| Tea plant(Camellia sinensis L.0.Kuntze)was a kind of perennial woody plants classified to Camellia Theaceae.The fresh buds and leaves after harvest could be made processing into tea.Fu-brick Tea was a type of dark tea belonging to one of the six tea categories.The processing technologies for Fu-brick tea were very complex.In essence,the“golden flower appearing,was the growth phenomenon of the predominant fungus(Eurotium cristatum).The metabolites in the tea had been changed in this process,and the active substances had been produced from fUngus.lt not only made Fu-brick tea have the special characteristics which is distinguishable from other types of tea,but also be good for lipid-decreasing,weight loss,digestion promotion and antioxidant.Improving the aroma was important for the development of the tea beverage products because the aroma components were the key quality for the tea.Till now,studies of the fermentation by Eurotium cristatum in tea beverage were mainly focused on optimization and the dynamic changes of the biochemical components during the fermentation.One liquid beverage which the extract of the low-grade green tea and black tea were fermented by Eurotium cristatum was made in this study.Also the changes of aroma and biochemical components were investigated druing the processing.The results are as follows:(1)By single-factor experiment,it was found that the optimum choice of sucrose concentration was 6%and the ration between tea and water(g:mL)was 1:30 in the medium for Eurotium cristatum liquid fermentation.It was found that Eurotium cristatum grew rapidly in the 0～96h,and the value of OD600 reached its maximum at the 96h.It was found that the pH value decreased in the 0～96h and then increased after 96h,but it decreased mainly during the fermentation.It was found that the color in green tea extracts changed to yellow,and in black tea extracts changed to brown during the fermentation.It was found that the contents of tea polyphenols showed a trend of gradually reduce,and so does the contents of catechin during the fermentation.It was found that the content of caffeine decreased a little.(2)The aroma components of the green and black tea extracts were quantified by HS-SPME-GC-MS before and after fermented by Eurotiumcristatum.It was found that the majority of the volatiles were diminished or reduced during extraction and sterilization.Benzoic acid methyl ester,isophorone,methoxy styrene,ethyl benzene,formaldehyde,sweet folic acid methyl ester,and 3,4-dimethyl methyl benzoic acid were six compounds that were not contained in the raw extracts of green and black tea and were newly synthesized during fermentation.In the green tea extracts,the content of linalool was elevated by 2.30 fold than the raw material after fermented by Eurotium cristatum.Similarly,the linalool oxide Ⅰ enhanced by 3.15 fold,and the linalool oxide Ⅱ increased by 3.04 fold,as well as 1.29 fold in methyl phenylacetate,4.18 fold in Alpha terpineol,1.10 fold in trans-2-decylolefine aldehyde,3.08 fold in α-ionone.It turned out that fermentation would can play an efficient role on the aroma components in green tea extraction.However,the contents of aroma components were observed decreased in the black tea extracts after fermentation.(3)The activity of β-D-glucosaccharase was measured by the p-PNG method in the green and black tea extracts during fermentation.It turned out that the β-D-glucosaccharase activity increased gradually as the time going by,and consequently got to a stable level after 96h.The β-D-glucosaccharase activity reached the peak level of 27.65 U/mL at the 108 h in the green tea extracts,and 21.87U/mL in the black tea extracts. |
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