| Red globe grapes are characteristic by sweet taste,plump fruit,and certain function,are rich in a variety of nutrients such as fructose,minerals and vitamins.At present,most of the red globe grapes on the market are fresh,and the types of intensively processed products are single.Therefore,the development of new functional products of red globe grapes is of great significance to promote the development of the red globe grape industry.Therefore,in this study,Xinjiang red globe grapes were used as raw materials,Lactobacillus acidophilus-CGMCC22771 and Lactobacillus plantarum-CCTCCM2019497 were selected as starters.Red globe grape juice fermented by lactic acid bacteria were developed by comparing different fermentation processes,and their quality and flavor were evaluated.The research results are as follows:(1)To determine the fermentation process of red globe grape juice fermented by lactic acid bacteria:Sensory score and viable count was selected as indicators.Through the single factor experiment and optimized by response surface experiment,the process parameters of lactic acid bacteria fermented red globe grape juice were as follows: the material-liquid ratio was 4:1,Initial soluble solids content was14 °Brix,the initial p H was 4.0,inoculation method was mixed fermentation of two bacteria in equal ratio(1:1),the amounts of bacteria added was 0.07%,fermentation temperature was 37 °C and fermentation time was 48 h.According to this process,the sensory score of red grape juice fermented by lactic acid bacteria was 93 points,and the number of viable bacteria could reach 8.0 lg CFU/m L.(2)Study on functionality properties and shelf life of red globe grape juice fermented by lactic acid bacteria: In terms of function content,the fermentation group of LA&LP(1:1)> the single fermentation group of LA and LP > the control group.Compared with control group,the contents of total flavonoids,total anthocyanins and total phenols in LA&LP(1:1)fermentation group were increased by 100.00%,115.00% and 44.40%,In the determination of DPPH antioxidant activity,compared with the control group,the antioxidant activity of LA&LP group was increased by 27.00%(p < 0.05);In the determination of ABTS+ antioxidant activity,compared with the control group,the antioxidant activity of LA&LP group was increased by 46.00%(p < 0.05).The shelf life conditions: the average change rate of each index was24.49% after storage for 28 days under 4 ℃.Under this condition,the product quality was relatively safe.In addition,various indicators of the product stored at 4 ℃ and 25 ℃ were monitored.The soluble solid content was 13.2 °Brix,the p H was 3.71,and the total acid was 5.62 g/L,the total number of viable bacteria was more than 6.0 lg CFU/m L,and the sensory score was 90.(3)Determination the taste and flavor substances of red globe grape juice fermented by lactic acid bacteria: Electronic tongue test showed that compared with the control group,the response values of sour,umami and richness in fermentation group were increased by 100.00%,84.00% and 435.70%,respectively,the response values of bitterness and astringency had little change.The difference of taste characteristics in the experimental group was small,but the acid taste of LA&LP-48 h fermentation group was more prominent.Electronic nose experiment showed that the response values of aromatic and aliphatic compounds in fermentation group were increased by 41.80% and 58.80% respectively,while the response values of other sensors had little change.LA&LP-48 h mixed fermentation group had the highest total response value(11.08)and the most significant aroma(p < 0.05).In addition,a total of 57 substances were identified by HS-SPME-GC-MS technology,including 14 esters,12 acids,10 alcohols,6 aldehydes,7ketones,3 phenols,and terpenes.3 species and 2 other compounds.Compared with the control group,the contents of ethyl acetate,octanoic acid,ethyl benzoate,octanoic acid,benzoic acid and 2-hexenol in red globe grape juice fermented by lactic acid bacteria increased.The contents of ethyl acetate and 2-hexenol of acetic acid in LA&LP-48 h group were significantly accumulated,which gave more richer aroma to red globe grape juice fermented by lactic acid bacteria. |
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