TEA, COFFEE, COCOA AND CHOCOLATE PROCESSINGS

MINISTRY OF EDUCATION AND TRAINING
NONG LAM UNIVERSITY – HO CHI MINH CITY
FACULTY: CHEMICAL ENGINEERING AND FOOD TECHNOLOGY
----

TEA, COFFEE, COCOA AND
CHOCOLATE PROCESSINGS

GROUP 3 - MEMBERS
Võ Nguyễn Thục Trinh
Bùi Thiên Lộc
Nguyễn Thu Hiền
Đỗ Hồng Ánh Mai
Đỗ Thị Yến Ly
Đỗ Thành Trung
January 2022 - Ho Chi Minh city


TABLE OF CONTENT
TABLE OF CONTENT .................................................................................... 1
INTRODUCTION ............................................................................................. 2
PART 1: ANTIOXIDANTS IN TEA, COFFEE AND COCOA AND
THEIR CHANGES DURING PROCESSING ............................................... 4
I. Antioxidants in tea, coffee, and cocoa ...................................................... 4
1. Tea ........................................................................................................... 4
2. Coffee .................................................................................................... 10
3. Cocoa .................................................................................................... 17
II. Changes of antioxidants in tea, coffee, cocoa during processing ....... 19
1. Tea ......................................................................................................... 19
2. Coffee .................................................................................................... 23
3. Cocoa .................................................................................................... 27

PART 2: FAT IN COCOA – THEIR CONTRIBUTION TO
CHOCOLATE PROCESSING ...................................................................... 32
I. Fat in cocoa ............................................................................................... 32
II. Contribution of cocoa butter to chocolate processing ........................ 34
III. Some cocoa butter alternatives are used in processing ..................... 35
CONCLUSION ................................................................................................ 39
REFERENCES ................................................................................................ 41

1


INTRODUCTION
Antioxidants are substances that can prevent or slow damage to cells caused by
free radicals, unstable molecules that the body produces as a reaction to environmental
and other pressures. Antioxidants counter the development of free radicals within the
body. They carry out a process called free radical scavenging, which means they come
through the body tissues and consume free radicals. This means that rejuvenating effects
of correctly roasted coffee doesn’t just come from the caffeine that wakes you up when
you’re sleepy. By drinking healthy coffee, tea, or cocoa you are restoring your cells and
protecting them from the damaging (yet hard-to-avoid) effects of daily life.
Tea remains the most consumed drink in the world after water, well ahead of
coffee, beer, wine, and carbonated soft drinks. An accumulated number of population
studies suggests that consumption of green and black tea beverages may bring positive
health effects. High levels of flavonoids in tea can protect cells and tissues from
oxidative damage by scavenging oxygen-free radicals. Chemically, the flavonoids
found in green and black tea are very effective radical scavengers. The tea flavonoids
may therefore be active as antioxidants in the digestive tract or in other tissues after
uptake. A substantial number of human intervention studies with green and black tea
demonstrates a significant increase in plasma antioxidant capacity in humans
approximately 1h after consumption of moderate amounts of tea (1-6 cups/d). There are

initial indications that the enhanced blood antioxidant potential leads to reduced
oxidative damage to macromolecules such as DNA and lipids. Tea flavonoids are potent
antioxidants that are absorbed from the gut after consumption. Tea consumption
consistently leads to a significant increase in the antioxidant capacity of the blood.
Beneficial effects of increased antioxidant capacity in the body may be the reduction of
oxidative damage to important biomolecules.
The seeds of the tropical tree Theobroma cacao L. are used to make cocoa beans.
Because of the high concentration of bioactive chemicals, such as catechins,
epicatechins, and procyanidins, which are antioxidants. Not only in the food industry,
but also in the pharmaceutical and cosmetic industries, they are in high demand. Cocoa
beans have a substantially higher antioxidant content per serving than black tea, green
tea, or red wine, according to Lee et al. (2003). Interest in these cocoa components has
risen in recent years as a result of their potential health benefits. To prevent or delay
cellular damage, cocoa antioxidants can either quench free radicals or chelate transition
metal ions, limiting their ability to form reactive oxygen species. They also have a
number of physiological characteristics that help them avoid diseases. Catechins
(flavan-3-ols) (37 percent), anthocyanins (4 percent), and proanthocyanidins (58
percent) are the three primary categories of antioxidants (polyphenols) found in cocoa
(Theobroma cacao L.) and cocoa products (Wollgast & Anklam, 2000).

