freundlich, and Langmuir-Freundlich adsorption isotherms by using the

activated carbon of type III to discolor the dark, low grade maple syrup. This type of

activated carbon (type III) absorbs molecules of the colored pigments by monolayer and

multilayer adsorption mechanisms. Sips has shown in 1948 that the monolayer and

multilayer adsorption is a complex phenomenon as there is superposing of a saturation

adsorption energy on the active sites along a curved homogeneous Langmuir adsorption

isotherm model and on heterogeneous sites according to the Freundlich isotherm adsorption

model (Sips, 1948). This superposition of phenomena can be interpreted in terms of the

distribution of the coloring pigments on the surface of the activated carbon used. Part of

these pigments diffuses into the activated carbon and the concentration of this fraction

follows the Freundlich's law. Another part will be adsorbed on the surface of activated

carbon, and this process will be described by the Langmuir adsorption isotherm model. The

41

coefficients of determination obtained in Figure 20c for the Langmuir, Freundlich and

Langmuir-Freundlich adsorption isotherm models by using the activated carbon of type III

are 0.99, 0.98, and 0.99, respectively.

3.3.5.2. Dark maple syrup discoloration kinetic order

The kinetic orders of the adsorption of the colored pigments of the dark maple syrup

on the activated carbon of type III are given in Table 6 and are graphically shown on

Figure 21. The constant of the pseudo-first order was determined by extrapolating the plot

of log (qe-qt) versus time (t). The value of K1 obtained was 0.0138 min-1. Figure 21a shows

the concentration of the coloring particles adsorbed on the activated carbon of type III. It is

found that the retention rate of the coloring pigments increased with increasing the reaction

time. This phenomenon took place on two different steps which can be distinguished by

their slopes. The first step was fast and occurred between 0 and 40 min, while the second

step was slow between 40 and 60 min of treatment. This step can be characterized by a

balance between the adsorbed molecules on the surface of the activated carbon and

adsorbed ones. The major part of the coloring molecules which were transferred to the

activated carbon of type III was observed in the first 40 min of the treatment which was

confirmed by the resulting light transmittance of 83.7 ± 0.2%. In addition, the experimental

results do not fit the model of the first order kinetic. These observations led to conclude that

the adsorption of the colored pigments of the dark maple syrup by using the activated

carbon of type III does not represent a controlled diffusion process, since it does not follow

the first-order equation given by Corbett (Corbett, 1972). Figure 21b shows the application

of the kinetic model of pseudo-second order to describe the results obtained by the

adsorption of the colored pigments of the dark maple syrup on the activated carbon of type

III. The plot of (t/qt) versus time (t) allowed determining, by extrapolation, the constant of

pseudo-second order at different contact time between the syrup and the used activated

carbon. The value of K2 obtained is 0.0049 L.mg-1.mn-1. In view of these results, it appears

that the amount of the adsorbed molecules increases with increasing the mixing time.

Furthermore, the experimental results adequately fit the pseudo-second order kinetic. Thus,

the result leads to conclude that the adsorption process followed the model that can be

described by a pseudo-second order kinetic.

42

Conclusion

In this work, different activated carbons were used to improve the color of a dark

maple syrup. Scanning electron microscopy (SEM) analysis of the different activated

carbons used showed that they are different from each other by their specific and contact

surface area, as well as by their roughness. Moreover, the Energy dispersive X-ray

spectrometry (EDS) showed that the chemical composition of the activated carbons used is

also different from each other.

By using an activated carbon defined as carbon of type III, the adsorption of the

coloring pigments from the dark maple syrup led to a total elimination of the dark

coloration and the process yielded syrup with light transmittance of 83.70 ± 0.2%. This

syrup can be classified as extra clear, according the Canadian classification of maple syrup.

This result was obtained under the following operating conditions: activated carbon of type

III used at 0.3% and mixing time of 40 min. The optimized experimental conditions

showed that the adsorption of the coloring pigments of the surface of the activated carbon

was favored by a particle size of 25 µm under an operating temperature of 80°C and mixing

speed of 200 rpm.

The adsorption kinetic of the discoloration process of the dark maple syrup under

different experimental parameters was verified against different adsorption isotherm

models. Two-parameteric Langmuir and Freundlich isotherm models, as well as a three-

parameter Langmuir-Freundlich isotherm model were tested. It has been shown that the

discoloration of the dark maple syrup by using the activated carbon of type III can be

predicted by the Langmuir, Freundlich, and the Langmuir-Freundlich isotherm models,

dependently of the experimental conditions used. Unlike to the kinetics of pseudo-first

order, it has been shown that the discoloration of the dark syrup maple by using the

activated carbon of type III can be described by a pseudo-second order kinetic.

Acknowledgements

Financial support from NSERC-CRSNG is acknowledged. The authors would like

to express their entire gratitude to Mrs. Diane Gagnon for the technical support.

43

Conflict of Interest Statement

We state that there is no conflict of interest for this article.

