茶叶加工过程对咖啡叶化学成分和抗氧化活性的影响

本研究采用茶叶加工方法对咖啡叶进行加工，探索茶叶加工步骤（包括萎凋、揉捻、发酵、干燥）对不同叶龄咖啡叶的基础成分、植物化学成分和抗氧化活性的影响。结果表明，加工步骤和叶龄对基础成分、植物化学成分和抗氧化活性有不同程度的影响。咖啡叶中水浸出物的含量在整个加工步骤中总体呈下降趋势；可溶性糖的含量在前三个步骤中呈下降趋势，但是干燥后其含量有所上升；萎凋使咖啡幼叶中的游离氨基酸含量提高，然而从发酵步骤开始降低。咖啡因含量在幼叶中呈降低趋势但在成熟叶中变化不显著；芒果苷和芦丁含量在萎凋时升高，揉捻和发酵时降低，干燥时升高；绿原酸含量在发酵步骤结束之前呈下降趋势，干燥时又升高；总酚和总黄酮含量以及抗氧化活性的基本变化趋势与绿原酸相似。鲜咖啡幼叶的水分含量、可溶性糖、可溶性蛋白、植物化学成分和抗氧化活性均显著高于成熟叶且在相同步骤下其含量在幼叶与成熟叶中存在显著性差异。发酵2 h的基础成分含量、植物化学成分含量和抗氧化活性高于48 h。不同茶叶加工步骤对咖啡叶的植物化学成分和抗氧化活性具有不同的影响，其中发酵的时间对除了水分之外的基础成分和植物化学成分的影响最为显著。

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.