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Coffee is very rich in antioxidants — including the hidroxycinnamic acid family
(caffeic, chlorogenic, coumaric, ferulic, and sinapic acids) as well as other biologically
active chemicals having antioxidant potential, such as caffeine, nicotinic acid,
trigonelline, cafestol, and kahweol. During processing, the antioxidant profile of coffee
changes due to the degradation of native antioxidants and the formation of new ones.
Thus, the antioxidant capacity of coffee is related to the presence of both natural
constituents and compounds formed during processing (roasting) (Vignoli et al., 2011).

Low water activity and high temperatures favor the development of Maillard reactions
(MR), and the formation of MR products between proteins and carbohydrates (Borrelli
et al., 2004).
Cocoa nibs contain about 55% butter, which accounts for about 30% of the
finished chocolate. Saturated fatty acids are found at the 1,3-position and oleic acid is
found at the 2-position in cocoa butter triglycerides. Talbot (1999) found that oleic
(34%), stearic (36%), and palmitic acid (27%) fatty acids are present, along with polar
lipids, sterols, and tocopherols, depending on growing conditions and provenance.
Chocolate melts at temperatures ranging from 23 to 37oC due to its basic glyceride
makeup. Form V (β2) of the lipid crystal is the most desirable in chocolate manufacture
and dominates in well-tempered chocolate. Whole cocoa beans are used to make cocoa
butter. The beans are fermented before being dried for use in chocolate production. To
make cocoa nibs, the beans are roasted and separated from their hulls. The cocoa nibs
are ground to make cocoa mass, which becomes liquid at temperatures above the
melting point of cocoa butter and is referred to as cocoa liquor or chocolate liquor. To
separate the cocoa butter from the non-fat cocoa solids, the chocolate liquor is squeezed.
Deodorization of cocoa butter is occasionally done to remove strong or unpleasant
flavors.
Cocoa butter is used in chocolate to keep sugar particles suspended and
lubricated. Although cocoa butter reduces the viscosity of melted chocolate, it has little
flavor of its own and hence does not contribute significantly to the flavor of chocolate.
Cocoa butter has a variety of distinct qualities that make it a highly sought-after fat. For
technological and economic reasons, cocoa butter alternatives such as cocoa butter
equivalents (CBEs), cocoa butter substitutes (CBSs), and cocoa butter replacers (CBRs)
can partially replace cocoa butter in chocolate manufacture.

3


PART 1: ANTIOXIDANTS IN TEA, COFFEE AND

COCOA AND THEIR CHANGES DURING PROCESSING
I. Antioxidants in tea, coffee, and cocoa
1. Tea
Tea, made from the leaves of the Camellia sinensis plant, is one of the world's
most popular beverages. It has been consumed on a daily basis. Nonfermented green
tea, semifermented oolong tea, and fully fermented black tea are the three varieties.
Fresh tea leaves are steamed or pan-fried to prepare green tea, which inactivates
enzymes and inhibits the oxidation of tea polyphenols.
These chemical compounds act as antioxidants, which control the damaging
effects of free radicals in the body. By stealing electrons from DNA, free radicals can
cause mutations that raise LDL cholesterol or change cell membrane traffic, both of
which are damaging to human health. Though green tea is thought to be higher in
polyphenols than black or oolong (red) teas, studies demonstrate that, with the exception
of decaffeinated tea, all plain teas have similar amounts of these compounds, but in
varying quantities. Green tea has the most epigallocatechin-3 gallate, while black tea
contains the most theaflavins; studies have shown that both have health benefits. Herbal
teas contain polyphenols as well, however the amount varies greatly depending on the
plant.
Tea consumption has been linked to a lower risk of chronic illnesses including
cardiovascular disease and cancer in epidemiological studies. There are also laboratory
research that show tea intake has health benefits. The polyphenol chemicals in tea are
thought to be responsible for these benefits. The most abundant polyphenols in green
tea are catechins. Theaflavins and thearubigins, which are generated by the oxidation
and polymerization of catechins during fermentation, are the major colours in black tea.
Despite accounting for up to 60% of the dry weight of black tea extract, the chemistry
of thearubigins remains unknown.

