catechins in foods

7/17/2019 Catechins in Foods

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Novel uses of

catechins in foods

Yusuf Yilmaz&

Department of Food Engineering, Pamukkale Uni-versity, Camlık 20017, Denizli, Turkey (Tel.:C90

258 212 5532; fax: C90 258 212 5538.; e-mail:[email protected])

Catechins are flavanols present in a variety of foods such

as wine, tea, fruits and chocolate. Catechin, epicatechin

and gallates of epicatechin are major catechins with

dietary importance for human health. In recent years,

catechins have been used as natural antioxidant in oils

and fats against lipid oxidation, supplement for animal

feeds both to improve animal health and to protect

animal products, an antimicrobial agent in foodstuffs and

a health functional ingredient in various foods and dietary

supplements. This review outlines the novel uses of catechins in foods.

IntroductionFlavonoids are secondary metabolites of plants, which

are derived from the condensation reaction of a cinnamic

acid with three malonyl-CoA groups (Bloor, 2001). They

are generally categorized as phenolics or polyphenols

because of their chemical structure (Fig. 1). Over 4000

flavonoids have been identified. Although flavonoids are

responsible for the color of fruits and vegetables,

colorless flavonoids are also present in nature. Theclassification of flavonoids varies based on the level of

oxidation in the structure of ring (14 classes according to

Seigler, 1995); however, major dietary flavonoids are

often classified under six groups (Peterson & Dwyer,

1998) shown in Table 1. Catechins belong to the group

of flavonoids called flavan-3-ols.

Some of the polyphenolics are known to have

potential antioxidant activities. Many herbal medicines

used to treat vascular, viral, gastrointestinal, microbial

and inflammatory diseases may contain plant polyphenols

(Haslam, 1989). Their medicinal properties make them a

potential group of compounds beneficial to human health.While the average daily dietary intake of flavonoids in

the US may be only a few 100 mg, approximately half of

the daily flavonol and flavone intake in the Netherlands

comes from tea (Hollman & Katan, 1999). Dietary intake

of flavonoids is usually underestimated because of the

difficulty in measuring the amount of all flavonoids

present in the consumed foods. Peterson & Dwyer (1998)

reported that daily intake of flavonoids could range from

23 to 1000 mg/day. Chocolate contributes 20% of thedaily catechin intake in the Dutch population, and tea

contributes 55% (Arts, Hollman, & Kromhout, 1999).

Mediterranean diets, which are rich in wines and fresh

fruits and vegetables, were found high in catechins

(Auger et al., 2004). In Mediterranean diets, Auger et al.,

(2004) estimated the maximum daily intake of catechins

and procyanidins around 100 mg for a person who

consumes red wine moderately.

Health beneficial properties of catechins have been

reported widely in the literature (see Higdon and Frei,

2003 for more information). In recent years, catechins

have been increasingly used as a natural ingredient in

foodstuffs and feedstuffs for various purposes. The aim of

this paper is to review the novel uses of catechins in foods

or feeds.

Major catechins in foodsCatechins are flavanols, which are also called proantho-

cyanidins or flavan-3-ols. This group of flavonoids includes

major catechins such as catechin, epicatechin, epicatechin

gallate (ECG), and epigallocatechin-3-gallate (EGCG)

(Fig. 2). Catechins are naturally present in fruits, vegetables,

tea and wine. Red wine, green, black and oolong teas, fruits

like plum, apples, peach, strawberry and cherry, and beans

and grains like broad bean, lentil and cocoa are rich in

catechins. It is also a monomer that forms dimeric, trimeric

and oligomeric proanthocyanidins of grape berries includ-

ing their skins and seeds.

Tea, aqueous infusion of dried leaves of the plant

Camellia sinensis L. (family Theaceae), contains catechins

as well as caffeine, amino acids, carbohydrates, protein,

chlorophyll, volatile compounds, fluoride, minerals, and

other undefined compounds (Graham, 1992). Total catechin

contents of green and black tea are 420 and 250 mg/L,

respectively (Auger et al., 2004). Catechins degrade during

fermentation process of black tea, and its degradationdepends on the fermentation temperature (Obanda, Owuor,

0924-2244/$ - see front matter q 2005 Published by Elsevier Ltd.doi:10.1016/j.tifs.2005.10.005

Trends in Food Science & Technology 17 (2006) 64–71

Review



& Mang’oka, 2001). Peterson et al. (2005) calculated that

fermentation of green tea significantly lowers the total

catechin content of tea from about 14 to 4% (w/w dry basis).