45

CONCLUSION GÉNÉRALE ET PERSPÉCTIVES

L’objectif principal du présent projet était atteint et l’hypothèse de recherche

vérifiée et confirmée. En effet, le dispositif expérimental utilisé dans ce travail nous a

permis d’améliorer la couleur foncée d’un sirop d’érable non commercialisable et de le

ramener au grade d’un sirop clair. Quant à l’hypothèse de recherche qui suggérait que le

charbon actif de grade alimentaire pourrait décolorer par adsorption le sirop d’érable, alors,

celle-ci a été confirmée.

Sur le plan de nouvelles connaissances, et bien que le charbon actif soit déjà connu

comme étant un adsorbant, le présent projet se distingue par l’application de différentes

isothermes de sorption pour décrire le phénomène associé à la décoloration du sirop

d’érable foncé via l’adsorption de ses pigments de coloration qui sont formés suite au

traitement thermique dont il a fait l’objet. En effet, le pouvoir adsorbant des trois types de

charbons actifs utilisés a fait l’objet d’une validation avec l’application des modèles de

Langmuir, Freundlich et de Langmuir-Freundlich pour décrire les cinétiques d’adsorption.

Les résultats obtenus ont montré que la décoloration du sirop d’érable foncé est optimale

avec un temps d'agitation de 40 min, une concentration du charbon actif de type III de 0.3%

et charbon actif de type III ayant une granulométrie moyenne de 25 µm et utilisé à une

température de 80°C accompagnée d’une agitation à 200 rpm. Ces paramètres ont donné

une valeur de la transmittance la lumière à 560 nm de 83.7 ± 0.2 %; ce qui classe le sirop

dans la catégorie Extra claire.

Comme perspective de ce projet, il serait intéressant, voire même pertinent, de

valider à une échelle industrielle les résultats obtenus dans ce travail. De cette manière, le

transfert technologique vers l’industrie du sirop d’érable sera très facile et pourrait

contribuer à augmenter la rentabilité globale de ce secteur économique de grande

importance pour le Québec, surtout, dans le milieu rural. Ce sirop pourrait alors trouver une

meilleure façon d’être commercialisé, tant sur le marché national qu’en exportation. Ainsi,

les recettes générées contribueront à consolider le rôle important de l’industrie acéricole

dans l’économie du Québec, en particulier, et celle du Canada, en général.

47

Table 4: Adsorption isotherm models used to describe the color removal from dark maple

syrup.

Models Equations Linear equations

Langmuir (Langmuir, 1918) m L e

e

L e

Q K Cq =

1 + K C

e m L e m

1 1 1

q Q K C Q

Freundlich (Freundlich, 1906) 1/n

e L eq = K C

e L e

1ln q = ln K + ln C

n

Langmuir-Freundlich (Sips, 1948)

n

m L ee n

L e

Q (K C )q =

1 + (K C )

1/n

e m L e m

1 1 1

q Q (K C ) Q

48

Table 5: Variation of transmittances at different stirring time and different mass of the

activated carbon (type III).

Time (min)

Activated carbon type III

0.01 g 0.03g

0.05g

20

59.87% ± 0.1

71.91% ± 0.12

83.07% ± 0.13

40

63.42% ± 0.10

73.86% ± 0.75

80.51% ± 0.10

60

31.39% ± 0.10

64.00% ± 0.7

66.00% ± 0.8

49

Table 6: Pseudo-first and pseudo-second order equations used to describe the adsorption

kinetic models of maple syrup discoloration.

Models Equations Linear equations

Pseudo-first order (Corbett, 1972)

t

1 e t

dqk q - q

dt 1

e t e

klog q - q =log (q )- t

2.303

Pseudo-second order

(Ho and McKay, 1998)

2t

2 e t

dqk q - q

dt 2

t 2 e e

t 1 1 = + t

q k q q

50

Captions to Figures

Figure 7: Schematic representation of the experimental set-up.

Figure 8: Activated carbon particle size distribution.

Figure 9: Scanning electron micrographs of the surface activated carbon particles used in

maple syrup discoloration.

Figure 10: Energy dispersive X-ray spectrometer of different type of activated carbon.

Figure 11: Bulk density comparison of different activated carbon.

Figure 12: Transmittance as a function of time at different activated carbon concentrations

and different activated carbons: (a) Type I, (b) Type II, (c) Type III, (d) Type IV.

Figure 13: Transmittance as a function of activated carbon mass at different activated

carbon and different agitation time: (a) 20 min, (b) 40 min, (c) 60 min.

Figure 14: Transmittance as a function of activated carbon mass at different stirring time

and different activated carbon. (a) Type I, (b) Type II, (c) Type III, (d) Type IV.

Figure 15: Transmittance as a function of particle diameters of activated carbon type III at

different working temperatures and different stirring speed: (a) 200 rpm, (b) 400 rpm, (c)

600 rpm.

Figure 16: Transmittance as a function of stirring speed at different particle size of

activated carbon III and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C.

Figure 17: Transmittance as a function of particle size of activated carbon III at different

stirring speed and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C.

Figure 18: Response surface at X1 = 0, X2 (-1, 0, +1), and X3 (-1, 0, +1).

Figure 19: Iso-response curve at different level of X1 (-1, 0, +1), X2 (-1, 0, +1) and X3 (-1,

0, +1).

