A Study On Maintenance Of Volatile Compounds And Related Processing Parameters Of Ready-to-drink Green Tea

Volatile constituents and their concentration of tea liquors extracted from green tea "Sanbeixiang" produced in Zhejiang Taishun were investigated by GC/]MS HPLC color difference meter, successive distillation extraction (SDE). Effects of extraction temperature, extraction duration and ratio of tea to water on volatile constituents in the green tea liquor were studied. Effects of heating treatment, β -glucosidase and L-ascorbic acid on color differences and major chemical components of the green tea liquor were also investigated. The results obtained were as follows:1 .The volatile constituents in the green tea liquor were lost greatly during high temperature extraction while lower temperature (50℃), shorter duration (10min), and bigger ratio of tea to water (1/40~1/60) maintained a higher concentration of the volatile constituents.2, Concentration of tea polyphenols decreased significantly and that of amino acids increased while concentration of caffeine did not changed significantly during high temperature sterilization; Concentrations of EGC, EC EGCG ECG decreased whereas GC C GCG CG decreased with increase of sterilization temperature. However, L-ascorbic acid could prevent epicatechins from conversion into non-epicatechins during high temperature sterilization treatments.3.Heating treatment could induce lightness and greenness of the green tea liquor decreased and yellowness increased. Microwave treatment had a lighter effect on the color, high temperature treatment made the lightness and greenness of green tea liquor markedly decreased and the green tea liquor became deeper in red color. The effect of heat treatment on conversion of catechins was dependent on the heating methods. The changed from epicatechins to non-epicatechins was less by microwave heating than that by autoclave heating. However, the conversion of from epicatechins to non-epicatechins depended on the microwave heating duration and temperature and more epicatchins were changed to non-epicatechins by longer duration and higher temperature treatments than those by shorter duration and lower temperature. Volatilecomposition and total concentration of volatiles components changed during autoclave heating treatment. Three volatile components were decreased while eight volatile components increased with the duration of microwave treatment. Eight volatile components decreased and ten volatile components increased with increase of temperature in autoclave.4.The volatile constituents in green tea liquor were enhanced significantly by teatment of β -glucosidase and its optimum enzymolysis conditions were temperature 50℃ for 100~140 min and the enzyme volume of added enzyme 15u/L.