Effects of Tea Processing Procedures on Chemical Components and Antioxidant Activity of Coffee Leaves

In the present study,coffee leaves were processed using tea processing methods and the effects of tea processing steps(including withering,rolling,fermentation,and drying)on the proximate and phytochemical compositions and antioxidant activities of coffee leaves with different developing stages were investigated. The results showed that each processing step and age of leaves affected proximate and phytochemical compositions and antioxidant activities differently. In generally,water soluble content exhibited a decrease tend;soluble sugars decreased during the first three processing steps with an increase during drying;withering caused the increase of free amino acid(FAA),however,FAA decreased when the leaves underwent fermentation. Caffeine content decreased significantly(P<0.05)in young leaves during processing,whereas,it remained constant in mature leaves;mangiferin and rutin contents increased during withering followed a decrease in the rolling and fermentation and then increased again during drying;chlorogenic acids kept decreasing before the end of fermentation and then increased in the drying process;the temporal profiles of total phenolic and total flavonoid contents and the antioxidant activity were similar to that of chlorogenic acids. Fresh young coffee leaves have greater water content,soluble sugar and soluble protein,phytochemical composition and antioxidant activity than that of mature leaves and those responses were significantly different in the same processing steps. Increase of fermentation time from 2 h to 48 h caused the decreases of proximate and phytochemical compositions and antioxidant activity significantly. In conclusion,different tea processing steps have different impacts on the phytochemical composition and antioxidant activity. Different tea processing steps have different impacts on the phytochemical composition and antioxidant activity of coffee leaves and fermentation time was the most significant factors that affect the proximate composition and phytochemical components other than moisture.