Catechins constitute 60–90% of total flavonoids in green tea

while 6–24% of total flavonoids are catechins in black tea

(Higdon & Frei, 2003). Tea waste can be also considered as

a valuable material due to its left over bioactivecomponents, including catechin, epicatechin, epigallocate-

chin (EGC), EGCG and ECG (Nwuha, Nakajima, Tong, &

Ichikawa, 1999). Chocolate is also rich in catechins and

procyanidins (Wollgast & Anklam, 2000a,b), and the

amount of catechins in chocolate could be four times higher

than tea (Arts et al., 1999).

CatechinCatechin, a monomeric flavanol (Fig. 2), is reported to

have hydroxyl (Moini, Guo, & Packer, 2002), peroxyl

(Scott, Butler, Halliwell, & Aruoma, 1993), superoxide

(Bors & Michel, 1999) and DPPH (1,1-diphenyl-2-picryl-

hydrazyl) (Fukumoto & Mazza, 2000) radical scavenging

activities. Moreover, it can chelate iron (Morel et al., 1993).

Nakao, Takio, and Ono (1998) found that ECG, epicatechin

and catechin have a peroxyl radical scavenging activity ten

times higher than L-ascorbate and b-carotene when tested on

bacteria. Nanjo et al. (1996) reported that DPPH radical

scavenging activity of catechin and epicatechin is less than

EGC, ECG, and EGCG.

EpicatechinEpicatechin is another monomeric flavanol found

naturally in vegetables, fruits, wine and tea. Epicatechin

along with catechin are present in apples, and their

concentration depends on fruit development and ripening

(Awad, Jager, van der Plas, & van der Krol, 2001).

Epicatechin has an ortho-dihydroxyl group in the B-ring

at carbons 3 0 and 4 0 and a hydroxyl group at carbon 3 on the

C-ring (Fig. 2). Epicatechin is able to scavenge hydroxyl

radicals (Moini et al., 2002), peroxyl radicals (Liu, Ma,

Zhou, Yang, & Liu, 2000), superoxide radicals (Bors &

Michel, 1999), and DPPH radicals (Fukumoto & Mazza,

2000). Peroxyl radical scavenging activity of epicatechin

could be ten times higher than L-ascorbate or b-carotene

(Nakao et al., 1998).

Gallates of epicatechinBlack tea contains mainly gallates of epicatechin. In

black tea, green tea and oolong tea, epicatechin, EGC,

EGCG and ECG are present, but not catechin (Khokhar,

Venema, Hollman, Dekker, & Jonge, 1997). ECG and

EGCG are considered the main catechins found in black tea

(Obanda et al., 2001).

EGC differs from epicatechin in that it has a trihydroxyl

group at carbons 3 0, 4 0, and 5 0 on the B-ring (Fig. 2). ECG

differs from epicatechin in its gallate moiety esterified at

Fig. 1. Basic monomeric structure of flavonoids.

Table 1. Major dietary flavonoids and examples

Flavonoid Examples

Anthocyanidins Delphinidin, cyanidin, petunidin, peonidin, and malvidinFlavonols Quercetin, kaempferol, and quercetagetinFlavanols Catechin, epicatechin, epicatechin gallate, and epigallocatechin-3-gallateIsoflavonoids Isoflavones (e.g. genistein, diadzein, formononetin, and biochanin A), and coumestans (e.g. coumestrol)

Flavones Rutin, apigenin, luteolein, and chrysinFlavonones Myricetin, hesperidin, naringin, and naringenin

Fig. 2. Chemical structure of major catechins found in tea.

Y. Yilmaz / Trends in Food Science & Technology 17 (2006) 64–71 65



carbon 3 of the C-ring. However, EGCG has both

trihydroxyl groups at carbons 3 0, 4 0, and 5 0 on the B-ring

and a gallate moiety esterified at carbon 3 on the C-ring.

EGCG is the most abundant catechin in the leaves of green,

oolong, and black teas (Graham, 1992). EGCG contents of

green and oolong teas range typically from 127 to 550 mg/ L, while black teas may contain up to 300 mg/L (Balentine

& Paetau-Robinson, 2000).

