Chapter A Detail Chemistry of Coffee and Its Analysis

Chapter

A Detail Chemistry of Coffee andIts AnalysisHemraj Sharma

Abstract

This review article highlights the detailed chemistry of coffee including itscomponents; chemical constituents like carbohydrates, proteins, lipids, and caf-feine; aromatic principles; oil and waxes; and minerals and acids. The high extent ofcaffeine can be found in the coffee plants; hence, in the second part of the study,various analytical methods are designed for the proper identification, separation,optimization, purification, and determination of caffeine present in coffee, tea, andmarketed coffee. These analytical methods are appropriated for the separation andquantification of caffeine. The various analytical methods include spectroscopymethods like UV, IR, and NMR spectroscopy; chromatographic methods like paper,TLC, column, HPLC, and gas chromatography; and hyphenated techniques likeLC–MS, GC–MS, and GC–MS/MS. This article compares and contrasts the amountof caffeine by various analytical methods.

Keywords: caffeine, spectrophotometer, chromatography, hyphenated techniques,electrochemical methods

1. Introduction

Coffee consists of ripe seeds of Coffea arabica Linn., belonging to familyRubiaceae. Coffee extracted from coffee bean is also present in crimson fruits iscompletely removed, and the spermoderm is removed, occasionally. The seeds ofbotanical genus Coffea may be raw, roasted, whole, or ground. The prepared drinkthrough such coffee seeds is also called as coffee. Among 70 species of coffee, onlythree are cultivated. 75% of the world’s production of coffee is provided by Coffeaarabica, about 25% by Coffea canephora, and less than 1% by Coffea liberica andothers. Generally, coffee is cultivated at the altitude of 1000–2000 [1]. It is indige-nous to Ethiopia, Brazil, India, Vietnam, Mexico, Nepal Guatemala, Indonesia, andSri Lanka.

2. Chemical constituents

The main constituents of coffee are caffeine, tannin, fixed oil, carbohydrates,and proteins. It contains 2–3% caffeine, 3–5% tannins, 13% proteins, and 10–15%fixed oils. In the seeds, caffeine is present as a salt of chlorogenic acid (CGA). Also itcontains oil and wax [2].

The following sections will be discussed in detail after acceptance of this shortproposal:

1

• This article will deal on the types of carbohydrate, protein, lipids, and otherchemical constituents in detail.

• This article will review on various analytical methods for the estimation ofconstituents present in coffee.

Coffee is often used as antioxidants, but more importantly coffee is a goodsource of chromium and magnesium that assist in controlling blood sugar by ensur-ing proper usage of insulin.

The main chemical ingredients in coffee beans are given below:

• Caffeine

• Tannin

• Thiamin

• Xanthine

• Spermidine

• Guaiacol

• Citric acid

• Chlorogenic acid

• Acetaldehyde

• Spermine

• Putrescine

• Scopoletin

The carbohydrate content of green and roasted coffee (Santos) was identifiedand measured. Green coffee contained about 6–7% of sucrose as soluble sugars andlow amount of glucose. The soluble sugars of roasted coffee were sucrose, fructose,and glucose. The experiment was also carried out for the isolation of holocellulosefractions of green and roasted coffee.

The holocellulose of green coffee was hydrolyzed by a novel method consistingof anhydrous sulfuric acid and 10% potassium insoluble hydroxide, which waspartially solubilized on roasting and results in the following ratio of sugars:

1 L-arabinose/2D-galactose/2D-glucose/6D-mannose. Out of these sugars, thearabinose was easily acid-hydrolyzed. Other coffee constituent analyzed and deter-mined were caffeine, trigonelline, caffeic acid, chlorogenic acid, isochlorogenicacid, and the 10 amino acids. The free amino acids disappeared in roasting. Ananalytical method was developed for evaluating caffeine on chromatograms [3].

In coffee pulp, condensed tannins are the major phenolic compounds, while inthe seeds, phenolic compounds exist primarily as a family of esters formed betweenhydroxycinnamic acids and quinic acid, collectively recognized as chlorogenic acids(CGA). Green coffee seeds contain up to 14% CGA, which are present in highconcentrations and have a greater influence for determining the quality of coffee

2

Coffee - Production and Research

and play a vital role in the formation of the coffee flavor. The various constituentsalong with components of coffee are shown in Table 1.

