| In northeast China,pickled cabbage is an indispensable delicacy on the table.People generally pickled pickled cabbage in winter,but naturally fermented pickled cabbage has problems such as different finished products,easy to rot,unpleasant sour smell,high nitrite content and seasonal restrictions,so the market demand of commercial pickled cabbage is expanding.With the development and application of food processing technology,sauerkraut fermentation was transformed from natural fermentation to artificial inoculation of lactic acid bacteria.At present,most commercial pickled cabbage on the market is fermented by single lactic acid bacteria.Compared with natural fermentation,it has less nitrite content,rich vitamin content and better color and lustre.However,single lactic acid bacteria fermentation also has many problems,such as taste,volatile flavor substances are not as rich and mellow as natural fermentation.This project intends to develop a new type of lactic acid bacteria compound starter by screening and identifying the dominant strains in natural fermentation sauerkraut,and combining the screened strains with Lactobacillus plantarum and Lactobacillus paracasei.At the same time,the growth characteristics of the strain were investigated to further determine the optimal fermentation environment.The three strains were fermented sauerkraut by different mixtures,and the quality of sauerkraut by single bacteria fermentation,two-bacteria fermentation,three-bacteria fermentation and natural fermentation was compared,and the best mixture proportion was obtained.Finally,the optimal fermentation conditions were obtained by using nitrite content,pH content as indexes.In this experiment,two strains of lactic acid bacteria DR3-6 and DR5-2 were obtained through preliminary screening and re-screening.Combined with morphological characteristics and molecular biological identification,a phylogenetic tree was constructed,and the two lactic acid bacteria were determined to be Lactobacillus brevis.Explore the biological characteristics of lactic acid bacteria,determine the optimum growth temperature is 35℃,the tolerance limit to sodium chloride is 8%,the salt tolerance of DR3-6 is better,the pH tolerance limit is 3.0,and the degradation rate of nitrite Both reach more than 80%,and the shaking culture method is more conducive to the degradation of nitrite.Construction of a composite bacterial agent: there is no antagonism between the bacterial species and it can inhibit E.coli and S.aureus.The nitrite content in the sauerkraut inoculated with the composite starter is lower than that of the naturally fermented sauerkraut and produces acid faster.The best compounding plan is LP:F:DR3-6=1:1:2;the optimal inoculation amount of sauerkraut starter is 3%～4%,the optimal salt amount is 3%,the initial pH is to the nitrite of sauerkraut The salt content and pH have no significant effect. |