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• Flavonoids
Polyphenols, also known as flavonoids, are most likely one of the factors that
contribute to tea's health benefits. Flavonoids are plant secondary metabolites that
may be separated into six groups depending on the structure and conformation of
the heterocyclic oxygen ring (C ring) of the basic molecule: flavones, flavanones,
isoflavones, flavanols, flavanols, and anthocyanins (Fig. 1). fAvanols and favonols
are the two primary types of favonoids found in tea. Different quantities of tea
samples were extracted with varying solvents for varied durations of time at
different temperatures, resulting in different extraction efficiencies. After acid
hydrolysis, the content of flavonols in green tea leaves ranged from 0.83 to 1.59,
1.79 to 4.05, and 1.56 to 3.31 g kg-1, while the content of flavonols in black tea
leaves ranged from 0.24 to 0.52, 1.04 to 3.03, and 1.72 to 2.31 g kg-1 for myricetin,
quercetin, and kaempferol, respectively.

Figure 1. Basic structure of flavonoids

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• Catechins
Many different types of polyphenols and catechins may be found in
tea. Catechins are the most abundant. Catechins are molecules with a C6-C3-C6
carbon structure and two aromatic rings, A and B, that belong to the flavonoids
group.

Figure 2. The basic structural formulas of tea catechins.

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Seven different types of catechins are contained in the tea plant, as well as traces
of additional catechin derivatives. There are two types of catechins: free catechins and
esterified or galloyl catechins. Catechins may be found in all areas of the tea plant;
about 15–30 percent can be detected in the tea shoots, and the second and third leaves
have high catechin contents. Catechin content is highest in August when the light of the
sun is the strongest.
The synthesis of free catechins declines over time, whereas galloyl catechins rise.
Catechins are abundant in the bud and higher leaves. Details that, Zaprometov
investigated the synthesis of tea catechins. C was found in the four primary catechins
when CO2 was absorbed with the tea leaves for two hours.

Figure 3. The structural formulas of catechins.

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• Polyphenolic catechins in green tea
The polyphenolic catechins which is an antioxidant in green tea (Camellia
sinensis). They are quite abundant. Green tea consumption may reduce the risk of
cardiovascular disease (CVD) and nonalcoholic fatty liver disease (NAFLD)
(NAFLD). In green tea, catechins contain antioxidant and anti-inflammatory
properties, which help to reduce oxidative stress reactions linked to CVD.
Considering the low bioavailability of dietary catechins, the antioxidant effects of
green tea catechins are expected to be mediated by indirect pathways. Green tea is
good anti-inflammatory properties, which are mediated in part by its antioxidant
properties, inhibit nuclear factor kappa B (NFB) activation, and NFB-dependent
pro-inflammatory responses.

Figure 4. Chemical structures of the predominant catechins found in green tea. Green
tea catechins include both catechin and epicatechin forms. Gallated catechins include

epigallocatechin gallate (EGCG), gallocatechin gallate (GCG), epicatechin gallate
(ECG), and catechin gallate (CG). The major non-gallated catechins are epicatechin
(EC), catechin (C), epigallocatechin (EGC), and gallocatechin (GC).

