INTERNATIONAL JOURNAL OF AGRICULTURE & BIOLOGY
Effect of Time and Temperature on Infusion of Tannins from
Commercial Brands of Tea
SALIM-UR-REHMAN, KAUSAR ALMAS†, NAUREEN SHAHZADI, NIGHAT BHATTI† AND ASIMA SALEEM
Departments of Food Technology and †Home Economics, University of Agriculture, Faisalabad–38040, Pakistan
Effect of various times (2, 4, 6, 8, 10 min), temperatures (90, 95, 100°C) on tannin extraction from commercial brands of tea
i.e. Lipton Danedar, Lipton Taza and Lipton Yellow Label and its effect on egg protein solubility was investigated. A
significant increase in tannin contents and significant decrease in KoH solubility of protein with increase in time and
temperature were recorded. Moisture, ash and water soluble ash contents of Lipton Danedar were significantly highest among
brands, where as alkalinity of water soluble ash, crude protein, crude fat and crude fibre of Lipton Yellow Label were found
higher than that of Lipton Taza and Lipton Danedar. The data of sensory evaluation revealed that Lipton Yellow Label
exhibited a highly significant differences in colour, taste, flavor and overall acceptability as compared to Lipton Taza and
Key Words: Tea; Tannins; Commercial brands; Protein solubility
commercial brands of tea, Lipton Danedar, Lipton Taza and
Lipton Yellow Label were purchased from local market.
(Camelia sinensis) is one of the most widely
Tea extracts were prepared using various cooking
consumed beverages due to its health giving dietetic and
times (2, 4, 6, 8 and 10 min) and temperatures (90, 95 and
therapeutic qualities. Tannins are water soluble polyphenol
compounds having wide prevalence in plants. It is a
Chemical analysis. Moisture, ash, alkalinity of water
powerful stringent and to some extent an irritant. Its
soluble ash, crude protein, crude fat and crude fiber of each
properties depends on the formation of insoluble compounds
brand of tea were determined according to the standard
but as the process of digestion progress the stomach contents
methods (Harold et al., 1981).
become more acidic. The protein tannate break up and some
Sensory evaluation. Tea infusions were evaluated for color,
of the combined tannins pass into intestine and decrease
taste, flavor and overall acceptability by panel of Judges on
secretion of small intestine which produced constipation
nine points hedonic score (Land & Shephered, 1988).
(Bhat et al., 1998; Reed, 1995). Excessive intake of tannins
Preparation of tea infusion. Each tea infusion was
may cause insomnia, nausea, vomiting, palpitation of heart
prepared by taking 3 g of tea in 400 mL distilled water from
and a cup of tea after meal may cause dyspepsia (Chung et
each brand of tea (AOAC, 1990). The solubility of egg
Tea during meals significantly inhibits the
protein was determined by method of AOAC (1990). The
absorption of both food iron and medicinal iron (Disler et
data were analyzed statistically by using Analysis of
al., 1975). Protein digestibility was greatly reduced when
Variance Technique (Steel & Torrie, 1984).
tanniferous was the part of diet (Giner-Charved, 1996).
Small quantities of tannins in diet caused adverse effect in
RESULTS AND DISCUSSION
poultry (Haslan, 1989). It has been observed at public places
and road-side tea shops, in Pakistan that the procedure for
The results showed a significant increase in tannin
tea making generally consists of repeatedly and prolong
contents and significant decrease in KoH solubility of
boiling of tea for maximum extraction of colour and taste
protein with increase in time and temperature.
which otherwise may be harmful.
On two minutes cooking, the tea brand Lipton Taza
Taking in view the above facts, this project was
showed a highly significant negative correlation between
designed to assess the effect of time and temperature on the
tannin extraction and protein solubility with increase of
extract of tannins and its effect on protein solubility.
temperature (r = -0.097, P<0.0001) as compared to Lipton
Danedar as shown in Fig. 1. The effect of temperature on
MATERIALS AND METHODS
rate of extraction of tannins of all the brands was non-
significant. These results were found in accordance with the
These studies were carried out at University of
Agriculture, Faisalabad, during 1999-2000. Commonly used
findings of Savolainen (1992) who found that the tea
BOILING EFFECT ON TANNINS AND PROTEIN SOLUBILITY OF TEA / Int. J. Agri. Biol., Vol. 4, No. 2, 2002
Tannin extraction and protein solubility of three spectrophotometry. Heating for 2 min at three
commercial brands of tea cooked for two (Fig. 1), four temperatures revealed a significantly higher amount of
(Fig. 2) and six (Fig. 3) minutes at 90, 95 and 100°C. LD= soluble protein in Lipton Yellow Label followed by
Lipton Danedar; LT= Lipton Taza; LY= Lipton Yellow
Lipton Danedar. Heating for 4 minutes at three
temperatures revealed significantly the highest amounts
of tannin extraction in Lipton Taza which were 7.83, 7.85
and 7.87% at 90, 95 and 100°C, respectively (Fig. 2).
