The Study On Spontaneous Fermentation And Pure Inoculation Fermentation

Chinese sauerkraut is one of the typical representatives of Chinese traditional fermented food. The principle of fermentation is complex. The microbes from natural environment are considered to use nutrients in raw materials to produce acid and its special flavor. Our study can provide a useful basis for further studies of the development of compound starter cultures, control of the fermentation process as well as the metabolic mechanism of multi-strain synergistic fermentation in traditional sauerkraut production.In our experimental system, four of the lactic acid bacteria (LAB) strains, namely, Lactobacillus plantarun, Lactobacillus casei, Lactobacillus zeae, Leuconostoc mesenteroides subsp. mesenteroides were analysised, which may occur in fresh or fermented as starter cultures for Chinese sauerkraut. The four of lactic acid bacteria were isolated and had been identified by other members in our team.During the fermentation, the water and the cabbage were took out as samples aseptically every12h for the measurements of pH, nitrite content and analysis of HPLC. Some compounds and changes were measured cabbage fermentation. Chinese sauerkraut and inoculated products were compared by instrumental analysis.The conclusions were as follows:The separation of samples contained lactic acid, glucose, malic acid, citric acid,succinic acid,fructose, ethyl alcohol and acetic acid. lactic acid is the most typical product which changes obviously with the time, and ethyl alcohol was found during Chinese sauerkraut and cabbage fermentation isolated Leuconostoc mesenteroides subsp. Mesenteroides. The four kinds of LAB strain showed similar glucose consumption. Of the four kinds sauerkraut evaluated, L. Plantarum showed the highest concentration of lactic acid at the end of cabbage fermentation.The four kinds of LAB strain showed similar the counts of LAB and pH during cabbage fermentation. The counts of LAB of cabbage fermentation inoculated with pure starters were significantly higher than that of spontaneous fermentation during the whole fermentation process.During spontaneous fermentation, nitrite content reached the nitrite peak and decreased thereafter, while only small fluctuations in nitrite concentration were observed for cabbages inoculated with starter cultures. In the test of nitrite degradation,the degradation rate reached more than99%, which has shown that LAB looks promising as a starter culture for sauerkraut fermentation.Volatile compounds were separated and isolated in the GC-Trance Mass system. Although the varieties of volatile components were not comprehensive, the components are saved as can as possible. The amounts and varieties of some volatile components in the fermentation with LAB were similar, but the concent is different.