ANTIOXIDANT PROPERTIES IN GREEN TEA AS INFLUENCED BY PROCESSING TECHNIQUES
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Date
2017-07
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Publisher
AAU, Jorhat
Abstract
Tea (Camellia sinensis) is primarily processed as black tea or green tea.
Tea is one of the most widely consumed beverages worldwide due to the associated
health benefits. In the recent past, consumer preference has been shifting towards green
tea. The techniques of manufacturing green tea are relatively uncomplicated. Small tea
growers in Assam have started manufacturing green tea from tea leaves plucked from
their small holdings. However the techniques of manufacture vary among the processing
units. Variations also exist in the manufactured tea depending on geographical conditions
and planting materials used.
A study was carried out at Assam Agricultural University, Jorhat, to
ascertain the variation in antioxidant properties as influenced by processing techniques.
Green tea samples were collected from green tea manufacturers with different techniques
of manufacture, during different flushes of tea, in April, May, August and October. The
experiment was laid out in factorial completely randomized design with six treatments
considering the processing techniques and the four different months of manufacture. The
data revealed that the moisture content was highest in green tea manufactured during the
month of August with 6.76% in treatment T6 (pan roasting) and low in green tea
manufactured during October with 3.30% in treatment T3 (dipped in boiling water 1
minute). The mean highest moisture content was found to be in the range of 4.47% in
green tea manufactured in April to 6.51% in green tea manufactured in August.
All the manufactured green tea samples were bright greenish yellow in
colour with good cup characteristics. Biochemical analysis of the samples revealed that
green tea manufactured by the treatment T1 (steamed for 30 seconds) was the best among
all the treatments and had highest antioxidant properties. Mean total polyphenol content
was found to be in the range of 11.61 mg catechol equivalent g-1 to 15.42 mg catechol
equivalent g-1, with highest polyphenol observed in the treatment T1 (steamed for 30
seconds) in green tea manufactured during August (20.38 mg catechol equivalent g-1).
Mean total flavonoid content was highest in treatment T1 (steamed for 30 seconds) with
22.62 mg quercetin equivalent g-1 and the lowest in treatment T6 (pan roasting) with
18.23 mg quercetin equivalent g-1.Total flavonoid content was highest in treatment T1
(steamed for 30 seconds) with 23.91 mg quercetin equivalent g-1 in green tea
manufactured during August and was lowest in treatment T2 (dipped in boiling water for
10 seconds) with 13.66 mg quercetin equivalent g-1 in green tea manufactured during
April. The Total Antioxidant Activity was measured with the help of DPPH and it was
expressed in percentage inhibition. Total antioxidant activity was highest in treatment T1
(steamed for 30 seconds) in green tea manufactured during August (85.03%) and lowest
in treatment T6 (pan roasting) in green tea manufactured during April (61.33%). The
mean highest antioxidant activity (78.76%) was recorded in treatment T1 (steamed for 30
seconds) and mean lowest antioxidant activity (73.37%) was recorded in treatment T3
(dipped in boiling water for 1 minute). The inhibition percentage was higher in green tea
manufactured during August for all treatments.