51

Figure 20: Coloration concentration of the maple syrup solution as a function of coloration

concentration adsorbed by activated carbon at different adsorption isotherm type. (a)

activated carbon type I, (b) activated carbon type II, and (c) activated carbon type III.

Figure 21: Application of Kinetic models for the dark maple syrup adsorption by using

activated carbon type III. (a) Pseudo-first order; (b) Pseudo-second order.

52

Figure 7: Schematic representation of the experimental set-up.

53

Figure 8: Activated carbon particle size distribution.

54

Figure 9: Scanning electron micrographs of the surface activated carbon particles used in

maple syrup discoloration.

55

Figure 10: Energy dispersive X-ray spectrometer of different type of activated carbon.

56

Figure 11: Bulk density comparison of different activated carbon.

57

Figure 12: Transmittance as a function of time at different activated carbon

concentrations and different activated carbons: (a) Type I, (b) Type II, (c) Type III, (d)

Type IV.

58

Figure 13: Transmittance as a function of activated carbon mass at different activated

carbon and different agitation time: (a) 20 min, (b) 40 min, (c) 60 min.

59

Figure 14: Transmittance as a function of activated carbon mass at different stirring time

and different activated carbon. (a) Type I, (b) Type II, (c) Type III, (d) Type IV.

60

Figure 15: Transmittance as a function of particle diameters of activated carbon type III

at different working temperatures and different stirring speed: (a) 200 rpm, (b) 400 rpm,

(c) 600 rpm.

61

Figure 16: Transmittance as a function of stirring speed at different particle size of

activated carbon III and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C.

62

Figure 17: Transmittance as a function of particle size of activated carbon III at different

stirring speed and different working temperatures: (a) 40°C, (b) 60°C, (c) 80°C.

63

Figure 18: Response surface at X1 = 0, X2 (-1, 0, +1), and X3 (-1, 0, +1).

64

Figure 19: Iso-response curve at different level of X1 (-1, 0, +1), X2 (-1, 0, +1) and X3

(-1, 0, +1).

65

Figure 20: Coloration concentration of the maple syrup solution as a function of

coloration concentration adsorbed by activated carbon at different adsorption isotherm

type. (a) type I, (b) type II, and (c) type III.

66

Figure 21: Kinetic models of the adsorption by using activated carbon type III. (a)

Pseudo-first order; (b) Pseudo-second order.

67

RÉFÉRENCES

AAC, (2007). Statistics of maple syrup production. Agriculture and Agri-Food Canada.

AAC, (2014). Statistics of maple syrup production. Agriculture and Agri-Food Canada.

ACIA, (2015). Produits de l'érable. Agence canadienne d'inspection des aliments.

Agueda, V.I., Crittenden, B.D., Delgado, J.A., Tennison, S.R., (2011). Effect of channel

geometry, degree of activation, relative humidity and temperature on the performance of

binderless activated carbon monoliths in the removal of dichloromethane from air.

Separation and Purification Technology 78(2), 154-163.

AlOthman, Z.A., Habila, M.A., Ali, R., Abdel Ghafar, A., El-din Hassouna, M.S., (2014).

Valorization of two waste streams into activated carbon and studying its adsorption

kinetics, equilibrium isotherms and thermodynamics for methylene blue removal. Arabian

Journal of Chemistry 7(6), 1148-1158.

Altmann, J., Ruhl, A.S., Zietzschmann, F., Jekel, M., (2014). Direct comparison of

ozonation and adsorption onto powdered activated carbon for micropollutant removal in

advanced wastewater treatment. Water Research 55(0), 185-193.

Ames, J.M., (2009). Dietary Maillard Reaction Products: Implications for Human Health

and Disease. Czech Journal of Food Science 27, S66-S69.

Angin, D., (2014). Utilization of activated carbon produced from fruit juice industry solid

waste for the adsorption of Yellow 18 from aqueous solutions. Bioresource Technology

168(0), 259-266.

Angın, D., Altintig, E., Köse, T.E., (2013). Influence of process parameters on the surface

and chemical properties of activated carbon obtained from biochar by chemical activation.

Bioresource Technology 148(0), 542-549.

Asadi, M., (2007). Beet-sugar handbook. John Wiley and Sons, Inc., Hoboken, New Jersey.

ASTM, (2010). D2862-10 Standard Test Method for Particle Size Distribution of Granular

Activated Carbon. ASTM International, West Conshohocken, PA.

ASTM, (2014). Standard Test Method for Apparent Density of Activated Carbon. ASTM

International, West Conshohocken, PA.

Ayranci, E., Duman, O., (2006). Adsorption of aromatic organic acids onto high area

activated carbon cloth in relation to wastewater purification. Journal of Hazardous

Materials 136(3), 542-552.

68

Baccar, R., Sarrà, M., Bouzid, J., Feki, M., Blánquez, P., (2012). Removal of

pharmaceutical compounds by activated carbon prepared from agricultural by-product.

Chemical Engineering Journal 211–212(0), 310-317.

