236 JOURNAL OF FOOD SCIENCE—Vol. 67, Nr. 1, 2002 © 2002 Institute of Food Technologists

Food Engineering and Physical Properties

A Novel Technique for theDecolorization of Sugarcane JuiceM. OKUNO AND H. TAMAKI

ABSTRACT: A novel technique for the decolorization of sugarcane juice has been developed. In this method, thecoloration caused by polyphenols during the refining of cane sugar was removed by treatment with octadecylsilyl-silicagel. The efficiency of color removal was nearly 90%.

Keywords: sugarcane juice, polyphenols, octadecylsilyl-silicagel, decolorization

Introduction

PRODUCED IN PROCESSING SUGAR, SUGARCANE JUICE CON-tains a variety of polyphenols, such as flavonoids (Paton

and others 1985; Smith and Paton 1985), phenolic acids (Pa-ton 1992), phenolic glucosides (Palla 1982), and phenylpro-panoids (Nakasone and others 1996). These compounds arethe main source of colorants, essentially considered impuri-ties. Removal of these polyphenols is generally done by usingbone char. However, newer factories are currently using ion-exchange resins because bone char regeneration is costly.Due to the difficult regeneration process for high-color sugarsyrups by ion-exchange resins, many studies on the effectiveregeneration of these resins have been done (Bento 1997;Bento 1998). Furthermore, since much brine/caustic liquidwaste is discharged when ion-exchange resins are regenerat-ed, efforts have been made to reduce these various wastes(Stacey and John 1997).

Octadecylsilyl-silicagel (ODS) is widely used in reverse-phase chromatography as a strong adsorbent of polyphe-nols. ODS can be regenerated by using alcohol, which caneasily be recovered by evaporation. Hence, if ODS is used asthe decolorizer of sugarcane juice, no liquid wastes will beproduced from the clarification system.

The objective of this study was to decolorize sugarcanejuice by removing polyphenols with ODS adsorption, thenrecover these important polyphenol compounds from allfractions of the sugarcane juices.

Materials and Methods

THE ODS CARTRIDGE (SEP-PAK, VAC 35 CC, 10 G, C18 CAR-tridge) was purchased from Waters Corp. (Milford, Mass.,

U.S.A.). An ultrafiltration unit (Model UHP150K) with a stir-rer was purchased from Advantec Toyo Corp. (Tokyo, Ja-pan). The ultrafiltration membrane was an Amicon YM100membrane with molecular weight cut-off of 100,000 (Milli-pore Corp., Bedford, Mass., U.S.A.). Sugarcane extract (des-ignated as MSX-1), containing polyphenols at high concen-trations, was kindly provided by the Mitsui Sugar Co. Ltd.’sDevelopment and Research Group, Chigasaki Laboratory(Chigasaki, Japan). The Folin-Ciocalteu reagent was pur-chased from Nacalai Tesqu Corp. (Kyoto, Japan). The waterused was purified with a Millipore Elix 3. The other chemicalreagents and solvents were of analytical grade and used with-out further purification.

Commercially available sugarcane of the ‘F160 variety’was obtained from a field in an Okinawa prefecture. Prior to

use, the milled juice was frozen and stored at –20 °C.A solid phase extraction technique was used to recover

the polyphenols in the sugarcane. To determine the volumeof juice for ODS treatment, loading tests on the Sep-Pak car-tridges were carried out by using MSX-1 Sugarcane Extractas a model of the polyphenols in sugarcane. The ODS car-tridge was activated, and a 0.1% MSX-1 Sugarcane Extractaqueous solution was loaded onto the cartridge. Then, ab-sorbance (OD340nm) of the elution (CO) was measured andplotted (CO/CI) as a function of the elution volume. Here, CIdenotes OD340nm of the 0.1% MSX-1 solution.

ODS treatmentTo remove insoluble impurities, the following treatments

were conducted: the frozen sugarcane juice was defrosted,and centrifuged at 17000 x g for 15 min. The supernatant wasthe centrifuged juice (CJ).

Ultrafiltration is effective for clarifying sugarcane juice(Kishihara and others 1989; Kishihara and others 1993). CJwas subjected to ultrafiltration and the ultrafiltered juice (UJ)was then subjected to ODS treatment.

An ODS cartridge was conditioned with pure water beforeuse. The UJ (1000 ml) was loaded onto the ODS cartridge at aflow rate of 8.3 ml/min. The eluate was designated SugarFraction (SF). The cartridge was washed with 120 ml of purewater. These washings (SWF) were combined with SF and themixture was concentrated to 57.5° brix in vacuo to obtainsyrup. The syrup was next subjected to a crystallization test.The residue on the cartridge was eluted with 170 ml of 20%or 50% ethanol, and the eluates (PF1 and PF2, respectively)were concentrated to dryness. The cartridge was regenerat-ed with 120 ml of pure water. A schematic diagram of theprocess is presented in Figure 1. The operation was carriedout 50 times.