Novel uses of catechins in foodsAntioxidant in oils and fats

The major sources of catechins used in foods come from

mostly different types of tea since it is highly available

throughout the world and a relatively inexpensive source of

catechins with a plant origin. In the literature, there are

numerous studies on the in vitro antioxidative activity of tea

catechins against various radicals such as hydroxyl, super-oxide, peroxyl and DPPH (Atoui, Mansouri, Boskou, &

Kefalas, 2005; Tang, Kerry, Sheehan, & Buckley, 2002).

Radical scavenging activities of major tea catechins like

catechin, epicatechin and gallates of epicatechin have been

presented in the previous section of this paper. This section

focuses on the exploitation of tea catechins’ antioxidant

activity in food matrices such as meats, poultries, fish and

vegetable oils.

Red meats and poultry are usually susceptible to lipid

oxidation due to their high fat content. Fat contents of

meats depend on several factors such as the type, gender,

and age of animals, and the type of animal tissue. Thereare a few studies on the use of tea catechins, natural

antioxidants, to prolong the shelf life of different meat

types by inhibiting lipid oxidation. In a study by Tang,

Kerry, Sheehan, Buckley, and Morrissey (2001a), the

addition of tea catechins at a level of 300 mg/kg was

shown to inhibit lipid oxidation significantly in red meat

and poultry patties; however, concentrations of tea

catechins higher than 300 mg/kg were needed for the

inhibition of lipid oxidation in samples with high levels of

highly unsaturated lipids like fish. McCarthy, Kerry,

Kerry, Lynch, and Buckley (2001a,b) indicated that tea

catechins along with rosemary and sage at levels less than

0.5% could be used as natural antioxidants to reduce lipid

oxidation in raw and cooked pork patties produced from

frozen pork meat. Tea catechins were found the most

effective antioxidant against lipid oxidation of cooked

pork patties among ginseng, mustard, rosemary, sage,

butylated hydroxyanisole/butylated hydroxytoluene (BHA/

BHT) and vitamin E. In a recent study, Mitsumoto,

O’Grady, Kerry, and Buckley (2005) successfully used tea

catechins (200–400 ppm) to inhibit lipid oxidation in

cooked or raw beef patties. However, discoloration in

cooked beef and chicken patties was also observed at

these concentrations of tea catechins. The authors reported

that inhibitory effect of tea catechins against lipidoxidation in raw beef was higher than sodium ascorbate

(vitamin C) acid at the same concentration. Direct

addition of 1000 ppm tea catechins to M. longissimus

dorsi steaks was found to improve the color and lipid

stability of beef patties significantly (Kerry, 2005).

Fish is even more susceptible to lipid oxidation than

red meats and poultry because fats in fish tissues arecomposed of highly unsaturated fatty acids like arachi-

donic acid. The blue sprat, small herring processed like a

sardine, is mostly consumed locally because it deteriorates

very rapidly after catching. Using hot water extracts of

different teas including green, oolong and black teas, Seto,

Lin, Endo, and Fujimoto (2005) found that extracts of teas

inhibited the oxidation of blue sprat tissues, and this

inhibition was positively correlated with the total

catechins contents of tea extracts. They also found that

green and oolong teas were effective for the suppression

of lipid peroxidation in dark meat and skin of blue sprat.

O’Sullivan, Mayr, Shaw, Murphy, and Kerry (2005)reported that tea catechins inhibited the lipid oxidation

of cod liver oil and white Pollack liver oil better than

black clove oil, white clove oil, mustard, carvacol or

vitamin E. Studying the antioxidant activity of ground

green tea, tea extracts and pure tea catechins in a white

muscle of mackerel cooked at 75 8C and stored at 4 8C for

a week, He and Shahidi (1997) reported that ground green

tea, tea extracts and tea catechins such as epicatechin,

EGC, ECG, and EGCG can be used as an antioxidative

agent in a fish meat model system instead of artificial

antioxidants such as a-tocopherol, BHT, BHA, or tertiary

butyl hydroquinone (TBHQ).

Lipid oxidation of animal fats is likely to occur during

extended periods of storage at refrigeration temperatures.

Tea catechins, natural compounds with antioxidant

activity, have a potential to be utilized in muscle foods

for the inhibition of lipid oxidation during storage.

