Effect of different shaping drying condition on volatil aroma components in famous Keemum black tea

Using headspace-solid-phase micro-extraction coupled with gas chromatog-raphy-mass spectrometry(HS-SPME-GC-MS),the aroma components in Keemum black tea after different drying treatments were detected,which included a 2×2×3 factorial randomized grouping design plus 2 control groups,2 drying methods,2 water content and 3 temperatures as independent variables,14 treatments in total. Drying methods by hand and by machine,were noted as S and J. Initial moisture contents were 15% and 20%,noted as A1,A2 and A3.Drying temperatures were 110,130 and 150 ℃,noted as B1,B2 and B3.The results showed a total of 105 aroma components were identified in these 14 samples,mainly including 7 kinds of compounds such as alcohols,aldehyde,and esters etc. Among these,alcohols were the most in abundance,followed by aldehydes,esters and hydrocarbons. The most aroma components(70 types)were detected in the drying group SA1B3,which contained 15 components more than the control. The fewest were group SA2B2 and JA2B1,only 47 components in each,which lower than control groups. Comparing average relative percentage of all kinds of aroma components between the two drying methods,the contents of aldehyde,ketone and hydrocarbons were higher in drying by hands by 10.76%,11.67% and 3.09%,the contents of esters were lower in drying by hand by 21.53%,respectively. Some aroma compositions were not founded in each drying methods. Therefore,differences of aroma components in kind and quantity of famous Keemum black tea were caused by different drying treatments.The optimal drying method was shaping and drying should be handworked,the shaping in which should be at the temperature of 150 ℃,and the moisture content for the tea leaves ought to be 15% before the process.