The Study On The Microorganisms And Its Metabolic Characteristic During Nature Fermentation And Starter Fermentation Of Chinese

Sauerkraut is a typical traditional fermented food in China, which is delicious, crisp, healthy and contains much nutrients.In this paper, according to the formula of Sichuan sauerkraut, the changes and metabolic characteristic of microorganisms during sauerkraut fermentation were investigated using nature fermentation sauerkraut and starter fermentation sauerkraut as objects. During these fermentations, pH, microorganisms(lactic acid bacteria, yeast, mould and acetic bacteria), substrates(sucrose, glucose, fructose, critic acid and malic acid) and products(lactic acid, acetic acid and ethanol) as the indicators were monitored. pH in the brine was directly detected by pH meter; microorganisms were analyzed by selective medium; the changes in the concentrations of substrates and products were analyzed by high performance liquid chromatography. The results were given as follows:1) The studying on the microorganisms and metabolic characteristic of nature fermented sauerkraut were shown. Laboratory scale fermentations of Chinese sauerkraut were performed to investigate the changes in microorganisms, the pH of the brine, the substrates and the metabolic products. The main microorganisms were monitored using selective agar medium. The substrates and the metabolic products were analyzed by high performance liquid chromatography. The results evidenced that the main microorganisms included lactic acid bacteria, acetic bacteria, saccharomycetes and mycete. The pH was reduced from 5.7 to 3.2 after 7 days of fermentation. The utilization of sucrose during the fermentation was strong, as indicated by a reduction from 74.4 to 18.4 mmol/L. However, glucose and fructose were hardly metabolized by the cells and their final concentration were 28.1 mmol/L and 23.2 mmol/L, respectively. Critic acid and malic acid were easily metabolized during the fermentation and their maximum concentrations,(3.4 and 8.9 mmol/L, respectively) were observed after 24 and 12 h of fermentation followed by a decline until reaching a plateau. As the major metabolic product, lactic acid was steadily increased from 5.6 to 149.6 mmol/L during the fermentation; moreover, the levels of ethanol and acetic acid increased in the early stage of the fermentation process.2) The studying on the microorganisms and metabolic characteristic of starter fermented sauerkraut were shown. Inoculation fermentation of traditional Chinese Sauerkraut include Stater Culture Fermentation and co-metabolism of two strains fermentation in China sauerkraut.The Fermentation stains mainly include: Leuconostoc bacteria, Lactobacillus plantarum, Lactobacillus casei and Lactobacillus zeae. In the stater culture fermentations, although Leu.mesenteroides started the sauerkraut faster than the other three species, PH has obviously decline in the early stage,but final pH value of Leu.mesenteroides was highest while other three strains was about 3.2. Changes in microbiological during fermentation about each strains, lactic acid bacteria showed rapid growth to a maximum value after 1 day. Changes in the metabolism of substrate, four LAB showed the best utilization in sucrose, glucose and fructose. Leu.mesenteroides showed the highest utilization in sucrose, however other three strains of Lactobacillus was superior to that of Leu.mesenteroides. Citric was better utilized throughout three strains, while Leu.mesenteroides didn’t show that. Malic acid was metabolized by these four strains. Leu.mesenteroides produced quickly and more lactic acid in early fermentation. Compared with the other stains, they produced lactic acid slowly. In the end, they produced lactic acid were higher than that produced by Leu.mesenteroides. There is only Leuconostoc mesenteroides has significantly increased during fermentation of traditional Chinese Sauerkraut. During the co-metabolism of two strains fermentation in China sauerkraut, Combination includes Leuconostoc mesenteroides and Lactobacillus plantarum, Leuconostoc mesenteroides and Lactobacillus casei, Leuconostoc mesenteroides and Lactobacilluszeae. During these Combination fermentation, pH value was rapid decline at early stage and Dropped to 3.2 till the end. Leuconostoc mesenteroides showed rapid growth at early stage then continuous decline and we didn’t find them after 2.5 days. Changes in the metabolism of substrate, all combination of LAB showed the best utilization in sucrose, glucose and citric and malic acid. Fructose was only utilized Stablity throughout combination of Leuconostoc mesenteroides and Lactobacilluszeae. In the three groups, Lactic and acetic was significant increased.