Studies On Pure Fermenting Pickles And The Volatile Flavor Components

Pickle is a product of vegetables fermented by Lacto-bacteria. It has a long history of 2000 years. The mechanism of the fermentation is complex. Lacto-bacteria can use many kinds of sugars included in vegetables to product acids and its inimitable flavor. Pickle is a valuable food. It has its own use, such as: stimulate the appetite; depressing cholesterin; preventing skin from aging; defending cancer and so on. Nowadays, the pickle fermentation is still operated by hand in household in China. It has disadvantages of low efficiency, small scale, difficult in favor controlling, for example. Now, more and more people pay attention to the health of food. Presence of nitrite makes people keep away from pickles. The objective of this thesis was to study difference in processed white radish by fermentation with Lacto-bacteria and by natural fermentation.The experimental results are summarized as follows.1.Experiments were carried out to investigate physiological characteristics of Bacillus A8, B2 and B4 separated from Pickles sold on the market. It was shown that A8 and B2 were Lac. Curvatus, and B4 was Lac. plantarum.2.Three important parameters of pH, OD and Lactic acid were measured during the fermentation process. It was found that the pH of the pickle juice decreased to 3.5 in 1 ~2 days in the fermentation with Lacto-bacteria, especially of B4, but it needed 3 days to reach the same level in natural fermentation. OD and the total number of the bacteria began to decrease at the second day. Lacto acid content of the pickle juice in the fermentation with Lacto-bacteria kept the same level after 2 days, indicating that fermentation was mature.3.Sensory evaluation was taken in the experimentation. The product fermented by B4 was most accepted because of its good taste.4.Nitrite was examined by nitrosoguanidine measurement. Nitrite content reached to peak earlier in fermentation with low salt concentration than with high salt concentration. The nitrite content increased in 3 days, and decreased after that time inthe fermentation with pure lacto-bacteria and with salt concentrations of 8%. The product had the lower nitrite content in the fermenting by I.acto-bacteria.5.A method based on headspace solid phase microextraction (SPME) was used for analyzing the volatile compounds of the pickles. After absorption and desorbing by SPME, volatile compounds were separated and isolated in the GC-Trance Mass system. Although the varieties of volatile components were fewer, the amounts of some volatile components in the fermentation with lacto-bacteria were more than that by natural fermentation.6.A HPLC was used to analyze organic acid, and an amino acid Analyzer was used to investigate amino acid contained in the pickles. The organic acid content of the products was 18.5 mg/mL at least. There were more than 16 kinds of amino acids in the radish pickles. The content of amino acids increased more than 190 percent, reaching to 8.6mg/ml, compared with 2.95 mg/ml before fermentation.