3. Carbohydrates

Most of the carbohydrates present, such as cellulose and polysaccharidesconsisting of mannose, galactose, and arabinose, are insoluble.

4. Lipids

The lipid fraction appears to be very stable, and its composition is given below.Linoleic acid is the predominant fatty acid, followed by palmitic acid.Lipid composition.Triacylglycerols.Diterpene esters.Diterpenes.Triterpene esters.Triterpenes (sterols).Unidentified compounds.

5. Acids

The volatile acids include formic acids and acetic acids, while nonvolatile acidsinclude lactic, tartaric, pyruvic, and citric acid. Minor constituents include higherfatty acids and malonic, succinic, glutaric, and malic acids. The degradation prod-ucts of citric acid are itaconic (I), citraconic (II), and mesaconic acids (III), whilefumaric and maleic acids are degraded products of malic acid:

Constituent Components

Soluble carbohydrates Monosaccharides Fructose, glucose, galactose, arabinose (traces)

Oligosaccharides Sucrose, raffinose, stachyose

Polysaccharides Polymers of galactose, mannose, arabinose, glucoseInsoluble polysaccharides

Hemicelluloses Polymers of galactose, arabinose, mannoseCelluloseAcids and phenolsVolatile acids

Nonvolatile aliphatic acids Citric acid, malic acid, quinic acid

Chlorogenic acids Mono-, dicaffeoyl- and feruloylquinic acidLigninLipidsWax

Oil Main fatty acids: N Compounds

Free amino acids Main amino acids: Glu, Asp, Asp-NH2Proteins

Caffeine Traces of theobromine and theophyllineTrigonellineMinerals

Table 1.Constituents along with components of coffee.

3

A Detail Chemistry of Coffee and Its AnalysisDOI: http://dx.doi.org/10.5772/intechopen.91725

Chlorogenic acids are the mainly rich acids of coffee.

6. Trigonelline and nicotinic acid

Green coffee contains trigonelline (N-methylnicotinic acid) up to 0.6% and is50% decomposed during roasting. The degradants include nicotinic acid, pyridine,3-methyl pyridine, nicotinic acid, methyl ester, and other compounds.

7. Aromatic principle

The aroma profile of coffee is composed of the following notes: sweet/caramel-like, earthy, sulfurous/roasty, and smoky/phenolic.

8. Minerals

Potassium is major in coffee ash (1.1%), calcium (0.2%), and magnesium(0.2%). The major anions includes phosphate (0.2%) and sulfate (0.1%), along withtraces of other elements [4].

9. Caffeine

The best known N compound is caffeine (1,3,7-trimethylxanthine) because of itsphysiological effects (stimulation of the central nervous system, increased bloodcirculation, and respiration). It is mildly bitter in taste. 10% of the caffeine andabout 6% of the chlorogenic acid are present in a coffee drink. During roasting, thecaffeine level in beans is decreased. Synthetic caffeine and caffeine obtained by thedecaffeination process are used by the pharmaceutical and soft drink industries. Bymethylation of xanthine, synthetic caffeine is obtained which is obtained from uricacid and formamide. Medicinally, caffeine is used as a CNS stimulant, usuallycombined with another therapeutic agent and in analgesic preparations.

Theobromine acts as diuretic and smooth muscle relaxant, but not routinelyused. Theophylline is used as smooth muscle relaxant and is frequently dispensed insustainable formulations to lower the side effects. It is also available as aminophyl-line (a more soluble preparation containing theophylline with ethylenediamine)and choline theophyllinate (theophylline and choline). The alkaloids may be iso-lated from natural sources or obtained by total or partial synthesis [5].

The purine alkaloids include caffeine, theobromine, and theophylline as shownin Figure 1. They have a limited distribution as alkaloids, but the origins are very

4


close with those of the purine bases like adenine and guanine, fundamental compo-nents of nucleosides, nucleotides, and the nucleic acids. Caffeine is mainly con-sumed in the form of beverages like tea, coffee, and cola and is most widelyconsumed and socially accepted natural stimulants. Theophylline is much moreimportant as a drug compound because of its muscle relaxant properties, utilized inthe relief of bronchial asthma when compared to caffeine, medicinally. The majorconstituent of cocoa and related chocolate products is theobromine.

