Optimization Of Technology Of Direct Vat Set Pickles Fermented By Lactic Acid Bacteria

Pickled vegetable is one of the most important traditional fermented food in China,featuring crispy taste and abundant nutrition.It is the precious probiotic food.The production of pickled vegetable in China mainly adopts the natural fermentation process.Under such situation,it is difficult to control the product safety and the product stability is bad,which limits the pickled vegetable industry of China to be stronger.This paper selects and breeds the special probiotic bacterial strain for sound pickled vegetable featuring sound fermenting property and probiotic function.The content and result of study are as follows:(1)Selection of the special pickled vegetable-used probiotic bacterial strain with sound fermenting property.It selected 49 potential lactic acid bacteria from the pickled vegetables in Sichuan and Jiangxi and authenticated them with molecular biology.In accordance with the identification result,16 advantageous heterofermentation and homofermentation lactic acid bacteria were screened out to be further evaluated in terms of their fermenting property.In this way,it got 3 lactic acid bacteria with relatively sound fermenting property.Then,the morphology and molecular biological identification and phylogenetic tree construction were carried out for these 3 lactic acid bacteria.At last,the 3 lactic acid bacteria were confirmed as lactobacillus plantarum,lactococcus lactis and leuconostoc mesenteroides,which are coded as NCU001210,NCU036015 and NCU018046 respectively.(2)Study on the stress tolerance of special probiotic bacterial strain for the fermentation of pickled vegetable:NCU001210,NCU036015 and NCU018046 shall be incubated for 3 h under the condition of pH 3,with the survival rate being over85%.Among them,after being incubated in pH2 for 3 h,NCU001210 still had the viable count of 7.1 Lg(CFU/mL),which indicates the survival rate being up to83.14%;being incubated in the 0.3%cholate for 4 h,3 lactic acid bacteria featured the viable counts of 6.78,6.09 and 6.41 Lg(CFU/mL)respectively,with the survival rate being 79.39%,71.9%and 69.9%;receiving incubation in the simulated gastric fluid and intestinal juice for 3 h and 8h,the survival rate of NCU001210,NCU036015 and NCU018046 was higher than 87%;Receiving incubation for 24 h under the hyperosmosis of 7 g/100mL,the viable counts of NCU001210,NCU036015 and NCU018046 were over 7.5 Lg(CFU/mL).(3)Probiotic characteristics of lactic acid bacteria for pickle fermentation.Taking the DPPH free radical and hydroxyl radical scavenging capacity,reducing power,lipid peroxidation inhibiting ability as indicators,it found out that the DPPH free radical scavenging rates for the whole cell extractive and acellular extractive of the lactobacillus plantarum NCU001210 are 31.34%and 27.02%.The hydroxyl radical scavenging rate for the lactococcus lactis NCU036015 acellular extractive is29.30%.The reducing capacity of the acellular extractive for the leuconostoc mesenteroides NCU018046 is 87.21?mol/L;the fermenting supernatant of the 3lactic acid bacteria has inhibiting effect on 7 common pathogenic bacteria;the adhesiveness of NCU001210,NCU036015 and NCU018046 were studied through Caco-2 cell model.The adhesion abilities of 3 lactic acid bacteria are 3.40,34.1 and11.2 CFU/cell.(4)Direct vat set(DVS)pickled broccoli process study.the single factor experiment confirmed:the optimal cane sugar additive amount was 3%-5%;salt additive amount is 2%-6%;inoculum concentration is 0.01%-0.03%;leavening agent matching is 1:1:1;fermentation temperature is 30?-35?and fermenting duration is40-56 h.The optimal process parameters for the fermentation of DVS pickled broccoli were defined as:the fermenting duration is 48.54 h,fermenting temperature is 32.07?and the inoculum concentration is 0.0256%.(5)Quality analysis of DVS fermenting pickled broccoli.it defined the development trend of the nitrite content in the DVS fermenting pickled broccoli through the measurement of nitrite content in the DVS fermenting pickled broccoli and natural fermenting pickled broccoli.The nitrite content in the pickled broccoli when the fermenting stops was 5.4 mg/kg which is lower than the limit value set by the nation on the nitrite content in the pickled broccoli.Both the DVS fermenting pickled broccoli and natural fermenting pickled broccoli present the trend of increase first and decrease later in terms of the quantity of main pathogenic bacteria.The main pathogenic bacteria in the DVS pickled broccoli disappeared 48h later.The extinction of pathogenic bacteria of natural pickled broccoli was slower than that of DVS pickled broccoli.Among the major metabolic substrates over the fermenting process of DVS pickled broccoli,the cane sugar,glucose,citric acid and malic acid all showed the trend of increase.As the fermentation progressed,the fructose content gradually decreased,and after 56 h,the concentration was 7.7 mg/g.In the main metabolites,both lactic acid and acetic acid showed the rising trend.After experiencing the fermenting of 56 h,Concentration of lactic acid rose from the 2.67mg/g at the beginning to 13.21 mg/g.The volatile flavor analysis of broccoli pickle before and after fermentation showed that the DVS fermentation pickle detected relatively more flavor substances,up to 24 kinds,and its flavor substances contained a large proportion of sulfur compounds and alcohols;The model showed that the DPPH free radical scavenging rate and FRAP reducing ability of pickle under DVS fermentation increased by 32.43%and 39.49%,respectively,and the ABTS~+scavenging ability decreased not significantly(P<0.05).In general,the antioxidant activity of broccoli pickle increased after fermentation,and the antioxidant capacity of pickle was good.DVS fermentation of broccoli pickle is a product that integrates nutrition and health care functions and has great market development potential.