Investigating the effect of tea catechins on the lipid

oxidation in red meat, poultry and fish muscles stored at

4 8C for 10 days, Tang, Sheehan, Buckley, Morrissey,

and Kerry (2001) found significant reduction in lipid

oxidation when 300 ppm tea catechins were added to

muscle meats. Moreover, the antioxidative activity of tea

catechins was higher than that of a-tocopherol at the

same concentration. In a study, Shahidi and Alexander(1998) found that green tea catechins such as epicatechin,

EGC, ECG and EGCG (200 ppm) inhibited the oxidation

of meat lipids better than a-tocopherol, and gallates

of catechins were more effective than monomer

epicatechin in controlling lipid oxidation in a meat

model system.

Tea catechins are able to scavenge DPPH radicals

(Atoui et al., 2005; Tang, Kerry, Sheehan, Buckley, &

Morrissey, 2001b) and chelate Fe2C

(Tang et al., 2002),

i.e. they are potential antioxidants. Catechin, one of the

major tea catechins, increases the stability of peanut oil

most significantly compared to rosemary, tocopherol,phospholipids and ascorbyl palmitate (Chu & Hsu,

Y. Yilmaz / Trends in Food Science & Technology 17 (2006) 64–7166



1999). Jasmine tea extracts containing epicatechin, EGCG,

EGC, and ECG can be a better antioxidant than BHT in

canola oil (Chen & Chan, 1996). In an oil matrix, stability

of catechins could be problematic; however, catechins

from tea extracts were found thermally more stable than

BHT (Chen & Chan, 1996). Studying the antioxidantactivity of aqueous green tea extracts on ‘refined,

bleached, and deodorized seal blubber oil and menhaden

oil’, Wanasundara and Shahidi (1998) found that

chlorophyll in green tea extracts was responsible for

pro-oxidative activity on these oil samples because

dechlorophyllized tea extracts (O200 ppm) in both oils

exhibited antioxidant activity. In conclusion, tea catechins

could be used as a novel potential ingredient in vegetable

oils and food products of oils for the inhibition of

oxidation in lipids; however, precaution is needed because

of the presence of pro-oxidative constituents of tea.

Further investigations should focus on the consumeracceptability of oils and oil products with catechins.

Studies on the antimutagenic activity of tea poly-

phenols are likely to accelerate the utilization of tea

extracts in foods as a functional ingredient. In a study by

Gupta, Chaudhuri, Seth, Ganguly, and Giri (2002), black

tea and its phenolics theaflavins and thearubigins were

shown to have significant in vitro anti-mutagenic activity.

It could be speculated that antimutagenic activities of tea

extracts together with their antioxidant activities are likely

to encourage the exploitation of tea catechins as a

functional ingredient in a variety of foods.

Supplement for animal feedsAnimal feeds can be considered important carriers for

health functional compounds like vitamins A and E. These

compounds could be retained in animal tissues and

transferred into animal products such as meat, eggs and

milk. Supplementation of animal feeds with functional

ingredients serves three major benefits; improved animal

health through the supplementation of feedstuffs with

nutrients, excellent protective effect on animal products,

and indirect dietary supplementation of foodstuffs with

nutritional compounds.

The effect of high or low tannin contents of chicken

feeds on growth and mineral absorption was investigated

by Hassan, Elzubeir, and El Tinay (2003), and the

authors found that although tannin addition did not alter

mortality, high tannin supplementation of feeds reduced

the absorption of minerals such as calcium, magnesium,

iron, potassium, sodium, and phosphorous. Studying the

effect of dietary polyphenols on growth and oxidative

stress in chickens, Eid, Ohtsuka, and Hayashi (2003)

reported that dietary polyphenols can reduce growth

inhibition, hyperlipidemia (excess levels of fats in the

blood) and oxidative stress in broiler chickens. Yamane,

Tsuchida, Gotou, Takahashi, and Takeda (1998) claimed

that fowl egg quality could be improved by the additionof tea polyphenols to feedstuffs.

Supplements for feedstuff could be natural or artificial.