Baléo, J.-N., Subrenat, P.L.C.A., (2000). Numerical simulation of flows in air treatment

devices using activated carbon cloths filters. Chemical Engineering Science 55(10), 1807-

1816.

Bandosz, T.J., Kante, K., (2015). Chapter 34 - Spent Coffee-Based Activated Carbons:

Production, Properties, and Environmental Applications, in: Preedy, V.R. (Ed.), Coffee in

Health and Disease Prevention. Academic Press, San Diego, pp. 311-317.

Bañuelos, J.A., El-Ghenymy, A., Rodríguez, F.J., Manríquez, J., Bustos, E., Rodríguez, A.,

Brillas, E., Godínez, L.A., (2014). Study of an Air Diffusion Activated Carbon Packed

Electrode for an Electro-Fenton Wastewater Treatment. Electrochimica Acta 140(0), 412-

418.

Bayram, E., Ayranci, E., (2012). Electrosorption based waste water treatment system using

activated carbon cloth electrode: Electrosorption of benzoic acid from a flow-through

electrolytic cell. Separation and Purification Technology 86(0), 113-118.

Bhargavi, R., Kadirvelu, K., Kumar, N.S., (2011). Vapor Phase Adsorption of Homologous

Aliphatic Ketones on Activated Spherical Carbon. International Journal of Environmental

Sciences 1(5), 938-947.

Bristow, M., S. Isaacs, N., (1999). The effect of high pressure on the formation of volatile

products in a model Maillard reaction. Journal of the Chemical Society, Perkin

Transactions 2(10), 2213-2218.

Calisto, V., Ferreira, C.I.A., Oliveira, J.A.B.P., Otero, M., Esteves, V.I., (2015). Adsorptive

removal of pharmaceuticals from water by commercial and waste-based carbons. Journal of

Environmental Management 152(0), 83-90.

Carabasa-Giribet, M., Ibarz-Ribas, A., (2000). Kinetics of colour development in aqueous

fructose systems at high temperatures. Journal of the Science of Food and Agriculture

80(14), 2105-2113.

Çelebi, I., (2006). Color formation in wheat starch based glucose syrups and use of

activated carbons for sugar decolorization A thesis of Master, Natural and Applied Sciences

of Middle East Technical University, 27-33.

69

Chou, C., Formenti, P., Maille, M., Ausset, P., Helas, G., Harrison, M., Osborne, S.,

(2008). Size distribution, shape, and composition of mineral dust aerosols collected during

the African Monsoon Multidisciplinary Analysis Special Observation Period 0: Dust and

Biomass-Burning Experiment field campaign in Niger, January 2006. Journal of

Geophysical Research: Atmospheres 113(D23), D00C10.

Clarke, R.J., (2003). COFFEE | Decaffeination, in: Caballero, B. (Ed.), Encyclopedia of

Food Sciences and Nutrition (Second Edition). Academic Press, Oxford, pp. 1506-1511.

Clément, A., Lagacé, L., Panneton, B., (2010). Assessment of maple syrup physico-

chemistry and typicity by means of fluorescence spectroscopy. Journal of Food

Engineering 97(1), 17-23.

Corbella, E., Cozzolino, D., (2005). Short Communication: The use of visible and near

infrared spectroscopy to classify the floral origin of honey samples produced in Uruguay.

Journal of Near Infrared Spectroscopy 13(2), 63-68.

Corbett, J.F., (1972). Pseudo first-order kinetics. Journal of Chemical Education 49(10),

663.

Danehy, J.P., (1986). Maillard Reactions: Nonenzymatic Browning in Food Systems with

Special Reference to the Development of Flavor, in: C.O. Chichester, E.M.M., Schweigert,

B.S. (Eds.), Advances in Food Research. Academic Press, pp. 77-138.

Danish, M., Hashim, R., Ibrahim, M.N.M., Sulaiman, O., (2014). Optimized preparation for

large surface area activated carbon from date (Phoenix dactylifera L.) stone biomass.

Biomass and Bioenergy 61(0), 167-178.

Diban, N., Ruiz, G., Urtiaga, A., Ortiz, I., (2007). Granular activated carbon for the

recovery of the main pear aroma compound: Viability and kinetic modelling of ethyl-2,4-

decadienoate adsorption. Journal of Food Engineering 78(4), 1259-1266.

Dong, J.-J., Ye, J.-H., Lu, J.-L., Zheng, X.-Q., Liang, Y.-R., (2011). Isolation of antioxidant

catechins from green tea and its decaffeination. Food and Bioproducts Processing 89(1),

62-66.

Dubinin, M.M., Serpinsky, V.V., (1981). Isotherm equation for water vapor adsorption by

microporous carbonaceous adsorbents. Carbon 19(5), 402-403.

Dziedzic, S.Z., Kearsley, M.W., (1984). Glucose syrups: Science and technology. Elsevier

Applied Science Publishers.

70

Ekasari, I., Jongen, W.M.F., Pilnik, W., (1986). Use of a bacterial mutagenicity assay as a

rapid method for the detection of early stage of Maillard reactions in orange juices. Food

Chemistry 21(2), 125-131.

