Isolation And Identification Of Acid Producing Bacteria From Fermented Soy Whey,and The Process Of Tofu

Soy whey obtained during the process of pressing tofu is a byproduct of the preparation of soybean products,and is used as a raw material fermented with lactic acid bacteria for fermented soy whey(FSW).FSW tofu,rich nutrition,bean flavor,sweet,tender taste,elastic,economical and practical,is the delicious food which most people like to eat.FSW has a long history and has been listed as intangible cultural heritage for the wide prospect of research.In this paper,three aspects of FSW were studied.These were physicochemical index,Physail flora,isolation and identification of dominant bacteria.And further to research the produce acid properties and optimization of the FSW with Lactobacillus plantarum JMC-1,and the process of FSW tofu coagulation.The goal of research is to make the fermented soy whey tofu fits the industrialized production well,and solve the pollution problem of soy whey from tofu processing.The main contents and conclusions of this paper were as follows:1?Determination of the physicochemical indexes and flora.In this experiment,the sample was obtained from FSW tofu workshop.The physicochemical indexes and flora were studied.In FSW,the ash content was 5.61 ±0.22mg/mL,protein content was 4.59±0.27mg/mL,fat content was 4.20± 0.13 mg/mL and the content of soluble solids was 1.22 ±0.01 mg/mL.The different bacteria were classified based on the special culture medium.The results showed that the content of lactic acid bacteria was 11.34± 0.02 log(CFU/mL),the content of yeast was 4.41 ± 0.03 log(CFU/mL),and the Escherichia coli and fungi were not detected.2.Isolation and identification of acid producing bacteria163 strains of bacteria were isolated from naturally fermented soy whey,of which 112 strains of lactic acid bacteria,18 strains of coccus,and 33 strains of yeast.7 strains with good effect of coagulation were obtained by the coagolation effect of soymilk.Among the 7strains,a JMC-1 strain with the strongest acid producing ability was screened by testing pH change and acid production of each strain.Through the identification of physiological and biochemical level and molecular level,JMC-1 strain was confirmed as a plant lactobacillus and closed to L.plantarum strain IMAU80102.At the 16h fermentation with Lactobacillus plantarum JMC-1,its pH value was below 4,a maximum of acid production was 6.99mg/mL and the maximum acid production rate was 0.66mL/h.3?Research on the characteristics of the FSWThe changes in organic acid of Lactobacillus plantarum JMC-1 were detected by HPLC method during fermentation of soy whey.After the separation and identification of organic acid,10 kinds of organic acids were detected.The lactic acid content was the major part and increased to 10486.63mg/L,then the content of acetic acid reached 1894.78mg/L,the total acid content reached 13576.57 mg/L.Using Matlab software to fit the kinetic models of cell growth,product formation,substrate consumption and pH changes in the fermentation process,obtained their respective curve fitting degree were 0.9666,0.9919,0.9769,0.9965.The value of model fit the experimental data better,so it could be regarded as the dynamic model is feasible,fermentation the process model can be used to control the plant lactobacillus JMC-1,so as to improve the product synthesis.4?The coagulation processing of FSW tofuThe process of coagulation was a key step to decide the quality of FSW tofu The experiment was done at three aspects:different concentration of soy milk,different pH values of FSW and soy whey.The evaluation indicators of tofu quality were tofu yield,water holding capacity,TPA,color and sensory evaluation.The results suggested that the FSW tofu would have a better quality when added the FSW to the soy milk until the pH value of soy whey got 5.8.The FSW tofu with bean water 1:6 had a higher yield and better quality than FSW tofu with bean water 1:10.