Out of four nitrogen atoms, two are supplied by glutamine and a third byaspartic acid. The synthesis of the nucleotides AMP and GMP is by way of IMP andXMP, and the purine alkaloids then branch away via XMP. The loss of phosphate viamethylation generates the nucleoside 7-methylxanthosine, which is then releasedfrom the sugar moiety. Furthermore, successive methylation on the nitrogen givescaffeine through theobromine, while a different methylation sequence can result inthe formation of theophylline (Table 2) [6].

AMP = adenosine-50-monophosphate.GMP = guanosine-50-monophosphate.IMP = inosine-50-monophosphate.XMP = xanthosine-50-monophosphate.

Figure 1.Chemistry of the purine derivatives.

5


S.N.

Metho

dExp

erim

ent

Detection

Linearity

rang

eApp

lication

Scientific

outcom

eRef.no.

1UV

spectroscopy

Caffeinesepa

ratedfrom

coffee

usingpa

peran

dTLC

andwas

estimated

usingspectroscopy

Detection

was

done

at272nm

NA

Caffeinefrom

coffee

Goo

dsepa

ration

[7]

2.UV

spectroscopy

Caffeinesepa

ratedfrom

coffee

usingTLC

andwas

estimated

usingspectroscopy

Absorba

ncemeasuredat

274nm

2–120μg

/ml

Caffeinefrom

teapo

wde

rGoo

dsepa

ration

[8]

3.UV

spectroscopy

Metho

dA:sim

ultane

ouseq

uation

metho

dMetho

dB:isosbesticpo

intmetho

d

Formetho

dA:absorba

nce

measuredat

273nm

Formetho

dB:absorba

nce

measuredat

259.5nm

2–32

μg/m

lTab

letcontaining

caffeine

andpa

racetamol

Determinationof

caffeine

inmixture

oftablets

[9]

4.UV

spectroscopy

Dua

lwav

elen

gthmetho

dTwowav

elen

gths

of24

9an

d234nm

wereselected

foran

alysis

LOD

=0.286

LOQ

=0.86

3

3–18

μg/m

lTab

letcontaining

caffeine

andpa

racetamol

Ane

wmetho

dof

determ

inationof

caffeine

[10]

5.HPL

CRP-HPL

CcomprisingC18

column

and24

%metha

nola

smob

ileph

ase

UVde

tector

at272nm

1–40

ppm

Unroasted

coffee

and

roastedcoffee

Unroasted

coffee

containe

d0.89

–2.10

(8samples)

Roasted

coffee

containe

d1.03

–4.21

(11samples)

[11]

6.HPT

LC-U

VSilic

agel6

0F254as

stationa

ryph

asean

dethy

lacetate/m

etha

nol

(27:3)

asmob

ileph

ase

UVde

nsitom

etricremission

at274nm

LOD

=40

ng/zon

eLO

Q=120ng

/zon

e

2–14

μg/zon

eCaffeinein

marke

tedtea

gran

ules

Caffeinein

teasamples

was

foun

dto

be2.14

5%[12]

7HPL

CZorba

xeclip

seXDBcomprising

C8columnas

stationa

ryph

asean

dwater-tetrahy

drofuran

-acetonitrile

asmob

ileph

ase

UVde

tector

at273nm

LOD

=0.07

LOQ

=0.20

0.2–10

0mg/l

Caffeine,

theobrom

ine,

and

theoph

yllin

ein

food

,drinks,a

ndhe

rbalprod

ucts

The

recove

ries

rang

efrom

92.00to

96.8%

[13]

6


S.N.

Metho

dExp

erim

ent

Detection

Linearity

rang

eApp

lication

Scientific

outcom

eRef.no.