Eskin, N.A.M., (1990). 5 - Biochemistry of Food Processing: Browning Reactions in

Foods, in: Eskin, N.A.M. (Ed.), Biochemistry of Foods (Second Edition). Academic Press,

San Diego, pp. 239-296.

Esteves, I.A.A.C., Lopes, M.S.S., Nunes, P.M.C., Mota, J.P.B., (2008). Adsorption of

natural gas and biogas components on activated carbon. Separation and Purification

Technology 62(2), 281-296.

Filteau, M., Lagacé, L., LaPointe, G., Roy, D., (2010). Seasonal and regional diversity of

maple sap microbiota revealed using community PCR fingerprinting and 16S rRNA gene

clone libraries. Systematic and Applied Microbiology 33(3), 165-173.

Filteau, M., Lagacé, L., LaPointe, G., Roy, D., (2011). Correlation of maple sap

composition with bacterial and fungal communities determined by multiplex automated

ribosomal intergenic spacer analysis (MARISA). Food Microbiology 28(5), 980-989.

Filteau, M., Lagacé, L., LaPointe, G., Roy, D., (2012). Maple sap predominant microbial

contaminants are correlated with the physicochemical and sensorial properties of maple

syrup. International Journal of Food Microbiology 154(1–2), 30-36.

Frazier, R.A., (2004). Food Protein Analysis: Quantitative Effects on Processing: R. K.

Owusu-Apenten, Marcel Dekker, 2002, XI+463 pp. ISBN 0-8247-0684-6. Food Chemistry

85(2), 315.

Galiatsatou, P., Metaxas, M., Arapoglou, D., Kasselouri-Rigopoulou, V., (2002). Treatment

of olive mill waste water with activated carbons from agricultural by-products. Waste

Management 22(7), 803-812.

Gao, Y., Yue, Q.-Y., Sun, Y.-Y., Xiao, J.-N., Gao, B.-Y., Zhao, P., Yu, H., Optimization of

high surface area activated carbon production from Enteromorpha prolifra with low-dose

activating agent. Fuel Processing Technology(0).

Guo, C., Chen, Y., Chen, J., Wang, X., Zhang, G., Wang, J., Cui, W., Zhang, Z., (2014).

Combined hydrolysis acidification and bio-contact oxidation system with air-lift tubes and

activated carbon bioreactor for oilfield wastewater treatment. Bioresource Technology

169(0), 630-636.

71

Hadi, P., To, M.-H., Hui, C.-W., Lin, C.S.K., McKay, G., (2015a). Aqueous mercury

adsorption by activated carbons. Water Research 73(0), 37-55.

Hadi, P., Xu, M., Ning, C., Sze Ki Lin, C., McKay, G., (2015b). A critical review on

preparation, characterization and utilization of sludge-derived activated carbons for

wastewater treatment. Chemical Engineering Journal 260(0), 895-906.

Hall, K.R., Eagleton, L.C., Acrivos, A., Vermeulen, T., (1966). Pore- and Solid-Diffusion

Kinetics in Fixed-Bed Adsorption under Constant-Pattern Conditions. Industrial &

Engineering Chemistry Fundamentals 5(2), 212-223.

Harris, E.W., (1942). Activated Carbon in Sugar Refining. Industrial & Engineering

Chemistry 34(9), 1057-1060.

Hernández, S.P., Chiappero, M., Russo, N., Fino, D., (2011a). A novel ZnO-based

adsorbent for biogas purification in H2 production systems. Chemical Engineering Journal

176–177(0), 272-279.

Hernández, S.P., Scarpa, F., Fino, D., Conti, R., (2011b). Biogas purification for MCFC

application. International Journal of Hydrogen Energy 36(13), 8112-8118.

Ho, Y.S., Chiang, T.H., Hsueh, Y.M., (2005). Removal of basic dye from aqueous solution

using tree fern as a biosorbent. Process Biochemistry 40(1), 119-124.

Ho, Y.S., McKay, G., (1998). Kinetic Models for the Sorption of Dye from Aqueous

Solution by Wood. Process Safety and Environmental Protection 76(2), 183-191.

Hodge, J.E., (1953). Dehydrated Foods, Chemistry of Browning Reactions in Model

Systems. Journal of Agricultural and Food Chemistry 1(15), 928-943.

Holden, P., (1998). Anglian Water membrane hybrid system for the soft drinks industry.

Desalination 118(1–3), 267-271.

Houston, D.L., (1980). United States Standards for Grades of Maple Syrup. United stated

Department of Agriculture.

Juárez-Galan, J.M., Silvestre-Albero, A., Silvestre-Albero, J., Rodríguez-Reinoso, F.,

(2009). Synthesis of activated carbon with highly developed “mesoporosity”. Microporous

and Mesoporous Materials 117(1–2), 519-521.

Kallio, H., Rine, S., Pangborn, R.M., Jennings, W., (1987). Effect of heating on the

headspace volatiles of Finnish birch syrup. Food Chemistry 24(4), 287-299.

72

Khalf, M., Dabour, N., kheadr, E., Fliss, I., (2010). Viability of probiotic bacteria in maple

sap products under storage and gastrointestinal conditions. Bioresource Technology

101(20), 7966-7972.

