Dynamic Analysis Of Natural Fermented Sour Porridge Flora And The Selection And Application Of Lactic Acid Bacteria

Sour porridge was a traditional fermented grain food in China.It was fermented from milled rice under natural conditions.Through the action of microorganisms in the fermentation broth,the sour porridge gives the sour porridge a sour and smooth taste and rich functional nutrients.It maked the sour porridge in Northwest China.It is loved by people,but the current production of sour porridge is still dominated by small-scale,family workshop-style production,and no industrialized scale production has been formed.The family workshop-style production of sour porridge was made through natural fermentation,which is affected by the region due to natural fermentation.The influence of many factors,such as temperature,temperature and man-made factors,make the quality of sour porridge products unstable and difficult to guarantee,and harmful bacteria may be introduced during the natural fermentation process,which threatens health.Therefore,this study monitors the natural fermentation process of sour porridge.Analyze the composition of the microbial flora in the sour porridge at different fermentation times,and predict the microbial function in the sour porridge through PICTUSt2,and then screen out the lactic acid bacteria with excellent characteristics,and use it for the inoculation fermentation experiment of the sour porridge to optimize the growth conditions and Sour porridge processing technology,and finally analyze the changes in the basic nutrients and physical and chemical indicators of the milled rice before and after fermentation.In order to lay the theoretical foundation and technical reference for the industrial production of sour porridge.1.Exploring the evolution of natural fermented sour porridge microorganisms.After analyzing the microbial composition of sour porridge during different fermentation periods by high-throughput sequencing technology,it was found that as the fermentation time increased,the acidity of sour porridge gradually increased,and the content of some harmful bacteria gradually decreased with the increase of fermentation time,while the content of Lactobacillus The enrichment time is long,and its content gradually increases after about a week.The prediction of the gene function of the microorganisms found that the microorganisms in the porridge at the later stage of fermentation are safer,the pathogenicity is weakened,and the ability to metabolize harmful substances is enhanced.2.Screening and molecular biological identification of lactic acid bacteria with excellent properties.Using the acidity of the fermentation broth and cell density as indicators,a strain with the best growth state and strong acid-producing ability in the rice soup substrate was selected from the natural fermented sour porridge.Through the observation of colony morphology and physiological and biochemical experiments,combined with molecules Biological technology showed that the strain was Lactobacillus paracasei,and named it L a c t o b a c i l l u s p a r a c a s e i SZ02.3.Optimization of fermentation conditions for L.paracasei SZ02.Using the acidity of the fermentation broth as an indicator,a response surface optimization experiment was performed on its fermentation conditions.The optimal fermentation conditions were determined as follows: fermentation time 24 h,inoculum amount 5%,fermentation temperature 35?,glucose as carbon source,carbon source addition amount 2% Under these conditions,the acidity of the fermentation broth is 12.02 °T.4.Optimization of L.paracasei SZ02 pure bacteria fermented sour porridge processing technology.Using sensory scores as indicators,single factor experiments and orthogonal experiments were used to optimize the processing conditions of sour porridge.It was determined that the pure bacteria fermented sour porridge processing conditions were as follows: fermentation time 36 h,fermentation temperature 35?,and cooking time 20 min,Physalis occupies 50% of the water.The sour porridge made under this condition has the best flavor,which is close to the natural fermented sour porridge.