Crystallization of sucroseThe syrup was subjected to a crystallization test by using

an automatic laboratory boiling pan, as reported previouslyby Kishihara and others 1994. The first obtained crystalswere called A-sugar. The mother liquid was called A-molas-ses. The crystallization was carried out 3 times and B-sugar,C-sugar, B molasses, and C molasses were obtained, respec-tively (Table 1)

Analytical methods Polyphenol was determined using Folin-Ciocalteu re-

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Decolorizing sugarcane juice…

agent, according to the method of Singleton and others(1965). Gallic acid was used as a standard.

The color value was measured at OD420nm, and calculat-ed according to the method of the International Commissionfor Uniform Methods of Sugar Analysis (ICUMSA 1994). Thevalue was expressed as ICUMSA Units (IU). Decolorizationwas calculated by the following equation:

Decolorization (%) = {( color value 0 - color value 1)/colorvalue 0} x 100

color value 0: color value before decolorizationcolor value 1: color value after decolorizationThe potassium, calcium, and magnesium contents of sug-

ar juice, before and after ODS treatment, were determinedby inductively coupled plasma spectrometry (ShimadzuICPS-1000 III) with sucrose solution as a matrix.

Results and Discussion

THE ADSORPTION CAPACITY OF ODS AND DESORPTION CON-ditions were examined by using the commercial MSX-1

Sugarcane Extract as a model of polyphenols in sugarcanejuice. As a result of preliminary experiments, the concentra-tion of polyphenols in sugarcane juice was found to be ap-proximately 0.1%. From this, the concentration of MSX-1Sugarcane Extract was adjusted to 0.1%, and the solution wasloaded onto the ODS cartridge. The OD340nm of the elution(CO) was measured and the CO/CI ratio plotted as a functionof the elution volume (Figure 2). The CO/CI ratio was 0.1, 0.3,0.66, and 0.91 after 1000, 2000, 3000, and 4000 ml elutions, re-spectively. It is preferred to obtain juice with as low a colorvalue as possible and to treat sugarcane juice in as large avolume as possible. A 0.1 CO/CI ratio is equal to 90% decol-orization. From these results, the treatment volume was de-termined as 1000 ml.

Stepwise elution was used, since sugarcane juice contains

polyphenols of diverse polarity. The cane juice was clarifiedaccording to the schematic diagram shown in Figure 1. Theoperation described in Figure 1 was carried out 50 times toevaluate the life span of the ODS cartridge. The color valueaverage for UJ and SF was 4226 and 376 IU, respectively. De-colorization (%) was maintained at about 90% after 50 repe-titions (Figure 3). In another experiment performed in ourlaboratory, ODS was compared with ion-exchange resin forits ability to decolorize and for its life span using raw syrup.

The recovery of sucrose by crystallization is consideredan important index of juice clarification. The mineral contentof the juice is also an important index.

To evaluate the clarification, the syrup (concentrate of SFand SWF) was subjected to a crystallization test. Photographs

Figure 1—Diagram of clarification of sugarcane juice

Figure 2—Loading test of MSX-1 sugarcane extract of ODScartridge Co: OD340nm of outlet solution from the car-tridge, CI: OD340nm of inlet solution to the cartridge

Table 1—Color values of the sugars and molasses

Color Value (IU) Color Value (IU)

A-sugar 48 A-molasses 726B-sugar 99 B-molasses 1510C-sugar 342 C-molasses 3053Granulated sugar < 10Raw sugar 3860

Figure 3—Repetition loading test

Food Engineering and Physical Properties

Decolorizing sugarcane juice…

of A-sugar, granulated sugar, and raw sugar are shown in Fig-ure 4. A-sugar had a good shape and little color.

The mineral content of the juice before and after ODStreatment is shown in Table 2. Most of the minerals werefound to remain after this treatment.

As mentioned above, ODS treatment did not remove min-erals. It was therefore assessed that these minerals do not in-hibit the crystallization of sugar. The color value of the sug-ars is shown in Table 2. The color value of A-sugar was below50 IU (equivalent to most of the refined sugar available onthe market). To obtain refined sugar, 2 types of factories arerequired, namely, a raw sugar factory and a sugar refinery. Itis possible for the refinery process to be omitted and obtainwhite sugar.

Even for C-molasses, the color value was smaller than forraw sugar. C-molasses from a sugar factory or refinery areused in various kinds of fermentation as raw materials. How-ever, the highly colored fermentation wastes can cause prob-lems. The results of this study indicated that the ODS meth-od, as described in this paper, can be used to eliminate thiswaste problem.

