| Edible Jiaosu refer to products that use plants that can be used for food processing as the main raw material,with or without auxiliary materials.It are produced by microbial fermentation and contain specificbiologically active ingredients that can be consumed by humans.Jiaosu have been greatly studied in Japan.Currently,it is still in the initial stage of development in the mainland,and most of Jiaosu products on the market are made by natural fermentation.The fermentation cycle is long and the product quality has unstable factors.Therefore,the inoculation fermentation has become an alternative method.However,the microbial,fermentation mechanism and product functional components of Jiaosu fermented by inoculation are still to be studied.In this project,suitable fermentation strains were selected from different yeasts and lactic acid bacteria,The compounds change law of inoculation fermentation to prepare grape Jiaosu was analyzed.The bioavailability of grape Jiaosu polyphenols was revealed.This study opens up new ways for the utilization of grape resources and provides a theoretical basis for the development of controllable grape Jiaosu.The main findings are as follows:1.The fermentation characteristics and metabolites of different yeasts and lactic acid bacteria were compared in order to screen suitable strains for grape Jiaosu.Studies have shown that Saccharomyces cerevisiae JL-11,JL-24,CL-13 and XQ-05 grow fast in the substrate and have strong ability to consume sugar.The soluble solid content decreased from 18 to 5°Brix in the first two days of fermentation.The acid production capacity of Saccharomyces cerevisiae XQ-05 was significantly higher than other strains.For SOD production capacity,Pichia kudris CL-19 and Pichia fermentative CL-03 were higher,followed by Saccharomyces cerevisiae JL-24,JL-11 and CL-13,Both Pichia manchuria JL-25 and Saccharomyces cerevisiae XQ-05 were 30.00 U/L after fermentation.For β-glucosidase,JL-25 showed the highest content of 2110.79 μU/mL on the 3th day,decreased to 752.77 μU/mL on the 5th day,followed by Saccharomyces cerevisiae XQ-05(518.06 μU/mL).In summary,Saccharomyces cerevisiae XQ-05 appared at quickly fermentation speed,strong acid and enzyme production capacity,which is suitable for grape Jiaosu.The growth of Lactobacillus plantarum ACCC 11095 was better than that of other strains in low pH medium.Reducing sugar and soluble solids of Lactobacillus plantarum ACCC 11095 tended to be stable on the 4th day.The pH of ACCC 11095,ATCC 14917 and GDMCC 1.380 was 3.33～3.35 at the end of the 5th day and the total acidity was 11.07～12.74 g/L,which was significantly higher than other strains(p<0.05).After fermentation,GDMCC 1.380 appeared at the highest SOD activity,which was 37.50 U/mL,followed by ATCC 14917.While ACCC 11095 grape Jiaosu appeared at the highestβ-glucosidase activity,which was 400.70 μU/mL.The lactic acid production capacity of ACCC 11095 was 1.2～30 folder higher than that of other strains.All six strains could degrade malic acid and not promote the formation of acetic acid.After 5 days fermentation,the number of viable cells of ACCC 11095 and GDMCC 1.380 in the grape Jiaosu increased to 8.42 and 8.51 log CFU/mL,respectively.In conclusion,Lactobacillus plantarum ACCC 11095 showed high lactic acid production capacity and relatively strong enzyme production capacity,which had greater potential for application of grape Jiaosu.2.The compounds changes in the fermentation process of grape Jiaosu prepared by inoculating yeast,acetic acid bacteria and lactic acid bacteria was investigated,in order to clarify the change law of its characteristic functional factors.Studies have show that the reducing sugar content gradually decreased,and the ethanol concentration increased rapidly from 0 to 7.66%vol during fermentation.The total acid content first rises and then tends to be flat,and the chroma and hue show a similar trend of first decreasing and then increasing.Compared to grape must,the chroma decreased and the hue increased after fermentation.The γ-aminobutyric acid(GABA)content gradually increased during fermentation of grape Jiaosu,reaching 38.95 μg/mL on the 41th day of fermentation.The SOD activity also increased and it was 135.00 U/L at the end of the fermentation.The content of pyruvic acid,citric acid and malic acid began to increase at the first 6 day of fermentation.After inoculation of acetic acid bacteria,the content of acetic acid increased significantly.On the 34th day,the content of acetic acid decreased from 3245.10 to 2760.37 mg/L.malic acid content gradually decreased and the lactic acid content increased to 102.09 mg/L.There were significant differences in flavor compounds in the fermentation process of grape Jiaosu(p<0.05).A total of 43 volatile components have been detected,of which alcohols and esters were abundant.3.In-vitro simulated digestion test was used to study the effect of inoculation fermentation on polyphenols and antioxidant activity of grape Jiaosu,in order to clarify the bioavailability of polyphenols.The result showed that the release of phenolic compounds was promoted by inoculated-fermentation.The content of total phenol and flavonoids fluctuated increasingly during fermentation process,and increased 1.16 and 0.83 fold at the end of fermentation.Compared with must,the content of gallic acid,vanillic acid and myricetin were increased by 6.17,4.18 and 0.60 fold.After in-vitro gastrointestinal digestion,five phenolic acid showed higher bioavailability with a range from 39.11%to 57.77%.In terms of flavonoids,myricetin and quercetin showed great bioavailability,which were 35.78%and 42.34%,respectively.The antioxidant activity of grape jiaosu increased as a whole.Compared with must,DPPH and ABTS free radical scavenging capacity increased by 51.45%and 82.23%respectively.In conclusion,the grape jiaosu fermented by co-culture microbiota can increase the concentration of specific phenolic compounds,improve the bioavailability of some polyphenol,and enhance the antioxidant activity. |
PDF Full Text Request