Effects Of Inoculation Of Lactobacillus And Salt On Sauerkraut Fermentation In Northeast China

Fermented food is a kind of food made by microorganisms or enzyme action on fresh materials.Lactic-acid fermented food,one of fermented food,includes yogurt,kimichi,sauerkraut and so on.Because of various flavors and probiotics in end product,they have the effects of scavenging intestine,regulating the balance of intestinal flora,preventing suffered a cerebral hemorrhage and fighting against arteriosclerosis.Therefore,they are very popular with people.The researches on lactic acid fermented food will aid to screen more probiotics from fermentation system and accelerate the industrial development of related food production.When preparing traditional fermented food,people often use high-salt fermenting to inhibit the growth of miscellaneous bacteria.However,long-term high salt intake could increase the risk of hypertension and diabetes.Therefore,it's necessary and important to develop low-salt fermented food.Sauerkraut is a kind of traditional fermented food in China.People use a lot of salt when making sauerkraut.According to the previous reports on vegetable fermentation,inoculation could reduce salt concentration.But relevant data is lack about sauerkraut in Northeast China.Above all,in this study,we firstly screened inoculated Lactobacillus strains.After obtaining the dominant Lactobacillus strain,we set different salt concentrations to investigate the feasibility of produce low-salt suan-cai.The main results were as follows:(1)To Screen of Lactobacillus oligofermentans strains,L oligofermentans SH-Y15 was used as the control,which was separated from sauerkraut and having a higher degrading ability to nitrite.The strain LO10 was screened.Degrading ability to nitrite and antimicrobial activity of LO10 were better than SH-Y15 significantly.The cultural characteristics of four Lactobacillus strains often isolated from sauerkraut showed that L curvatus grown most rapidly,L.plantarum had the maximum growth,the most acid production.When in low temperature,L.curvatus and L.plantarum finally produced twice as lactic acid content as L.brevis and L.oligofermentans in glucose MRS media.While in xylose MRS media,the final number of moles of lactic acid to acetic acid of L.brevis and L.oligofermentans was close to 1:1.The two strains produce 1.56 times as titratable acidity content as producing in glucose substrate.(2)Inoculation accelerated the decrease of pH and the increase of lactic acid production,raised the number of lactic acid bacteria at the initial fermentation,and increased the relative abundance of Lactobacillus and reduced the relative abundance of Enterobacteriaceae and Pseudomonas at the end of fermentation.This result indicated that inoculation treatments could shorten the fermentation progress significantly and improve the product quality and microbiological safety of fermented products.At the initial fermentation,the fermented system of sauerkraut inoculated L curvatus or L.oligofermentans has the highest relative abundance of Lactobacillus.At the end of fermentation,the fermented system of sauerkraut inoculated L curvatus or L.plantarum has the highest lactic acid content Combined with the result of biochemical parameters and microbial composition,L.curvatus inoculation could control the fermentation progress better at the initial fermentation,and obtained the final products with more lactic acid.(3)Different salt concentrations were set to study the feasibility of low-salt fermentation.At the 3 days of fermentation,the pH values of all treatments were below 4,and the contents of nitrite of salted treatments were below to 20 mg/kg.The contents of final titratable acidity and lactic acid of three treatments including of no salt addition,0.5%and 1%salt concentration addition,were higher than the treatments of 2%-5%salt concentration significantly(p<0.05).The number the lactic acid bacteria in the treatments with more salt addition,decreased more faster during the fermentation progress.Wth the increase of salt in treatments,the relative abundance of Lactobacillus increased,and the relative abundance of Lactococcus,Leuconostoc,Chryseobacterium.Pectobacterium,Pseudomonas and Enterobacteriaceae decreased.With the result of sensory evaluation,it is possible to use a combination of inoculation and 0.5%salt concentration to obtain the products with high acid content,microbiological safety and sensible quality.