8


• Theaflavins
Theaflavins, which give black tea its vivid red color, have a benzotropolone
skeleton that is generated by the co-oxidation of two catechins, one with a
victrihydroxyphenyl moiety and the other with an orthodihydroxyphenyl structure.
The qualities of black tea, including as color, 'mouthfeel,' and the degree of tea cream
development, are all influenced by theaflavins. Their structures have been
thoroughly investigated. Theaflavin, theaflavin 3-gallate, theaflavin 30 -gallate, and
theaflavin 3,30-digallate (Figure 5) are four primary theaflavins in black tea that are
formed by oxidative coupling between EC and EGC, EC and EGCG, ECG and EGC,
ECG, and EGCG, respectively.

Figure 5. Structures of major theaflavins in tea.

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2. Coffee
Coffee is a popular beverage that has long been used as a meal complement as
well as a hedonistic and psychostimulant. It is believed that 80 percent of the adult
population in the world consumes coffee beverages (Sridevi et al., 2011). Although
coffee has been widely used for centuries due to its pleasant aroma, modern
epidemiological research has found that regular coffee consumption provides a number
of health benefits due to its biochemical composition. Coffee contains vitamins such as

B3 and B12. Coffee also contains additional beneficial chemical elements such as
antioxidants, fiber, and melanoidins, among others. Coffee is high in antioxidants from
the hidroxycinnamic acid family (caffeic, chlorogenic, coumaric, ferulic, and sinapic
acids) as well as other biologically active chemicals having antioxidant potential, such
as caffeine, nicotinic acid, trigonelline, cafestol, and kahweol as presented in table 1
(Sridevi et al., 2011).
Table 1. The main antioxidants in Arabica coffee and Coffea canephora (Robusta coffee).

Antioxidant activity of coffee is related to chlorogenic, ferulic, caffeic, and ncoumaric acids contained in it.

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• Chlorogenic acids (CGAs)
Chlorogenic acids (CGAs) are a family of esters that are structural analogs of
quinic acid (QA) carrying one or more cinnamate derivatives such as caffeic, ferulic,
and p-coumaric acids (Narita & Inouye, 2015).
CGA's biological qualities have recently been described, in addition to its
antioxidant and anti-inflammatory activities. CGA is thought to have a key role in
glucose and lipid metabolism, as well as related illnesses such as diabetes,
cardiovascular disease (CVD), obesity, cancer, and hepatic steatosis. CGA's antidiabetic, anti-carcinogenic, anti-inflammatory, and anti-obesity properties may give
a non-pharmacological and non-invasive strategy to treating or preventing several
chronic conditions. Certain plant species generate chlorogenic acid (CGA), a
physiologically active dietary polyphenol that is a primary component of coffee.
CGA consumption has been linked to a reduction in the risk of a variety of diseases
in current fundamental and clinical research investigations.

Figure 6. Chemical structures of CGAs from green coffee beans. (A) Structures of key
groups of and quinic acid found in CGAs from green coffee beans.

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The content of CGAs in green coffee beans for human consumption (C. arabica
and C. canephora) is in the range of 3.40–14.4% w/w dry matter, though that in some
Coffea species is <1% w/w dry matter. Eighty-two CGAs were detected in green coffee
beans. The contents of total CGAs, caffeoylquinic acids, feruloylquinic acids, and
diferuloylquinic acids in commercial roasted coffee beans are 2.66%, 2.26%, 0.21%,
and 0.19% w/w dry matter as showed in table 3, respectively. The content of CGAs in
commercial instant coffee is CGA in the range of 3.61–10.73% w/w dry matter (instant
coffee powder).
Table 2. Contents of Chlorogenic Acids (CGAs) of Green Coffee Beans (Coffea arabica
and Coffea canephora).

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Table 3. Contents of Chlorogenic Acids (CGAs) of Roasted Coffee Beans (Coffea
arabica and Coffea canephora).