Khalfaoui, M., Knani, S., Hachicha, M.A., Lamine, A.B., (2003). New theoretical

expressions for the five adsorption type isotherms classified by BET based on statistical

physics treatment. Journal of Colloid and Interface Science 263(2), 350-356.

Koffi, K., Labrie, S., Genois, A., Aït Aissa, A., Aïder, M., (2014). Contribution to the

development of a method of maple sap soft drink stabilization by electro-activation

technology. LWT - Food Science and Technology 59(1), 138-147.

Kumar, C.G., (2003). Activated charcoal: a versatile decolorization agent for the recovery

and purification of alkaline protease. World Journal of Microbiology and Biotechnology

19(3), 243-246.

Kyzas, G.Z., Deliyanni, E.A., Modified activated carbons from potato peels as green

environmental-friendly adsorbents for the treatment of pharmaceutical effluents. Chemical

Engineering Research and Design(0).

Lagacé, L., Jacques, M., Mafu, A.A., Roy, D., (2006). Compositions of maple sap

microflora and collection system biofilms evaluated by scanning electron microscopy and

denaturing gradient gel electrophoresis. International Journal of Food Microbiology 109(1–

2), 9-18.

Laksameethanasana, P., Somla, N., Janprem, S., Phochuen, N., (2012). Clarification of

sugarcane juice for syrup production. Procedia Engineering 32(0), 141-147.

Li, G., Shang, J., Wang, Y., Li, Y., Gao, H., (2013a). Effect of calcium on adsorption

capacity of powdered activated carbon. Journal of Environmental Sciences 25, Supplement

1(0), S101-S105.

Li, Y., Du, Q., Liu, T., Peng, X., Wang, J., Sun, J., Wang, Y., Wu, S., Wang, Z., Xia, Y.,

Xia, L., (2013b). Comparative study of methylene blue dye adsorption onto activated

carbon, graphene oxide, and carbon nanotubes. Chemical Engineering Research and Design

91(2), 361-368.

Liu, Q.-S., Zheng, T., Wang, P., Jiang, J.-P., Li, N., (2010). Adsorption isotherm, kinetic

and mechanism studies of some substituted phenols on activated carbon fibers. Chemical

Engineering Journal 157(2–3), 348-356.

73

Mailler, R., Gasperi, J., Coquet, Y., Deshayes, S., Zedek, S., Cren-Olivé, C., Cartiser, N.,

Eudes, V., Bressy, A., Caupos, E., Moilleron, R., Chebbo, G., Rocher, V., Study of a large

scale powdered activated carbon pilot: Removals of a wide range of emerging and priority

micropollutants from wastewater treatment plant effluents. Water Research(0).

Manley, D., (2000). 10 - Sugars and syrups, in: Manley, D. (Ed.), Technology of Biscuits,

Crackers and Cookies (Third Edition). Woodhead Publishing, pp. 112-129.

Margot, J., Kienle, C., Magnet, A., Weil, M., Rossi, L., de Alencastro, L.F., Abegglen, C.,

Thonney, D., Chèvre, N., Schärer, M., Barry, D.A., (2013). Treatment of micropollutants in

municipal wastewater: Ozone or powdered activated carbon? Science of The Total

Environment 461–462(0), 480-498.

Marsh, H., Rodríguez-Reinoso, F., (2006). Chapter 8 - Applicability of Activated Carbon,

in: Rodríguez-Reinoso, H.M. (Ed.), Activated Carbon. Elsevier Science Ltd, Oxford, pp.

383-453.

Masuda, J., Fukuyama, J., Fujii, S., (1999). Influence of concurrent substances on removal

of hydrogen sulfide by activated carbon. Chemosphere 39(10), 1611-1616.

Mestre, A.S., Pires, R.A., Aroso, I., Fernandes, E.M., Pinto, M.L., Reis, R.L., Andrade,

M.A., Pires, J., Silva, S.P., Carvalho, A.P., (2014). Activated carbons prepared from

industrial pre-treated cork: Sustainable adsorbents for pharmaceutical compounds removal.

Chemical Engineering Journal 253(0), 408-417.

Morselli, M.F., (1980). Maple syrup containers: effect of storage on the stability of three

table grades. Agricultural Experiment Station, University of Vermont. Burlington, USA.

Mudoga, H.L., Yucel, H., Kincal, N.S., (2008). Decolorization of sugar syrups using

commercial and sugar beet pulp based activated carbons. Bioresource Technology 99(9),

3528-3533.

Myers, A.L., (1968). Adsorption of gas mixtures-a thermodynamic approach. Industrial &

Engineering Chemistry 60(5), 45-49.

Myers, A.L., Prausnitz, J.M., (1965). Thermodynamics of mixed-gas adsorption. AIChE

Journal 11(1), 121-127.

Ofomaja, A.E., (2007). Kinetics and mechanism of methylene blue sorption onto palm

kernel fibre. Process Biochemistry 42(1), 16-24.

74

Ostrejko, R., (1901). Method for the production and regeneration of carbon with steam for

decoloring. German patent number # 136792.

