Comparative analysis on chemical components and antioxidant activity for aged Wuyi rock teas in different years

【Objective】 In order to provide a theoretical basis for the food safety, processing, storage of Wuyi rock tea, the content of acrylamide, quality component content and antioxidant capacity of Wuyi rock tea in different storage years were analyzed.【Method】 In this study, main chemical compositions contents such as acrylamide content and free amino acid and the 1, 1-diphenyl-2-trinitrophenylhydrazine(DPPH) radical scavenging abilityof short leg oolong Wuyi rock tea with different storage years0(new tea), 2, 4 and 6 yearswere determined by ultra high performance liquid chromatography(UHPLC) and spectrophotometry. The correlation between acrylamide, main quality chemical compositions and antioxidant capacity of Wuyi rock tea in different storage years was analyzed.【Result】 The results showed that the contents of acrylamide of Wuyi rock tea with 0(new tea), 2, 4 and 6 years were low, which were 304.67, 255.09, 188.19, 172.45 ng/g, respectively, and they were all within the safety limit of EU regulations(≤850 ng/g). The contents of acrylamidein storage period of 2, 4 and 6 years were declined extremely compared with the fresh tea(P<0.01, the same below). The content of free amino acids was 2.85% after storage for 2 years, which was significantly lower than new tea by 44.5%(P<0.05, the same below). With the increase of storage years, the contents of tea polyphenols, catechins, caffeine, moisture extracts and antioxidant activity showed a downward trend at each storage year, while the opposite trend was observed for total sugar contents. Pearson correlation analysis showed that there was extremely significant positive correlation between acrylamide, caffeine, catechins and storage time, free amino acids content was significantly negatively correlated with storage time, catechins content was extremely positively correlated with acrylamide content, and free amino acids content was extremely negatively correlated with antioxidant activity.【Conclusion】 With the increase of storage years, most of the main chemical components of Wuyi rock tea show a downward trend. The content of acrylamide in Wuyi rock tea is low and will not pose risk to human body, so consumers can drink it safely.