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• Caffeine
Caffeine is an alkaloid found in different levels in brewed coffees and is
well recognized for its effects on mental alertness, information processing speed,
wakefulness, restlessness, fatigue decrease, and sleep deferral. It's also accessible
as a tablet and is widely utilized in pharmaceuticals and beverages. Caffeine level
in coffee brews varies depending on bean variety, brewing strength, and roasting
procedure. In general, the caffeine concentration of the same variety of coffee bean

brewed in the same way can range from 130 to 282 mg/240 mL, with Arabica
brewed coffee containing between 36 and 112 mg caffeine/100 mL and Robusta
brewed coffee containing between 56 and 203 mg/100 mL(Komes & Bušić, 2014).

Figure 7. Chemical structure of caffeine (1, 3, 7-trimethylxanthine).
Caffeine and its catabolic products theobromine and xanthine exhibit both
antioxidant and pro-oxidant properties. Therefore, caffeine and its metabolites may
also contribute to the overall antioxidant and chemopreventive properties of
caffeine-bearing beverages (Azam et al., 2003). There is conflicting evidence
regarding the contribution of caffeine to the antioxidant capacity of coffee brews.
While Brezová et al. (2009) found a high antioxidant capacity of caffeic acid but not
of caffeine, Vignoli et al. (2011) reported high correlations between antioxidant
capacity of coffee brews and caffeine. Similarly, López-Galilea et al. (2007)
reported a significant correlation between caffeine content and antioxidant capacity
obtained by DPPH (r=0.83) and redox potential (r=0.84), depending on the brewing
technique. In addition, Santini et al. (2011) also observed a direct relation between
caffeine content of Arabica coffee brews and corresponding antioxidant capacity.

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• Trigonelline
Trigonelline is a bitter alkaloid in coffee which serves to produce important
aroma compounds. In terms of concentration trigonelline is higher for arabica than
robusta and ranges from about 0.6-1.3% and 0.3-0.9%, respectively. Trigonelline
(1-methylpyridinium-3-carboxylate) is one of the major components of coffee
beans, representing ∼2% of the dry weight (Mazzafera, 1991). It is also one of the
candidate compounds responsible for the bitter taste of the coffee brew. Trigonelline
is thermally unstable and during roasting it is converted to nicotinic acid and other
nitrogenous compounds that contribute to flavor (Mazzafera, 1991). During

germination of coffee seeds, limited content of trigonelline is catabolized and used
as a substrate for the synthesis of nitrogen containing compounds (Shimizu and
Mazzafera, 2000). Trigonelline, demethylated to nicotinic acid, supplies 1–3mg of
nicotinic acid/240ml of brewed coffee (Higdon and Frei, 2006; Stadler et al., 2002).

Figure 8. Chemical structure of trigonelline.

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• Tocopherols
Tocopherols are a group of four lipid-soluble amphipathic molecules (α-,
β-, γ-, δ-) that are exclusively synthesized by photosynthetic organisms.
Collectively, they are an essential component of vitamin E (Gilliland et al.,
2006), which is known to be the most effective natural lipid-soluble antioxidant,
protecting cell membranes from peroxyl radicals and mutagenic nitrogen oxide
species (Gliszczyńka-Świgło and Sikorska, 2004). The presence of tocopherols
in coffee oil was reported for the first time by Folstar et al. (1977).
Among tocopherols, two main tocopherols (α- and β-) were identified in
Arabica and Robusta coffee beans, both green and roasted (Alves et al., 2010).
Ogawa et al. (1989) reported vitamin E mean content in coffee brew of
7±3μg/100ml. The content of α-tocopherol in roasted coffees ranged between
7.55 μg/g and 33.54 μg/g, whereas in green coffees it was between 2.02 μg/g and
16.76 μg/g. In the case of β- and γ-tocopherols, remarkable differences between
green and roasted samples were observed, with their contents being higher in
roasted coffees. Thus, the mean values of β-tocopherol were evaluated to be
47.12μg/g and 106.60μg/g for green and roasted coffees, respectively. In the case
of γ-tocopherol, its content varied between 2.63μg/g in green samples and
70.99μg/g in roasted coffee beans (Gonzales et al., 2001). The increase in
tocopherol content during the roasting process has been already described for

some oilseeds (Yen, 1990), and was explained as the result of liberation of the
combined tocopherols during the roasting process.
Recently, the usefulness of tocopherol content and profile as a marker of
coffee adulteration with corn was also described by Jham et al. (2007)

Figure 9. Chemical structure of tocopherol.

