TITLE:
Effect of Citric Acid on the Total Monomeric Anthocyanins and Antioxidant Activity of Liquor Made from Unprocessed Purple Leafed TRFK 306 Kenyan Tea Clone
AUTHORS:
Emily C. Kilel, John K. Wanyoko, Abdul K. Faraj, Peninah Ngoda
KEYWORDS:
TRFK 306, Total Monomeric Anthocyanins, Antioxidant Activity, Citric Acid, Brewing Conditions
JOURNAL NAME:
Food and Nutrition Sciences,
Vol.10 No.10,
October
11,
2019
ABSTRACT: A study was conducted to find out the effect of citric acid on total
monomeric anthocyanins and antioxidant activity of liquor made from unprocessed purple-leafed TRFK 306
Kenyan tea, brewed at various time/temperature combinations. Most
purple tea consumers usually brew the tea leaves then add some lemon juice
before consuming it. Citric acid was used here to mimic the use of lemon juice.
Documentation on the quality of such a brew is scanty and the effect of acid on
its quality is equally scanty. The current study used brewing time/temperature
combinations of 5, 10 and 15 minutes with 70°C and 92°C drinking water. Total monomeric anthocyanins
were analysed using UV-1800
spectrophotometer (Shimadzu, Japan) while DDPH method was used to assay for
antioxidant activity. Citric acid concentration of 0, 0.1% to 0.5%
was used to check their effect on the brews with the highest total anthocyanins and antioxidant activity. The results showed that brewing temperature of 70°C had 9.5 mg/L to 27.7 mg/L, with 5 minutes brewing
time being the highest. Temperature of 92°C had 37.5 mg/L to 92 mg/L with 5 minutes
brewing time having the highest total monomeric anthocyanins. Antioxidant
activity of 92°C brewing temperature ranged from 90.7% to
92.0%. Total monomeric anthocyanins increased with increased citric acid concentration up to 0.3% before it decreases while for
antioxidant activity, it decreased with addition of citric acid. It was concluded that
for maximum anthocyanins extraction, 5 minutes brewing time is the best while
ten minutes brewing time could give optimum antioxidant activity.