Ozkaya, B., (2006). Adsorption and desorption of phenol on activated carbon and a

comparison of isotherm models. Journal of Hazardous Materials 129(1–3), 158-163.

Pendyal, B., Johns, M.M., Marshall, W.E., Ahmedna, M., Rao, R.M., (1999a). The effect of

binders and agricultural by-products on physical and chemical properties of granular

activated carbons. Bioresource Technology 68(3), 247-254.

Pendyal, B., Johns, M.M., Marshall, W.E., Ahmedna, M., Rao, R.M., (1999b). Removal of

sugar colorants by granular activated carbons made from binders and agricultural by-

products. Bioresource Technology 69(1), 45-51.

Perkins, T.D., van den Berg, A.K., (2009). Chapter 4 Maple Syrup—Production,

Composition, Chemistry, and Sensory Characteristics, in: Steve, L.T. (Ed.), Advances in

Food and Nutrition Research. Academic Press, pp. 101-143.

Pipatmanomai, S., Kaewluan, S., Vitidsant, T., (2009). Economic assessment of biogas-to-

electricity generation system with H2S removal by activated carbon in small pig farm.

Applied Energy 86(5), 669-674.

Przepiórski, J., (2006). Chapter 9 Activated carbon filters and their industrial applications,

in: Teresa, J.B. (Ed.), Interface Science and Technology. Elsevier, pp. 421-474.

Purlis, E., (2010). Browning development in bakery products – A review. Journal of Food

Engineering 99(3), 239-249.

Québec, F.d.p.a.d., (2015). La classification du sirop d’érable

http://www.siropderable.ca/Classification.aspx Consulté le 03/02/2015.

Raisi, A., Aroujalian, A., (2007). Reduction of the glucose syrup browning rate by the use

of modified atmosphere packaging. Journal of Food Engineering 80(1), 370-373.

Ramırez-Jiménez, A., Garcıa-Villanova, B., Guerra-Hernández, E., (2000).

Hydroxymethylfurfural and methylfurfural content of selected bakery products. Food

Research International 33(10), 833-838.

Rapp, J.M., Crone, E.E., (2015). Maple syrup production declines following masting.

Forest Ecology and Management 335(0), 249-254.

75

Razvigorova, M., Budinova, T., Petrov, N., Minkova, V., (1998). Purification of water by

activated carbons from apricot stones, lignites and anthracite. Water Research 32(7), 2135-

2139.

Rodriguez-Illera, M., Ramires Ferreira Da Silva, A., Boom, R.M., Janssen, A.E.M.,

Recovery of a bioactive tripeptide from a crude hydrolysate using activated carbon. Food

and Bioproducts Processing(0).

Ruhl, A.S., Zietzschmann, F., Hilbrandt, I., Meinel, F., Altmann, J., Sperlich, A., Jekel, M.,

(2014). Targeted testing of activated carbons for advanced wastewater treatment. Chemical

Engineering Journal 257(0), 184-190.

Saha, B.C., Hayashi, K., (2001). Debittering of protein hydrolyzates. Biotechnology

Advances 19(5), 355-370.

Sardella, F., Gimenez, M., Navas, C., Morandi, C., Deiana, C., Sapag, K., (2015).

Conversion of viticultural industry wastes into activated carbons for removal of lead and

cadmium. Journal of Environmental Chemical Engineering 3(1), 253-260.

Senthil Kumar, P., Ramalingam, S., Senthamarai, C., Niranjanaa, M., Vijayalakshmi, P.,

Sivanesan, S., (2010). Adsorption of dye from aqueous solution by cashew nut shell:

Studies on equilibrium isotherm, kinetics and thermodynamics of interactions. Desalination

261(1–2), 52-60.

Siebert, K.J., (2013). 18 - Instrumental assessment of the sensory quality of beer, in:

Kilcast, D. (Ed.), Instrumental Assessment of Food Sensory Quality. Woodhead Publishing,

pp. 547-564.

Sips, R., (1948). On the Structure of a Catalyst Surface. The Journal of Chemical Physics

16(5), 490-495.

Sitthikhankaew, R., Predapitakkun, S., Kiattikomol, R., Pumhiran, S., Assabumrungrat, S.,

Laosiripojana, N., (2011). Comparative Study of Hydrogen Sulfide Adsorption by using

Alkaline Impregnated Activated Carbons for Hot Fuel Gas Purification. Energy Procedia

9(0), 15-24.

Snyder, S.A., Adham, S., Redding, A.M., Cannon, F.S., DeCarolis, J., Oppenheimer, J.,

Wert, E.C., Yoon, Y., (2007). Role of membranes and activated carbon in the removal of

endocrine disruptors and pharmaceuticals. Desalination 202(1–3), 156-181.

76

Soto, M.L., Moure, A., Domínguez, H., Parajó, J.C., (2011). Recovery, concentration and

purification of phenolic compounds by adsorption: A review. Journal of Food Engineering

105(1), 1-27.

Srihari, V., Das, A., (2008). The kinetic and thermodynamic studies of phenol-sorption

onto three agro-based carbons. Desalination 225(1–3), 220-234.