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3. Cocoa
Cocoa beans are the seeds of the tropical tree Theobroma cacao L. Because of
the high concentration of bioactive compounds, including antioxidants - catechins,
epicatechin, and procyanidins. They're in high demand not only in the food sector, but
also in the pharmaceutical and cosmetic industries. According to Lee et al. (2003) cocoa
beans contain much higher antioxidant capacity per serving than black tea, green tea
and red wine. Because of their possible beneficial impacts on human health, interest in
these cocoa components has soared in recent years. Cocoa antioxidants can either
quench free radicals or chelate transition metal ions, reducing their ability to produce
reactive oxygen species, to prevent or delay cellular damage. They also have a variety
of physiological features that protect them from diseases such as coronary heart disease,
cancer, and neurological disorders. Antioxidants (polyphenols) in cocoa (Theobroma
cacao L.) and cocoa products can be classified into three main groups: catechins (flavan3-ols) (37%), anthocyanins (4%), and proanthocyanidins (58%) (Wollgast & Anklam,
2000).
Forsyth reported that cocoa bean contains four types of catechins, of which (-)epicatechin constitutes about 92%. The primary catechin is (−)-epicatechin, up to 35%
of total polyphenols and from 34.65 to 43.27 mg/g of defatted freshly harvested Criollo
and Forastero beans. Less abundant is (+)-catechin with only traces of (+)-gallocatechin
and (−)-epigallocatechin. Nazaruddin et al. (2001) reported total polyphenols ranged
from 45 to 52 mg/g in cocoa liquor, 34 to 60 in beans and 20 to 62 in powder: (−)epicatechin contents were 2.53, 4.61 and 3.81 mg/g, respectively. The contents of (-)epicatechin was 2.23 ± 0.6 mg/g. These data are just used for references and cannot be
directly compared with the data found in other publications, due to differences in

methods of phenolic extraction, data from our study fall within the range found in the
literature.
The anthocyanin fraction is dominated by cyanidin-3-α-l-arabinoside and
cyanidin-3- β-d-galactoside. Total procyanidins accounted for a mean percentage of
63.71% of the total phenolics. Procyanidins are mostly flavan-3,4-diols and are four to
eight or four to six bound to form dimers, trimers, or oligomers with epicatechin as the
main extension subunit. The contents of dimers epicatechin-(4β→8)-catechin
(procyanidin B1) and (epicatechin-(4β→8)-epicatechin) procyanidin B2 were 0.28 ±
0.03 mg/g and 0.63 ± 0.03 mg/g, respectively. Procyanidins are converted to largely
insoluble red-brown material resulting in the characteristic color of chocolate during
fermentation and roasting.

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Figure 10. Structures the catechin and epicatechin enantiomers.

Figure 11. Structures of procyanidin dimer and trimer in cocoa.
Polyphenol oxidase promotes oxidative browning to give the characteristic
chocolate brown color of well-fermented Forastero beans.

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II. Changes of antioxidants in tea, coffee and cocoa during
processing
1. Tea
Identification of catechins, theaflavins, and flavonols in green and black tea
samples.
Rolling and Drying

Catechins, theaflavins, and flavonols demonstrated different changes in
composition and content in each processing step of green and black teas (Table 4).
Table 4. Mass spectrometric data and contents (mg/100 g dry weight) of individual
flavonoids in each processing step of green and black tea (Camellia sinensis) leaves.

