| Tea plant(Camellia sinensis L.O.Kuntze)is a perennial woody plant belonging to the genus Camellia whose fresh leaves have long been consumed by people.With the improvement of living standards,people are looking for tea drinks with better taste and health benefits.In addition,our country is a major producer of tea,but the use of low-grade tea is very low,so the use of tea deep processing technology to develop new products can be used as an important way to improve the utilization of tea in our country.Microbial fermentation of tea drinks is microbes using tea as substrate,through its own physiological metabolism to improve the flavor and quality of tea.Microbial fermentation of tea drinks not only solves the problem of poor sales of low-grade tea,but also to meet the modem demand for healthy functional beverages.In this paper,two kinds of probiotics of Eurotium cristatum and Lactobacillus plantarum were co-fermented with low-grade green tea to develop a flower-flavored green tea beverage.Specific research is as follows:1.Explore the best processing technology of flower-floral green tea beverageUsing the second-level Du Yun Mao Jian tea as raw material,the amount of dry tea added was 1%,the amount of Eurotium cristatum added was 1%,and the sensory evaluation was taken as the selected index.The single-factor test was used to determine the Lactobacillus plantarum added,the amount of sucrose added and the fermentation time,and the optimum technological conditions of the beverage determined by response surface methodology were Lactobacillus plantarum 2%,fermentation time 3 days,and sucrose dosage 7.5%.Under the optimal conditions,the combined sensory score of the flower-floral green tea beverage was 92.5 points.2.The effects of two kinds of probiotics on the volatile components of the flower-floral green tea beverage were exploredHS-SPME-GC-MS method was used to determine the volatile aroma of Eurotium cristatum single fermentation green tea beverage,Lactobacillus plantarum alone fermented green tea beverage,the flower-floral green tea beverage and unfermented green tea beverage obtained under the optimal process conditions substance.We found that the main aromatic components in the flower-flavored green tea beverage are alcohols(30.27%),hydrocarbons(15.25%),aldehydes(11.35%),esters(9.86%)and ketones(9.01%)which are significantly increased compared with the unfermented green tea beverage(P<0.05),which is close to that of the fermented Eurotium cristatum alone,while the aroma substance of the Lactobacillus plantarum fermented tea beverage did not change much,which was close to that of the unfermented green tea beverage.After the fermentation of probiotics,the flower-floral green tea beverage added 2-Pentylfuran,6-Methyl-3,5-heptadien-2-one,3-penten-2-one,Gerany acetone four kinds of aroma substances,and reduce the phenylacetaldehyde and nonyl aldehyde two kinds of aroma substances.3.The effects of two kinds of probiotics on the catechin contents and antioxidation ability in the flower-flavoral green tea beverageWe compared the Eurotium cristatum alone fermented green tea beverage,Lactobacillus plantarum alone fermented green tea beverage and the flower-flavored green tea beverage with the unfermented green tea beverage obtained under the optimal process conditions as a contrast,and we examined the catechins in each group of green tea beverages and three indicators of antioxidant capacity.The results showed that the catechin contents of unfermented green tea beverage group is 1467.36μg/ml.Compared with that,the content of catechins in green tea beverage fermented by Eurotium cristatum alone was 848.72 μg/mL,significantly decreased by 42.16%(P<0.05).The content of catechins in green tea beverage fermented by Lactobacillus plantarum alone and in flower-flavored green tea beverage was 1519.47μg/mL and 1419.94 μg/mL,respectively,which is not significantly changed.Compared with the unfermented green tea beverage,the DPPH radical scavenging ability of Lactobacillus plantarum alone fermented green tea beverage and that of flower-floral green tea beverage were significantly higher than those of the unfermented green tea beverage(P<0.05).In ferric ion reduction ability and ABTS+free radical scavenging ability,the Eurotium cristatum alone fermented green tea beverage was significantly lower than the other three groups(P<0.05),and Lactobacillus plantarum alone fermented green tea beverage has the highest antioxidant capacity,although the flower-flavor green tea beverage is higher than the unfermented green tea beverage,but the difference was not significant.4.The effect of two kinds of probiotics on the catechins in the flower-flavoral green tea beverage was exploredWe have studied the dynamic changes of polyphenols,the dynamic changes of pH and the dynamic changes of the growth of Eurotium cristatum in Lactobacillus plantarum alone fermented green tea beverage,Eurotium cristatum fermented alone fermented green tea beverage,flower-flavored green tea beverage and unfermented green tea beverage in the process of fermenting five days.And the catechins change in the green tea beverages fermented by Eurotium cristatum in the acidity condition in the process of fermenting five days.The results showed that,in the total catechin contents,unfermented green tea beverage from 1375.44 μg/mL reduced to 1336.99μg/mL,the change was not significant(P<0.05);Lactobacillus plantarum alone fermented green tea beverage significantly increased from 1375.44μg/mL to 1471.31μg/mL(P<0.05),increased by 6.97%;Eurotium cristatum fermented alone fermented green tea beverage significantly decreased from 1375.44μg/mL to 863.96 μg/mL(P<0.05),decreased by 37.19%,among them,the amount of ester-type catechins was significantly decreased(P<0.05)and the content of non-ester catechins was significantly increased(P<0.05),and the content of ester-type catechins decreased much more than that of non-ester type catechins.The flower-flavored green tea beverage decreased significantly from 1375.44 μg/mL to 1216.48 μg/mL with a decrease of 1 1.56%(P<0.05).In the dynamic changes of pH,the unfermented green tea beverage maintained at around 5.5;the Eurotium cristatum alone fermented green tea beverage maintained at about 4.5;Lactobacillus plantarum alone fermented green tea beverage and the flower-flavored green tea beverage were maintained at about 3.5.It was found that the total catechin contents of Eurotium cristatum alone fermented green tea beverage increased significantly from 1587.36 μg/mL to 1664.01 μg/mL when controlled the beginning fermented pH at 3(P<0.05).When fermented conditions were controlled at pH=4 and under natural fermented conditions,the total catechin contents were significantly reduced(P<0.05).Finally,the dynamic changes of the growth of Eurotium cristatum was presented by the Eurotium cristatum dry weights.The Eurotium cristatum dry weights of Eurotium cristatum fermented alone fermented green tea beverage increased from 0.03 g/100 mL to 0.41 g/100 mL,showing a S-curve dynamic change;while the flower-flavored green tea beverage increased from 0.03 g/100 mL to 0.18 g/100 mL,which the growth curve is more gentle. |
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