For instance, flavonoids can be used as a natural

alternative antioxidant agent to vitamin E. Feeding

chickens with a diet containing 300 mg tea catechins/kg

feed could be as effective as 200 mg a-tocopheryl

acetate/kg feed in the protection of frozen chicken meatagainst long-term oxidation up to 9 months (Tang et al.,

2001b). Tea catechin addition has also a protective effect

on added a-tocopheryl acetate in frozen chicken meat

stored for a year (Tang et al., 2001b). Feeding chickens

with a diet containing tea catechins at a concentration

higher than 200 mg/kg reduces lipid oxidation in chicken

meat, liver and heart (Tang, Kerry, Sheehan, Buckley, &

Morrissey, 2000). Supplementation of feeds with tea

catechins at various concentrations from 50 to 300 mg/kg

has been reported to inhibit the lipid oxidation of chicken

breast and thigh meat stored at K20 8C for a long time.

Supplementing pig diet with a-tocopheryl acetate orgreen tea catechins was able to reduce lipid oxidation in

Longissimus dorsi muscle meat packed aerobically or in

modified atmosphere (40% CO2: 60% O2) w hile

exhibiting insignificant effect on color stability during

storage at 4 8C for 10 days (Mason et al., 2005). On the

other hand, supplementation of cattle diet with 1 g tea

catechins/animal/day failed to have any positive effect on

the color and lipid stability of M. longissimus dorsi

steaks stored aerobically or in modified atmosphere

packaging (30% CO2: 70% O2) while direct addition of

1000 ppm tea catechins to steaks improved the color and

lipid stability of patties significantly (Kerry, 2005). In

conclusion, studies indicate that tea catechins exhibit

in vivo antioxidative activity, and addition of tea

catechins to feedstuff has a protective effect on meat

quality of chicken and pork. However, supplementing

cattle diet with tea catechins fails to improve meat

quality. Differences in effectiveness may arise from

several factors such as differences in digestive systems

(ruminant versus monogastric) and inclusion dose or

form of tea catechins used in feedstuff (Kerry, 2005).

Therefore, more research is needed to determine the

inclusion level effect of tea catechins in feed supplements

on lipid oxidation of beefsteaks or the form of tea

catechins used in animal feeds as a dietary supplement.

Antimicrobial agentAntimicrobial agents can be naturally present in foods,

or added to foods to retard the growth of spoilage

microorganisms or kill pathogens. There are a number of

studies carried out to determine the antimicrobial

effectiveness of phenolic antioxidants in foods. For

example, tannins, polymers of flavanols, have been

reported to inhibit the growth of Aeromonas, Bacillus,

Clostridium botulinum, C. perfringens, Enterobacter ,

Klebsiella, Proteus, Pseudomonas, Shigella, Staphylococ-

cus aureus, Streptococcus, and Vibrio (Chung, Wei, &Johnson, 1998). The antibacterial activity of EGCG on




various strains of Stapylococcus and Gram-negative rods

including Escherichia coli, K. pneumoniae, and Salmo-

nella typhi were determined by Yoda, Hu, Zhao, and

Shimamura (2004). In this study, EGCG inhibited the

growth of Staphylococcus strains at 50–100 mg/mL;

however, concentrations higher than 800 mg/mL wererequired for the inhibition of Gram-negative rods. The

authors explained this difference with the type of cell

wall components since the antibacterial activity of EGCG

could be altered by the presence of peptone and protein

but not amino acids. Amarowicz, Pegg, and Bautista

(2000) showed that proanthocyanidins, epicatechin, EGC

and EGCG fractions of green tea extract and green tea

extract itself have antibacterial activity against E. coli

K12 although the final concentrations of those constitu-

ents of green tea extract were not reported.

Tea catechins have been also tested for the antibacter-

ial activity against Helicobacter pylori, ulcer-causingbacterium. Studying the inhibitory effect of tea catechins,

EGCG and epicatechin, Yee and Koo (2000) found that

both catechins inhibited the growth of H. pylori; however,

EGCG exhibited better inhibitory activity against H.

pylori than epicatechin. Yanagawa, Yamamoto, Hara,

and Shimamura (2003) tested anti- Helicobacter pylori

activity of several catechins including catechin, epicate-

chin, EGC, ECG and EGCG, and their results indicated

that only EGCG and ECG exhibit antibacterial activityagainst H. pylori at 100 mg/mL concentration level. In a

patent, chewing gum containing tea polyphenols is

claimed to prevent viral infections against influenza and

to inhibit dissemination of this virus (Hara & Nakayama,

2001) (Table 2). These studies indicate that tea catechins

contain antimicrobial constituents, and the antimicrobial

activity of catechins depends on several factors such as

type of catechins, concentration of catechins, and type of

microorganisms. In conclusion, antimicrobial activity of

catechins has been and is likely to be exploited for the

purpose of novel applications in food research.

