chapter a detail chemistry of coffee and its analysis
TRANSCRIPT
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
Coffee - Production and Research
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
A Detail Chemistry of Coffee and Its AnalysisDOI: http://dx.doi.org/10.5772/intechopen.91725
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
Coffee - Production and Research
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
A Detail Chemistry of Coffee and Its AnalysisDOI: http://dx.doi.org/10.5772/intechopen.91725
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
Coffee - Production and Research
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
A Detail Chemistry of Coffee and Its AnalysisDOI: http://dx.doi.org/10.5772/intechopen.91725
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
Coffee - Production and Research
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A Detail Chemistry of Coffee and Its AnalysisDOI: http://dx.doi.org/10.5772/intechopen.91725
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Coffee - Production and Research