Lipton Yellow label showed increase in tannin contents
and decrease in protein solubility which is highly
significantly correlated (r = -0.602; P<0.08) as compared
to Lipton Taza and Lipton Danedar (r = -0.44; P<0.23) (r
= -0.35; P<0.36). Effect of all temperatures on tannin
extraction on three brands of tea was found non-
significant. Panda et al. (1981) has estimated tannin from
tea dust by boiling and direct infusion from 4-6 min to be
122-128 mg and 150-165 mg/100 mL, respectively. The
deception in the results obtained in the present
investigation from that of panda et al. (1981) may be due
to difference in boiling periods and varieties of the tea.
On 6 min cooking, Lipton Taza showed a higher
extraction of tannin while Lipton Danedar exhibited
higher protein solubility as compared to other brands.
Lipton Taza showed the lowest significant negative
correlation (r = -0.28; P<0.46) as compared to correlation
of Lipton Danedar and Lipton Yellow Label (Fig. 3).
Similar trend was observed in case of 8 and 10
minutes cooking with respect to tannin extraction and
protein solubility (Fig. 4, 5). Proximate analysis showed
that moisture, ash and water soluble ash of Danedar were
significantly highest among Lipton Taza and Lipton
Yellow Label, whereas alkalinity of soluble ash, crude
protein, crude fat and crude fibre of Lipton Yellow label
were highly significantly highest than the Lipton Taza
Fig. 4. Tannin extraction and protein solubility of
three commercial brands of tea cooked for eight
minutes at 90, 95 and 100°C. LD= Lipton Danedar;
LT= Lipton Taza; LY= Lipton Yellow
contained 3.7% tannic acid, which was analyzed by
REHMAN et al. / Int. J. Agri. Biol., Vol. 4, No. 2, 2002
Fig. 5. Percentage of tannin extraction and protein CONCLUSIONS
solubility of three commercial brands of tea cooked for
10 minutes at 90, 95 and 100°C. LD= Lipton Danedar; LT=
These studies revealed that the tannin contents
Lipton Taza; LY= Lipton Yellow
increased with an increase in boiling time and protein
solubility was decreased with an increase in tannin
concentration. Since it is harmful in large doses, it is
necessary to avoid the prolong boiling as commonly
practiced in hotels and road side tea shops in Pakistan in
order to get the maximum extraction of color and briskness
which is not suitable. Prolong boiling causes decrease in
sensory properties i.e essential oils responsible for aroma of
tea are also lost on boiling due to their volatility. Two
minutes boiling is sufficient for tea making in order to get a
good ratio of tannins.
AOAC, 1990. Association of Official Analytical Chemists. Analytical
chemists. 15th ed., Arlington, USA.
Bhat, T.K., B. Singh and O.P. Sharma, 1998. Microbial degradation of
tannins a current perspective. Biodegradation, 9: 373– 57.
Chung, K.T., T.Y. Wong, C.I. Wei, X.W. Huang and Y. Lin, 1998. Tannins
and Lipton Danedar as shown in Table I.
and Human health. Critical Review. Food Sci. Nutr., 38: 421–64.
Disler, P.B., S.R. Lynch, R.W Charlton, T.D. Torrence, T.H. Bothwell, R.B.
Table I. Proximate analysis of common commercial
Walker and F. Mayet, 1975. The effect of tea on iron absorption. Gut,
brand of tea
Giner–Charved, B.I., 1996. Condensed Tannins in Tropical Forages. Ph.D.
Thesis, Cornell Univ., Ithaca, New York.
Harold, E., S.K. Ronald and S. Ronald, 1981. Pearson's Chemical Analysis
of Food. 8th ed., pp: 286–312. Longman Group, U.K.
Haslan, F., 1989. Plant polyphenols. Cambridge Univ. Press Cambridge
U.K. (Nutri. Absts and Reviews, 63: 5728, 1993).
Water soluble ash (%)
Land, D.G. and R. Shepherd, 1988. Scaling and ranking methods. In: Piggot,
Alkalinity soluble ash
1.20±0.011 1.24±0.005 1.46±0.011
J.R. (Ed.), Sensory Analysis of Food, pp: 155–85. Elsevier Applied
Sci., New York.
Crude protein (%)
Panda, N.C., S.K. Panda, A.G. Rao and B.K. Sahu, 1981. Damage done to
Crude fat (%)
intestine, liver and kidney by tannic acid of tea and coffee. Indian J.
Crude fibre (%)
Nutr. Diet., 18: 97–103 (Chem. Abst., 96: 5054N; 1982).
Reed, J.D., 1995. Nutritional toxicology of tannin and related polyphenols in
When the data of sensory evaluation were analyzed,
forage legumes. J. Animal Sci., 73: 1516–28.
Lipton Yellow Label exhibited highly significant difference
Savolainen, H. 1992. Tannin contents of tea and coffee. J. Appl. Toxicol., 12:
for color, taste, flavor and overall acceptability as compared
to Lipton Taza and Lipton Danedar as shown in Table II.
Steel, R.G.D. and J.H. Torrie, 1984. Principles and Procedure of Statistics,
2nd Ed., pp: 173–7. McGraw Hill Book Co. Inc. Singapore.
Table II. Sensory evaluation of commercial brands of
(Received 04 January 2002; Accepted 10 March 2002)
Overall acceptability 6.66±0.57B 8.00±1.00AB 8.66±0.57A