Functional foodFunctional foods are considered as foods with a

physiological purpose in the body. Sanders (1998)

Table 2. Patents related to tea catechins and/or their use in foods (issued by US Patent and Trademark Office)

Date/number Inventor(s) Title Claim/explanation

1989/4,840,966

Hara, Y., and Suzuki, Y. Method of treating hypertension A method for treating hypertension is claimed, andthis method utilizes tea polyphenols includingepigallocatechin gallate, free theaflavin, theaflavinmonogallates A and B, and theaflavin digallate to

maintain or lower blood pressure in humans.1993/5,204,089

Hara, Y., and Hattori, M. Method of preventing the for-mation or aggravation of dentalplaque and method for reducingcariogenesis

Dental plaque, a film of mucus and bacteriadeposited on the teeth that encourages thedevelopment of dental caries, can be prevented byan agent composed of a tea polyphenol orpolyphenols such as catechin, epicatechin, gal-lates of epicatechin, theaflavins and isomers of these compounds.

1998/5,766,595

Yamane, T., Tsuchida, T., Gotou,H., Takahashi, D., Takeda, H.

Method of improving quality of eggs by feeding tea polyphenol

Fowl egg quality can be improved by thesupplementation of feedstuffs with tea polyphe-nols. Eggs produced by this method are claimed tohave ‘a reduced crude fat content, a reducedperoxide content, an enhanced Haugh Unit value,an enhanced degree of transparency of egg white,an enhanced foam-forming ability and a pure

white color in fom and egg white when the eggsare cooked’.2001/6,248,346

Hara, Y., and Nakayama, M. Chewing gum and production of the same

A chewing gum composed of either ‘at least0.03 wt% of at least one tea polyphenol’ withoutany organic acid or ‘at least 0.01 wt% of at leastone tea polyphenol’ with one organic acid isclaimed to prevent viral infections against influ-enza and to inhibit the spreading of this virus.

2001/6,268,009

Ekanayake, A., Bunger, J.R., Moh-lenkamp, Jr., M.J.

Grean tea extract subjected tocation exchange treatment andnonofiltration to improve clarityand color

Treating green tea extracts first with cationexchange resin removes metal cations in theextract, and nanofiltration of the extract at atemperature ranging from about 37 to 60 8Cthrough a membrane produces a permeate of green tea extract. Clarified green tea extracts couldbe added to various beverages and are claimed to

mask undesired aftertaste properties of aspartamein diet beverages.




defined a functional food as “a food or food ingredient

that provides a health benefit beyond satisfying

traditional nutritional requirement”. The definition

implies that functional foods possess physiological effects

that improve human health. Consumer interests towards

functional foods have recently increased sharply becauseof increased consumer awareness on the relationship

between health and nutrition, aging population, more

media coverage on diet-disease interactions, high medical

cost, and increased consumer desire to prevent diseases

rather than cure (Goldberg, 1999; Sanders, 1998).

Plants have been an important part of animal and

human diets due to their functionality in the body. Plant

derived foods provide energy for metabolic activities,

provide precursors for protein synthesis, supply micro-

nutrients for the life like vitamins, essential fatty acids,

and minerals. Moreover, phenolic constituents of plants

are known to have nutritional functions as well asmedicinal. Most of these constituents are secondary

metabolites (Walton, Rhodes, Michael, & Parr, 1999)

and are also called phytochemicals that can be considered

as functional foods since the intake of these substances

improves health by reducing the risk for numerous

diseases. Components of garlic, ginkgo biloba, soybean,

tea, grapes and many other fruits and vegetables are

phytochemicals with dietary importance for humans. Tea,

rich in catechins, is considered to be a functional food for

the improvement of oral health (Wu & Wei, 2002). There

are several patents related with tea polyphenols, especially

catechins (Table 2). Chewing gum containing tea

polyphenols could be used against influenza infections

(Hara & Nakayama, 2001). A substance containing tea

polyphenols such as catechin, epicatechin, gallates of

epicatechin, theaflavin and its monogallates is claimed to

prevent the formation of dental plaque (Hara & Hattori,

1993). Tea polyphenols such as ECG, free theaflavins,

theaflavins monogallate A, theaflavins monogallate B and

theaflavins digallate can also be used to treat hypertension

(Hara & Suzuki, 1989).