8HPL

Can

dbiosen

sor

metho

d

ForHPL

C:S

himad

zuLC

10Afitted

withaC18

columnas

stationa

ryph

asean

daceton

itrile

andwater

(10:90

%)as

mob

ileph

asesetat

aflow

rate

of1mlm

in�1

Forbiosen

sor:

ampe

rometricb

iosensor

comprising

thebiolog

ical

sensingelem

ent,

tran

sduc

er,a

mplification,

and

detector

system

s

UVde

tector

setat

273nm

0.01

–0.1%

w/v

0.01

–0.1%

w/v

Com

mercial

coffee

samples

andcola

drinks

0.03

3–0.07

2%w/v

0.03

0–0.07

6%w/v

[14]

9HPL

CHPL

Cwithsolid

phaseextraction

(SPE

)HPL

Cmod

el:W

aters515,

withUV

detector

(REX,M

odel

pHS-25),

VisiT

M-1

SPEsing

le-sam

ple

processor(Sup

elco)50

mM

KH2P

O4(pH

=2)

Acetonitrile

andmetha

nol(40

:8:2)

was

used

assolven

tas

wellas

mob

ileph

ase

Caffeinewas

extractedfrom

green

tea,

blacktea,

andcoffee

andthen

characterizedby

melting

point,λ

max

(UV/vis),IR

absorption

band

s,Rf(T

LC),an

dRT(H

PLC)

Crude

caffeine

was

purified

bysolid

phaseextraction

10–60

ppm

Caffeinein

tea,

coffee,a

ndsoftdrinks

Crude

blacktea,

greentea,

andcoffee

containe

d7.04

%,

4.88

%,a

nd13.7%

caffeine

,respective

ly,w

hereas

after

purification

blacktea,

green

tea,

andcoffee

containe

d3.34

%,2

.24%

,and

5.20

%pu

recaffeine

[15]

10.

HPL

Can

dUV

UV/visspectrop

hotometer

The

molar

decadicab

sorption

(MDA)coefficien

tsan

dtran

sition

aldipo

lemom

entof

pure

caffeine

inwater

and

dich

lorometha

ne(D

CM)were

obtained

at272an

d274.7nm

MDAwas

foun

dto

be1115

and

1010

m2mol

�1 ,respective

ly,in

water

andDCM

Transitiona

ldipolemom

ents

ofcaffeine

inwater

andin

dich

lorometha

neare10

.40�

10�30

and10

.80�

10�30

Cm,

respective

ly

0.90

–1.10

%for

five

samples

byHPL

C

Caffeinein

coffee

bean

sUV/visspectrop

hotometer:

five

inde

pend

ent

measuremen

tswere

1.1�

0.01

%forBen

chMaji,

1.01

�0.04

%forGed

iyo

Yirga

Che

fe,1

.07�

0.02

%forTep

i,an

d1.19

�0.02

%forGod

ere,

respective

lyHPL

C:m

easuremen

tswere

1.10

%forBen

chMaji,1.10

%forGed

iyoYirga

Che

fe,

1.00

%forGom

maLimu,

and

0.90

%forBesem

a

[16]

7


S.N.

Metho

dExp

erim

ent

Detection

Linearity

rang

eApp

lication

Scientific

outcom

eRef.no.

11HPL

Cwith

DAD

Stationa

ryph

ase:RP-HPL

C(Sph

erisorbODS2

column)

Mob

ileph

ase:0.01

Mph

osph

ate

buffer

ofpH

4

DAD

detector

at26

5nm

LOD

=0.05

μg/m

l0.05

–50

0μg

/ml

The

rmal

degrad

ationof

caffeine

incoffee

ofBrazil

andIvoryCoast

ForBrazil:greencoffee

(g/kg

ofcaffeine

),12.36�

0.10

;roastedcoffee,1

6.12

�0.05

ForIvoryCoast:green

coffee

(g/kgof

caffeine

),20

.83�

0.22;roasted

coffee,

25.55�

0.185

[17]

12HPL

CStationa

ryph

ase:RP-HPL

CC18

Mob

ileph

ase:aceton

itrile/w

ater

(8:92%

)

Detection

atwav

elen

gthof

245nm

.Varieswith

each

sample

Caffeinean

dtheobrom

ine

incoffee,tea,a

ndinstan

tho

tcocoamixes

Instan

ttea:32.4–35.0

mg/cu

pof

caffeine

Tea

bag:30

.2–67.4

mg/cu

p,1.0–

7.8mg/cu

pof

caffeine

Instan

tho

tcocoa:46

.7–

67.6

mg/cu

pof

caffeine

Groun

dcoffee:9

3.0–

163.5mg/cu

pof

caffeine

[18]

