Effects of different extraction time and temperature on infusion amounth of phenolics and alcaloids

In this study the effect of different extraction time and temperature on phenolic and flavonoid compounds of tea was investigated. For this purpose, different classes of black tea (2, 5, and 7) obtained from Çaykur were harvested in 2010 May. On the other hand, samples were purchased from the market. All tea samples were extracted five different times (3, 8, 15, 20 and 30 minutes) at two different temperatures (90, 100°C). For the amount of total phenolics, flavonoids and their composition were determined. Furthermore, moisture, extraction yield and antioxidant activity of the samples were evaluated. Results showed that total phenolics and flavonoid contents of the green tea samples were higher than that of the black tea samples. Significant differences were found on the phebolic and flavonoid compounds of the green tea samples. In addition, the 2nd class of the black tea samples had the highest phenolic and flavonoid concentration which was followed by 5th and 7th classes, respectively. Moreover, the effects of tea classes extraction time and temperature were found to be significant on the phenolic and flavonoid contents of the tea samples.The main phenolic compounds of the black tea samples were identifid as gallic acid (GA), (-)-gallocatechin (GC), (+)-catechin (C), (-)epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-catechin gallate (CG), theaflavin (TF-f) and theaflavin-3-3?digallat (TF-3,3?-DG).While the phenolic compounds of the green tea were identifid as gallic acid (GA), (-)-gallocatechin (GC), (+)-catechin (C), (-)epigallocatechin (EGC), (-)-epigallocatechin gallate (EGCG), (-)-epicatechin (EC), (-)-epicatechin gallate (ECG), (-)-catechin gallate (CG). In addition, alkaloids such as caffeine and theobromine of the samples were significantly changed by the classes of the tea and extraction conditions. In conclusion, the highest extraction yield, phenolic content and antioxidant activity of the samples were determined for 30 min extraction at 100°C.KEY WORDS: Green tea, black tea, phenolic compounds, antioxidant activity,