Srivastava, V.C., Swamy, M.M., Mall, I.D., Prasad, B., Mishra, I.M., (2006). Adsorptive

removal of phenol by bagasse fly ash and activated carbon: Equilibrium, kinetics and

thermodynamics. Colloids and Surfaces A: Physicochemical and Engineering Aspects

272(1–2), 89-104.

Strachowski, P., Bystrzejewski, M., (2015). Comparative studies of sorption of phenolic

compounds onto carbon-encapsulated iron nanoparticles, carbon nanotubes and activated

carbon. Colloids and Surfaces A: Physicochemical and Engineering Aspects 467(0), 113-

123.

Suárez-Quiroz, M.L., Alonso Campos, A., Valerio Alfaro, G., González-Ríos, O.,

Villeneuve, P., Figueroa-Espinoza, M.C., (2014). Isolation of green coffee chlorogenic

acids using activated carbon. Journal of Food Composition and Analysis 33(1), 55-58.

Sun, Y., Webley, P.A., (2010). Preparation of activated carbons from corncob with large

specific surface area by a variety of chemical activators and their application in gas storage.

Chemical Engineering Journal 162(3), 883-892.

Sy, A.P., (1908). History, manufacture and analysis of maple products. Journal of the

Franklin Institute 166(4), 249-280.

Tammaro, M., Salluzzo, A., Perfetto, R., Lancia, A., (2014). A comparative evaluation of

biological activated carbon and activated sludge processes for the treatment of tannery

wastewater. Journal of Environmental Chemical Engineering 2(3), 1445-1455.

Ugurlu, M., Gurses, A., Acikyildiz, M., (2008). Comparison of textile dyeing effluent

adsorption on commercial activated carbon and activated carbon prepared from olive stone

by ZnCl2 activation. Microporous and Mesoporous Materials 111(1–3), 228-235.

Updyke, K.M., Nguyen, T.B., Nizkorodov, S.A., (2012). Formation of brown carbon via

reactions of ammonia with secondary organic aerosols from biogenic and anthropogenic

precursors. Atmospheric Environment 63(0), 22-31.

77

Vanderhaegen, B., Neven, H., Verachtert, H., Derdelinckx, G., (2006). The chemistry of

beer aging – a critical review. Food Chemistry 95(3), 357-381.

Vargas, D.P., Giraldo, L., Moreno-Piraján, J.C., (2012). CO2 Adsorption on Activated

Carbon Honeycomb-Monoliths: A Comparison of Langmuir and Tóth Models.

International Journal of Molecular Sciences 13(7), 8388-8397.

Vuong, Q.V., Golding, J.B., Nguyen, M.H., Roach, P.D., (2013). Preparation of

decaffeinated and high caffeine powders from green tea. Powder Technology 233(0), 169-

175.

Wang, W., Yuan, D., (2014). Mesoporous carbon originated from non-permanent porous

MOFs for gas storage and CO2/CH4 separation. Sci. Rep. 4.

Wang, Y., Zhu, J., Huang, H., Cho, H.-H., Carbon nanotube composite membranes for

microfiltration of pharmaceuticals and personal care products: Capabilities and potential

mechanisms. Journal of Membrane Science(0).

Wild, A.D., Yanai, R.D., (2015). Soil nutrients affect sweetness of sugar maple sap. Forest

Ecology and Management 341(0), 30-36.

Wood, G.O., (2002). Review and comparisons of D/R models of equilibrium adsorption of

binary mixtures of organic vapors on activated carbons. Carbon 40(3), 231-239.

Wood, W.F., Brandes, J.A., Foy, B.D., Morgan, C.G., Mann, T.D., DeShazer, D.A., (2012).

The maple syrup odour of the “candy cap” mushroom, Lactarius fragilis var. rubidus.

Biochemical Systematics and Ecology 43(0), 51-53.

Worch, E., (1991). Prediction of mixture adsorption in fixed-bed adsorbers Pt. 1:

Mathematical model Chemical Technology 43, 111-113.

Xiao, Y., Wang, S., Wu, D., Yuan, Q., (2008a). Catalytic oxidation of hydrogen sulfide

over unmodified and impregnated activated carbon. Separation and Purification

Technology 59(3), 326-332.

Xiao, Y., Wang, S., Wu, D., Yuan, Q., (2008b). Experimental and simulation study of

hydrogen sulfide adsorption on impregnated activated carbon under anaerobic conditions.

Journal of Hazardous Materials 153(3), 1193-1200.

Xu, J., Chen, L., Qu, H., Jiao, Y., Xie, J., Xing, G., (2014). Preparation and characterization

of activated carbon from reedy grass leaves by chemical activation with H3PO4. Applied

Surface Science 320(0), 674-680.

78

Yaylayan, V.A., (2003). Recent Advances in the Chemistry of Strecker Degradation and

Amadori Rearrangement: Implications to Aroma and Color Formation. Food Science and

Technology Research 9(1), 1-6.

Yuan, T., Li, L., Zhang, Y., Seeram, N.P., (2013). Pasteurized and sterilized maple sap as

functional beverages: Chemical composition and antioxidant activities. Journal of

Functional Foods 5(4), 1582-1590.