Isolation Of Lactic Acid Bacteria From Naturally Fermented Sauerkraut And Evaluation Of Fermentation Characteristics

Sauerkraut is a kind of traditional fermented food originating from northeast China and.It has a long history of development.It is popular among the public because of its rich nutrition,sour taste and unique flavor.The principle of making sauerkraut is to produce sour substances and other active metabolites through the metabolism of microorganisms,which giving the vegetables a unique flavor.The traditional natural fermentation mainly depend on the beneficial microorganisms that naturally present on the vegetable surface.In the current,many factories still adopt the natural fermentation method,which has shortcomings such as long production cycle and unstable product quality;while foreign countries have used sauerkraut starter for large-scale production and have achieved good results.Based on this,the aim of this paper was to isolate dominant strains from the natural fermented sauerkraut to develop sauerkraut starter.The main research contents and results are as follows:1.Seventy-three strains were isolated from natural fermented sauerkraut,fermented miso and Kefir.Ninteen strains were identified as lactic acid bacteria by Gram staining,physiological and biochemical tests.Based on the acid production rate,acid production,nitrite degradation ability and bacteriostatic ability,19 strains of lactic acid bacteria were screened with fermentation,and 5 strains were screened with better fermentation performance.2.The five strains were identified by 16 S rDNA gene sequencing,and which were identified as three Lactobacillus plantarum strains.The homology of strain S3 was 99% consist with the Lactobacillus plantarum strain K25.The homology of S5,S11 and S18 were 100% consist with Lactobacillus plantarum strain KC28.And the homology of strain S19 was 100% consist with Lactobacillus sp.D1501.3.The strains were freeze-dried by vacuum freeze-drying technology.And 0.2% ratio weight of cabbage was added and 20 days of fermentation.The sauerkraut fermented with the No.S3 strain has the highest sensory score,and the pH value was lower than other samples during the fermentation,as well as its fermentation speed.In addition,the total acid content is 5.84g/100 g.It is interesting that the nitrite concentration in the 5 samples were all under the safe edible value.4.The varieties and concentrations of organic acids in sauerkraut samples were detected with HPLC.The results showed that NO.S3 sample has the highest concentration of lactic acid(25.65mg/g),and rich in succinic acid(9.38mg/g),which contribute its obvious umami and soft acidity.5.Through the analysis of the volatile components of the sauerkraut samples,a total of eleven volatile compounds were detected(esters,isothiocyanates,alcohols,ketones,aldehydes,hydrocarbons,Ethers,acids,nitriles,sulfides and heterocyclic),and 34 volatile components were detected in sample No.S3,and more than 20 volatile compounts were detected in the other four samples,which can expain the more abundant flavor of NO.S3.Based on the above results,NO.S3 is the best lactic acid bacteria strain as a sauerkraut starter.