13LC

–MS

ForLC

stationa

ryph

ase:Sp

herisorb

S5ODS2,5

μmMob

ileph

ase:form

icacid/

metha

nol

ForMS:ESI

source

with+v

emod

e

LOD

=11.9

ng/m

lLO

Q=39

.6ng

/ml

0.05

–25.00

μg/m

LCaffeine,

trigon

ellin

e,nicotinicacid,a

ndsucrose

incoffee

Caffeineva

lues

rang

edfrom

843.3to

930.9mg/10

0g

coffee

ingreenan

droasted

Arabica

coffee

samples

[19]

14Electroch

emical

metho

dVoltammetricmetho

dwith

CH1760

Delectroche

mical

working

stan

dard

Working

electrod

e:lig

ninmod

ified

glassy

carbon

electrod

eAux

iliaryelectrod

e:platinum

coil

Referen

ceelectrod

e:Ag/Agcl

LOD

=8.37

�10

�7

LOQ

=2.79

�10

�6

6–10

0�

10�6

mol/L

Caffeineconten

tin

Ethiopian

coffee

samples

10.78,

8.78,6

.35,

5.85

mg/g

caffeine

incoffee

[20]

8


S.N.

Metho

dExp

erim

ent

Detection

Linearity

rang

eApp

lication

Scientific

outcom

eRef.no.

15Electroch

emical

metho

dVoltammetricmetho

dW

orking

electrod

e:pe

nciltype

grap

hite

carbon

electrod

eAux

iliaryelectrod

e:platinum

coil

Referen

ceelectrod

e:Ag/Agcl

electrod

e

LOD

=9.2mg/L

0–50

0mg/L

Caffeineleve

lsin

seve

ral

teasamples

Caffeineleve

lsin

seve

raltea

samples

yieldrelative

errorof

1%in

theconc

entrations

[21]

16LC

–MS/MS

ForLC

,station

aryph

ase:

RP-HPL

CC18

Mob

ileph

ase:isocraticmob

ileph

aseconsisting

of0.2%

form

icacid

indistilled

water

andmetha

nol

(80:20

,v/v)

ForMS:spectrom

eter

equipp

edwithan

electrospray

Ionization

mod

eused

togene

rate

positive

[M+H]+ions

LLOQ

=5ng

/ml

5–50

00ng

/ml

Caffeinean

ditsthree

prim

arymetab

olites

inrat

plasma

[22]

17GC-N

PDStationa

ryph

ase:

capilla

ryfusedsilic

acolumn

Mob

ileph

ase:carriergas,he

lium

(1mlm

in�1 )

Detection

was

mad

eby

using

nitrog

enph

osph

orus

detector

LOD

=0.02

μg/m

lLO

Q=0.05

μg/m

l

0.05

–50

0μg

/ml

Caffeinein

teas,c

offees,

andeigh

tbe

verages

Caffeinein:N

escafe

coffee

=24

6.8μg

/ml

Coffeeseed

=26

7.5μg

/ml

Red

Bull=

297.9μg

/ml,while

othe

rsamples

containe

dless

caffeine

[23]

18Infrared

spectroscopy

Fouriertran

sform

infrared

spectroscopy

(FT-IR)metho

dThe

measuremen

twas

done

at1659

cm�1usingaba

selin

eestablishe

dbe

tween1900

and

830cm

�1

LOD

=3mgL�

1

NA

Caffeinein

roastedcoffee

samples

Recov

eryof

allsam

ples

rang

esfrom

94.4

to10

0.1%

[24]

Tab

le2.

The

variousan

alytical

methods

forthedeterm

inationof

caffeine

presentin

coffee.

9


Author details

Hemraj SharmaDepartment of Pharmacy, Shree Medical and Technical College, Bharatpur, Nepal

*Address all correspondence to: [email protected]

©2020TheAuthor(s). Licensee IntechOpen. This chapter is distributed under the termsof theCreativeCommonsAttribution License (http://creativecommons.org/licenses/by/3.0),which permits unrestricted use, distribution, and reproduction in anymedium,provided the original work is properly cited.

10


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Chapter A Detail Chemistry of Coffee and Its Analysis

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