Study On The Dynamic Change Law And Fermentation Performance Of Yeasts During The Fermentation Process Of Traditional Sichuan Pickle

Classical Sichuan pickle is a kind of food made from fresh vegetables soaked in brine. It is fermented vegetable product made through anaerobic fermentation, being uniquely fresh, fragrant, crisp, tender, acid and cool. The brine (commonly known as "laoyanshui") is usually repeatedly used. This study uses3kinds of brine,40%of which is used brine and60%of which is boiled water, to respectively soak green vegetables, radish and cabbage. Based on the research of dynamic change law and fermentation properties of the saccharomycetes during the fermentation process of traditional Sichuan pickle, the main results are as follows:1.5suspected strains of yeasts could be isolated and purified from the fermentation process. Identified by Sequence analysis of D1/D2region of26S rDNA, four of the strains were Kazachstania exigua and the last one Pichia membranefaciens.2. Experimental choosed preferably YPD medium as medium for counting yeasts. And the article studied systematically the dynamic change law of the yesats existing in traditional Sichuan pickle. The result showed:2kinds of yeasts both had been existing in early period of fermentation process. The number is appoximately105CFU/mL at initial time. In fermental liquid containing geen vegetables, the number of2kinds of yeasts had been reducing, and could not be detected after5d; In fermental liquid containing carrot, the number of2kinds of yeasts had been increasing to mixmum after2d, then decreasing, and could not be detected after5d; In fermental liquid containing cabbage, the number of Kazachstania exigua was decreaseing after the first increaseing in trends, and Pichia membranefaciens could not be detected. Synchronous determination of pH in brine indicated that reduction in the number of yeasts were positively correlated with decreased pH value in the brine. Therefore, acidity and the raw material is the important factors which infulunce on the dynamic changes of yeasts during the fermentation process.3. The article researched fermentation performance of the two strains yeasts isolated from old brine Through the fermentation experiments and simulation fermentation experiments. The fermentation experiments showed that Kazachstania exigua produced less gas and alcohol, not producing fiim. The ability to use of reducing sugar is strong, and can produce lipid. It is more able to adapt to high acid and high salt environment than Pichia membranefaciens. Pichia membranefaciens produced more gas and less fiim, not producing alcohol. The ability to use of reducing sugar is weak. Pichia membranefaciens would produce more acid while fermentation with the lactobacillus. Therefore, fermentation performance of Kazachstania exigua is better than Pichia membranefaciens.The experiment results lay a foundation for further studying the law dynamic change and mechanism of action of yeasts in classical Sichuan kimchi, and offered reference value for developing yeast-Lactic acid bacteria mixed fermentation and industrial production.