Stability and the interaction with food constituents

should also be taken into consideration for commercial

applications of tea polyphenols as a functional ingredient.

Green tea catechins are unstable at high temperatures andpH values, and their stability is poor when stored at room

temperature for a long time (Su, Leung, Huang, & Zhen,

2003). Degradation of EGCG and EGC in sodium

phosphate buffer (pH 7.4) is complete after 6 h of

incubation, and a third of epicatechin and ECG degrade

under similar conditions (Su et al., 2003). Investigating

the effect of various nutrients including catechin on the

formation of resistant starch, Escarpa, Gonzales, Morales,

and Saura-Calixtro (1997) found that catechin reduced the

formation of resistant starch, and showed no influence on

the digestibility of starch.

The use of green tea extracts in foods such as cereals,cakes, biscuits dairy products, instant noodles,

confectionery, ice cream and fried snacks gives ‘a

healthier appeal to the consumer’; therefore, the market-

ing potential for these foods can be improved by the

presence of catechins (Wang, Provan, & Helliwell, 2000).

Mostly, the antioxidative activity of catechins makes

them a potential candidate as a functional ingredient forfoods and beverages.

ConclusionsCatechins are flavanols present naturally in wine, tea,

fruits and chocolate, and this group of flavonoids includes

major catechins such as catechin, epicatechin and gallates of

epicatechin. Catechins are considered as natural antiox-

idants because of their radical scavenging properties.

Catechins can be used in foodstuffs and feedstuffs for

various purposes, for example, to retard lipid oxidation in

oils, fats and animal tissues, to create a value added foodproducts through supplementation with catechins and to

improve the quality of foodstuffs by acting as a functional

ingredient.

Catechins are able to inhibit lipid oxidation in red meat,

poultry and fish (He & Shahidi, 1997; McCarthy et al.,

2001a,b; Tang et al., 2001a, 2001). However, the inhibition

of lipid oxidation in meats is usually dose-dependent. For

the effective inhibition of lipid oxidation in red meat,

poultry, and fish by tea catechins, concentrations higher than

0.3% are usually required. Catechins, especially catechin

and epicatechin, can be also used in peanut oil (Chu & Hsu,

1999) or canola oil (Chen & Chan, 1996) as a naturalantioxidant.

In animal feed studies, tea catechins were found to be

useful for the protection of chicken meat and its products

against lipid oxidation (Tang et al., 2000, 2001b) as well

as for the improvement of animal health (Eid et al.,

2003). Dose or form of tea catechins used in beef cattle

diet may influence the color and lipid stability of M.

longissimus dorsi steaks (Kerry, 2005). In addition to the

studies on the protective effect of catechins against

oxidation, the antimicrobial activity of catechins has been

also investigated in various studies. Although EGCG

inhibits the growth of Staphylococcus strains at 50–

100 mg/mL, higher concentrations (800 mg/mL) are

required for the inhibition of Gram-negative rods (Yoda

et al., 2004). Epicatechin and EGCG have been shown to

have antibacterial activity against E. coli K12 (Amar-

owicz et al., 2000) and H. pylori (Yanagawa et al., 2003;

Yee & Koo, 2000). These studies indicate that catechins

have a potential for novel applications in food research

and this potential is partly due to their antimicrobial

activity.

Catechins include a group of health functional com-

pounds, especially catechin, epicatechin and gallates of

epicatechin, which are major tea catechins. Foods or

supplements containing polyphenols could be used toprevent the dissemination of influenza infections (Hara &




Nakayama, 2001), to prevent the formation of dental plaque

(Hara & Hattori, 1993) or to treat hypertension (Hara &

Suzuki, 1989). In conclusion, there has been a potential for

the novel uses of catechins in foodstuffs and feedstuffs, and

this potential is likely to grow steadily in the future because

catechins contain health beneficial constituents, protect fats,lipids and animal tissues against oxidation, and improve

animal health.

AcknowledgementsThe author would like to thank Dr Joseph P. Kerry,

Department of Food and Nutritional Sciences, University

College Cork, Cork, Ireland, for his valuable comments and

recommendations for the original manuscript.

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