Screening And Application Of Lactobacillus For Cabbage Fermentation

Lactobacillus is a very important group of fungi in fermented vegetables, which has important influence on the flavor and quality of fermented products. It is very necessary to screen the fine Lactobacillus from fermented vegetables and yogurt which can be applied in fermented cabbage.This experiment adopts the natural fermented cabbage juice for screening source, because the natural fermented cabbage juice is rich in a variety of lactic acid bacteria, some of which also has a good capacity of producing acid and antibacterial effect.This experiment has get two good strains by means of the isolation, screening, identification and applications of lactic acid bacteria in fermented cabbage juice. The good strains screened out through these experiments have provide a theoretical basis for the development of lactic acid bacteria starter and its application in food.This experiment has divided into five parts in total:1.The experiment have isolated 6 strains from the natural fermented cabbage juice by using the improved MRS culture medium, all of which can produce acid. The 6 strains have been determined as gram positive bacillus by gram staining and using microscopy and negative in the catalase experiment, so with the colony appearance morphology they’re preliminarily concluded to be Lactobacillus genus.2.The 6 strains of Lactobacillus isolated from fermented cabbage juice and 9 strains of lactobacillus saved in lab have beed used in the experiment of producing acid.Respectively, the pH of MRS fermentation liquor have been determined in the fermentation time of 0h, 8h, 16 h and 24 h. 2 strains have been selected which can produced the most yield of acid,the numbers of which are M1-4 and M39. The broad-spectrum antibacterial effect of the 11 strains have been obtained by Oxford cup AGAR diffusion experiments, in which pathogenic bacteria of escherichia coli, staphylococcus aureus, salmonella and liszt were indicator bacteria. 2 strains have been selected which have the best antibacterial effect,the numbers of which are M1-4 and M39. Strain M39 kept in lab is known as Lactobacillus plantarum M39.3.Strain M1-4 have been identified as Lactobacillus casei M1-4 by means of 16 s rDNA sequence analysis experiment..4.Cabbage inoculated strain of M1-4 and M39 fermented in 30℃ and 37℃, the pH of fermented juice have been determined in fermentation.It is found that the pH of fermented cabbage juice in 37℃ drops more quickly than in 30℃ and the final acidity lower than that in 30℃.In the same temperature, the pH of fermented cabbage juice with inoculation drops more faster than that without inoculation.5.Through the sensory evaluation of fermented cabbage products, it’s found that fermented cabbage inoculated strain of M1-4 and M39 has good color, flavor and high quality, but fermented cabbage without inoculation has rotted.The quality of 30℃ fermented cabbage is higher than 37℃ fermented cabbage.The volatile components of fermented cabbage(inoculated Lactobacillus) samples were analyzed by using top solid-phase extraction method and gc/ms chromatograph. 19 and 12 kinds of volatile substances have respectively isolated from the fermented cabbage samples inoculated strain of M1-4 in 30℃and 37℃; 20 kinds of volatile substances have isolated from the fermented cabbage samples inoculated strain of M39 in both 30℃ and 37℃. The major flavor substances of cabbage fermented with strains of M1-4 or M39 both are hexanaphthene siloxane, ten three methyl siloxane ring five and six ring siloxane.