After the juice was treated with ODS, the adsorbedpolyphenols were sequentially desorbed with 20 and 50%ethanol solutions (Figure 1). The total concentration of thepolyphenols in each fraction was determined as mentionedabove and the results are shown in Table 3. The recoveries ofPF1 and PF2 were 28 and 7%, respectively. The main compo-nent of PF1 contains phenylpropanoids and their glucosides;the main component of PF2 contains flavonoids and their C-glycosides (Yoshida and others 2000). These compounds ex-hibit strong antioxidant activity (Yoshida and others 2000).The recovered polyphenols could be useful as antioxidants infoods. Although more than 50% of the polyphenols moved tothe sugar fractions (SF and SWF), the remainder seemed tohave no negative effect on the color quality.

ODS treatment discharges little waste because ethanol is

Table 2—Mineral contents before and after ODS treatment

K Ca Mg

Before ODS treatment (g/100g solid) 1.6 0.19 0.11After ODS treatment (g/100g solid) 1.3 0.17 0.10

Table 3—Total polyphenols and the recovery

TotalVolume Concentration polyphenol *Polyphenol

Fraction (ml) (%) (mg) recovery (%)

UJ 1002 0.034 341 100SF 1010 0.017 172 50SWF 122 0.019 23 7PF1 170 0.057 97 28PF2 167 0.014 23 7

*Polyphenol recovery (%) was calculated based on the UJ

Figure 4—Photograph of sugar crystals

used for regenerating ODS. Thus it is possible to recover etha-nol from PF1, PF2, and ethanol waste as described in Figure 1.

Conclusions

THE ODS TREATMENT PROPOSED IN THIS PAPER WAS VERY EF-fective for clarification of sugarcane juice. A-sugar ob-

tained from the juice had a pale color with 48 IU of color val-ue. It may be possible to omit the refining step in the pro-duction of sugar. Even the color value of C-molassesproduced by this method was smaller than that of conven-tional raw sugar. Therefore, C-molasses could be used as araw material for fermentation without colored waste. Thepolyphenols recovered from the ODS could conceivably beused as an antioxidant in food. However, there are manytechnical improvements needed before commercial practice.Methods proposed in this study may realize a non-generatedwaste, or “green process,” in the production of sugar.

ReferencesBento L. 1997. Regeneration of decolorizing ion exchange resins: a new ap-

proach. Zuckerind 122:304-310.Bento L. 1998. Ion exchange resins for decolorization. Int Sugar J 100(1191):111-

117.[ICUMSA] International Commission for Uniform Methods of Sugar Analysis

( Japanese Language Version). 1994. Shimyodo, Tokyo: ICUMSA. GS1-7.Kishihara S, Tamaki H, Fujii S, Komoto M. 1989. Clarification of technical sugar

solutions through a dynamic membrane formed on a porous ceramic tube. JMembrane Sci 41:103-114.

Kishihara S, Tamaki H, Wakiuchi N, Fujii S. 1993. Effect of ultrafiltration of factorysugar solution on growth of sucrose crystals. Int Sugar J 1135:273-277.

Kishihara S, Fujii S. 1994. Development of an automatic laboratory boiling pan.Int Sugar J 96(1151):451-456.

Nakasone Y, Takara K, Wada K, Tanaka J, Yogi S, Nakatani N. 1996. Antioxidativecompounds isolated from kokuto, non-centrifugal cane sugar. Biosci BiotechBiochem 60(10):1714-1716.

Palla G. 1982. Isoration and identification of phenolics glucoside in liquid sug-ars from cane molasses. J Agric Food Chem 30:764-766.

Paton NH, Smith P, Mabry TJ. 1985. Identification of flavonoid compounds inHPLC separation of sugarcane colorants. Int Sugar J 87(1043):213-215.

Paton NH. 1992. Sugarcane phenolics and first expressed juice colour: Part II.Concentration of phenolics in sugarcane and colour of first expressed juice.Int Sugar J 94(1123):157-160.

Singleton VL, Rossi J.A. 1965. Colorimetry of total phenolics with phosphomolyb-dic-phosphotungstic acid reagents. Am J Enol Vitic 16(145):144-158.

Smith P, Paton NH. 1985. Sugarcane Flavonoids. Sugar Technol Rev 12:117-142.Stacey E, John C. 1997. Trials on continuous ion exchange decolorization. Int

Sugar J 99(1181):215-224.Yoshida A, Kanehira S, Tamaki H, Wakiuchi N, Kishihara S. 2000. Nippon Nogeik-

agaku Kaishi 74(3):264.MS 20001596 Submitted 12/15/00, Revised 5/2/01, Accepted 5/24/01, Received

5/31/01

We express our deepest thanks to Chigasaki Laboratory, Mitsui Sugar Co. Ltd., for providingMSX-1 Sugarcane Extract and to Dr. Y. D. Hang and Dr. G. S. Stoewsand for their helpfuladvice and encouragement.

Author Okuno is with the Graduate School Science and Technology, andauthor Tamaki is with the Faculty of Agriculture at Kobe University, 1Rokkodaicho, Nada-ku, Kobe 657-8501, Japan. Direct inquiries to authorTamaki (E-mail: tamaki@kobe-u.ac.jp).