The total flavonoid content of green tea was significantly increased after the
roasting step. Specifically, major catechins, EGCG and ECG, reached the highest level
on the final product, and their contents (mg/100 g DW) increased approximately
twofold over fresh leaves. Theaflavins were present in the fresh leaves but vanished
after roasting. Heating processing (250–300 °C) was considered to cause the increase
or decrease of certain components through drying or hydrolysis under water-free
conditions and was one of the important factors that affect the chemical composition of
tea. The catechin content of green tea liquor decreased as the infusion temperature
increased. However, because the flavonol content was slightly increased after roasting,
19


it was difficult to conclude that the significant increase in catechin was entirely due to
water evaporation of the fresh leaf. Based on these findings, the roasting step is also
expected to reduce catechin content loss by inactivating the polyphenol oxidase (PPO)
enzyme, which leads to catechin degradation in fresh leaf.
The contents of catechins and flavonols, on the other hand, were significantly
reduced by the rolling step and then increased again after drying steps in green tea. The
loss of ECG and EGCG contents during leaf processing was reduced as the rolling time
was reduced. The flavonols tended to reach their maximum level over the three drying
steps, but there were no significant differences in mono- and tri-glycosides, as well as
total content, until the final product was completed over the second and third drying
steps (Fig. 12b). In particular, as a major class, kaempferol mono- and tri-glycosides
(peak 12, 15, 16, and 18) had the highest contents, while quercetin mono- and triglycosides (peak 8, 9, 13, and 14) had slightly lower contents than the previous step on
the final product (Table 4). Roasting and drying were found to be the most important

factors in changing individual catechin and flavonol contents in green tea processing.

Figure 12. Distribution of flavonoids by tea leaf processing. a Variation of theaflavin
contents (mg/100 g dry weight, DW) by acylated forms (aglycone, mono- and
di); b variation of flavonol contents (mg/100 g DW) by glycosidic forms (aglycone,
mono-, di-, and tri-).

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Fermentation
Fermentation is the critical step in the production of black tea leaf that results in
the greatest change in flavonoid composition and content. The majority of studies have
looked at flavonoid changes in simple fermented teas such as black, oolong, and Pu'er
teas. The chromatogram in Figure 13a showed that catechins were almost certainly
converted to theaflavins during the fermentation step of black tea. Fermentation, in
general, is one of the most affected methods of changing the ingredients in agro-food
processing. Catechins, on the other hand, induce a condensation reaction after oxidation
by PPO enzyme to form theaflavins, thearubigins, and proanthocyanidins with high
molecular weight during black tea processing, and the higher concentration of
theaflavins could be due to this chemical phenomenon (Fig. 13c). The catechin content
(mg/100 g DW) increased slightly during withering and then decreased significantly
during the rolling and fermentation steps. When it became the final product after drying,
the reduced content of individual catechins was roughly doubled again (Table 4). The
total theaflavin content (mg/100 g DW) increased significantly throughout the entire
black tea processing sequence: withering → rolling → fermentation → first drying →
second drying → final product. In Figs. 13c and 1a, theaflavin 3,3′-di-O-gallate (305.6)
and theaflavin 3-O-gallate (168.4), which were advanced with gallic acid in the
biosynthetic pathway, showed the greatest increases of 4.5- and sixfold as predominant
compounds, respectively, when compared to fresh leaf.

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Figure 13. UPLC chromatograms of flavonoids in final green and black tea products. a
Wavelengths at 280 nm for catechins and theaflavins; b 350 nm for flavonols; c
biosynthetic pathway of theaflavin derivatives.

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Significant differences in flavonol content of black tea were found between fresh
leaf and final product, but only a 23% reduction was observed when compared to green
tea. In summary, there was no significant difference in kaempferol and quercetin
glycosides between fresh leaf and final product in Table 4. Myricetin glycosides, on the
other hand, displayed distinct patterns depending on their glycosidic form. Surprisingly,
the tri-glycosides of myricetin were completely eliminated after fermentation, and the
mono-glycosides of the final product were reduced by more than 50% when compared
to fresh leaf.
Chemical compounds such as EGCG, ECG, and theaflavins may be evaluated as
a potential quality indicator for grading green and black tea infusions. Green and black
tea catechins and flavonols are normally reduced by rolling step. To investigate the
minimum loss of catechins and flavonols, detailed rolling conditions are required.
Theaflavins, which were only found in black tea processing, could be used as a healthpromoting compound in high-quality black tea.
Individual flavonol contents varied depending on their aglycone type and
glycosylated form during leaf processing. In particular, the roasting step generally
increased catechin content, including EGCG and ECG in green tea, but catechins were
significantly reduced in black tea due to oxidation and conversion to theaflavins after
the fermentation step. The drying multi-steps were also discovered to be a factor that
positively influences the increase of flavonoids in tea processing.

