Screening And Application Of Excellent Yeast In Jinzhou Side Dish

Jinzhou pickles is one of the specialty foods in Jinzhou City,Liaoning Province,China.Because of its unique flavor and nutritional value,it is highly praised by domestic and foreign consumers.Jinzhou pickles are often produced using natural fermentation methods and it is rich in a large number of probiotic strains with good growth characteristics,but due to its natural fermentation production mode,its microbial flora is greatly affected by the environment,and the flavor quality and safety cannot be guaranteed.In order to overcome the shortcomings of Jinzhou pickles being restricted by the environment,to achieve industrialized large-scale production,it must be changed from natural fermentation to artificial fermentation.Therefore,it is particularly important to screen out high-quality probiotic fermentation agents.Yeast is one of the dominant bacteria in Jinzhou pickles and plays an irreplaceable role in the fermentation process of Jinzhou pickles.In the fermentation process of vegetables,yeast can use the sugar in vegetables to produce ethanol,which provides mellow flavor for fermented vegetables.Ethanol can also be combined with organic acids to form ester aromatic substances,thereby improving the flavor of fermented vegetables.Lactic acid bacteria and yeast all play a vital role in the fermentation of Jinzhou pickles.However,the separation and screening of dominant bacteria in Jinzhou pickles is mainly concentrated on lactic acid bacteria,the yeast which can give its unique flavor is neglected.This study mainly took 44 varieties of Jinzhou pickles in four regions of jinzhou as samples,separation,screening and identification of high quality yeast in samples,Using fermented pickle as a case,the selected high quality yeast and lactic acid bacteria with good fermentation characteristics(separated from Jinzhou pickles,laboratory preservation)were applied to the production of pickles,and the fermentation conditions were optimized,It is expected to provide theoretical basis for the excavation of excellent yeast and the development of mixed starter.The following results were obtained:Twenty strains of yeast were isolated from 44 samples of Jinzhou pickles.Preliminary screening of isolated yeast by acid resistance,salt tolerance,bile salt resistance,gas production,calving,acid production,alcohol production,aroma production and bacteriostatic test.Yeast strains HG2,HD3,LJ1,SJ4 and SJ5 were found to exhibit excellent properties such as acid resistance,salt tolerance,bile salt resistance,no gas production,no pupa production,alcohol production,aroma production,acid production and bacteriostatic action.The 5 selected strains of yeast to carry out the re-screening by using the fermentation characteristics test such as sugar capacity,flavor-producing ability,protein-breaking ability,and acid-producing ability.Finally,the strains HD3 and SJ4 were screened to have excellentfermentation characteristics.After morphological identification,physiological and biochemical test identification and26 S r DNA molecular identification,the strain HD3 was Pichia fermentants,and the strain SJ4 was Torulaspora delbrueckii.Taking pickle fermentation as an actual case,using sensory scoring method,the three strains of Pichia fermentants HD3,Torulaspora delbrueckii SJ4 and Lactobacillus plantarum LC44(laboratory preservation,screening from Jinzhou pickles)were used as test strains for mixed fermentation.The dominant flora of the agent is screened and optimized for optimal strain ratio.The results showed that the sensory scores of fermented pickle were the highest(89.67 points)when the three strains were used together,and the sensory quality of the pickle produced at the ratio of(3:1:3)was the best(92.27 points),through single factor test and response.The optimal inoculation quantity,fermentation temperature and fermentation time of pickle production were optimized by single factor test and response surface analysis.The optimal fermentation conditions for kimchi production were 2.9% inoculum,fermentation temperature 29.6?,and fermentation time 100 h.The sensory score of kimchi produced under this condition was the highest(94.87 points).