2. Coffee
Recent research has found that coffee ingredients such as caffeine, phenolic
compounds, chlorogenic acids, and hydroxycinnamic acids, as well as chemicals
generated from Maillard reactions such as melanoidins, have antioxidant qualities.
According to Svilaas coffee-based drinks contribute to 64% of the total antioxidant
intake, followed by fruits, berries, tea, wines, cereals and vegetables (Svilaas et al.
2004). Green coffee beans include phenolic chemicals such as chlorogenic acid, caffeic
acid, ferulic acid, and p-coumaric acid. In the human diet, coffee is the most abundant
source of chlorogenic acid. On the basis of 10 g of coffee per cup of brew, a cup contains
15−325 mg of chlorogenic acids; daily intake of coffee drinkers is 0.5−1.0 g, whereas
coffee abstainers typically ingest < 100 mg/day (Richelle et al. 2001; Castillo et al.
2002). Roasting has a significant impact on the composition of coffee. The roasting
process is divided into two stages. The first process is drying (bean temperature less
than 160°C), and the second phase is roasting (bean temperature between 160 and
260°C). At 190°C, pyrolytic processes begin, generating oxidation, reduction,
hydrolysis, polymerisation, decarboxylation, and many other chemical changes,
resultintog to the synthesis of chemicals necessary for the sensory characteristics of the
coffee, among other things. Moisture loss and chemical reactions cause significant
changes in color, volume, mass, shape, bean pop, pH, and density, as well as the
production of volatile components and CO2, a portion of which escapes, and the
remainder is kept in the cells of the beans. Following this second phase, the beans must
be swiftly chilled to halt the reactions (using water or air as a cooling agent) and to
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avoid an over-roasted result. During the process, several parameters can be used as
indicators to determine the degree of roasting (aroma, flavour, colour, bean’s
temperature, pH, chemical composition, bean pop, mass loss, gas composition and
volume) (Hernandez et al. 2007). Although compounds with antioxidant properties are

lost during roasting of coffee beans, the overall antioxidant properties of coffee brews
can be maintained, or even enhanced, by the development of compounds possessing
antioxidant activity, including Maillard reaction products (Castillo et al. 2002). A major
contributor to the antioxidant activity was identified as N-methylpyridinium. The levels
of 1-methylpyridinium in roasted and ground coffee are positively correlated to the
degree of roasting (Stadler et al. 2002a, b). Methylpyridinium is not found in raw coffee
beans; nevertheless, it is generated during the roasting process from its chemical
precursor, trigonelline, which is found in raw coffee beans. Trigonelline is the second
most abundant alkaloid in green coffee and reaches levels in Coffea arabica and Coffea
canephora var. robusta from 7.9 to 10.6 g/kg and from 6.6 to 6.8 g/kg, respectively
(Stennert & Maier 1994).
Coffee is said to be the most significant natural antioxidant source in the diet.
The recent studies suggest that the most important antioxidant in coffee is
methylpyridinium which is formed by degradation of trigonelline during the roasting
process (Stennert & Maier 1994; Stadler et al. 2002a, b). Several parameters were
monitored during the roasting and subsequent storage of the Robusta coffee, including
trigonelline, chlorogenic acid, total polyphenols concentration, and total antioxidant
capacity. The results are given in Figure 1 and in Table 5, there are summarised the
changes in the water content, the water activity, and colour during the roasting and
storage of coffee.
Table 5. The changes of moisture, water activity and Cielab scale parameters during
the roasting of coffee beans.

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