The Quality Of Bagongshan Sufu By Double Mold Fermentation

Sufu is a traditional fermented food with special flavor and taste.It is a secondary processed bean product from tofu co-fermented by microorganisms.The choice of strain determines the fermentation process and quality of sufu.In this paper,the edible Mucoraceae and Rhizopus were firstly used as pure culture fungi in the first stage fermentation of Bagongshan sufu,and the mixed fermentation process was optimized.On this basis,the dynamic changes of the quality of the sufu during the fermentation by Mucoraceae,Rhizopus and their mixed were monitored,including the changes of physical and chemical properties,texture and antioxidant capacity.Finally,the microbial flora characteristics and amino acid nutrients of the three kinds of sufu referred above were compared and analyzed,and the response relationship between microbial flora and amino acid nutrients was explored.The fermentation mechanism of nutrient nutrition change was further clarified.The main findings are as follows:(1)Study on the process of mixed fermented sufu by Mucoraceae and Rhizopus.Using the single factor test and orthogonal test,and selecting protease,lipase and α-amylase as the indicators,the fermentation conditions of mixed fermented sufu by Mucoraceae and Rhizopus were determined: the ratio of inoculum was 1.5:1,inoculum size was 15%,fermentation temperature was 30 °C.The protease,lipase and α-amylase activities at this time were 210 U/mL,68 U/mL,and 186 U/mL,respectively.The sensory evaluation under different fermentation conditions was studied using the nine-point pleasure scale method.The results showed that the different fermentation conditions had significant effects on the sensory evaluation of sufu,especially when the mixed ratio of strains was 1:1,inoculation amount is 10% and the fermentation temperature is 30 °C,the overall acceptability of sufu is 8.1,which is the highest.According to the analysis of correlation between fermentation conditions and quality,the quality of sufu has a significant correlation with the fermentation conditions.(2)Study on physicochemical properties of mixed fermented sufu.The protein content of Mucoraceae,Rhizopus and mixed fermented sufu decreased from about 40% to 26.37%,26.37% and 17.99%.The fat content of Mucoraceae,Rhizopus and mixed fermented sufu were 28.43%,35.12% and 29.34%,respectively.In the salt stage,the fat content decreased,and the mixed fermented sufu with the lowest fat content of 12.02%.The fatty acid contents of Mucoraceae,Rhizopus and mixed fermented sufu were 16.77%,16.37% and 14.58%,respectively.During the fermentation,the content of reducing sugar is generally reduced.The highest content of reducing sugar of mixed fermented sufu was 2.16 g/100 g,and the lowest content was 1.36 g/100 g.The amino acid nitrogen and total acid content of fermented sufu under three conditions increased overall.Among them,the amino acid nitrogen and total acid content of the mixed fermented sufu were 1.49 g/100 g and 1.11 g/100 g,respectively.(3)Study on the texture and antioxidant properties of mixed fermented sufu.During the whole fermentation process,the hardness and the elasticity of the Mucoraceae,Rhizopus and mixed fermented sufu were all decreased,and the adhesion of them was all increased.Such as decreased of the hardness and the elasticity of mixed fermented sufu were the largest,by 43.45% and 70.21%,respectively.While the adhesion of mixed fermented sufu increased by 70.38%,which also was the largest.The analysis of antioxidant results showed that the antioxidant capacity of the mixed fermented sufu was more advantageous than the other two single-fermented sufu.The DPPH free radical scavenging ability of the mixed fermented sufu was significantly enhanced at the end of the fermentation;the ABTS free radical scavenging capacity was 75%,and the reducing ability was increased by 79.8% compared with the tofu.(4)Study on the microbes of the Bagongshan sufu in mixed fermentation.According to the results of PCR amplification and sequencing of the 16 S rDNA gene sequence,there are 194 species shared of Mucoraceae,Rhizopus and mixed fermented sufu,which were,50 species of mixed fermented sufu and Mucoraceae fermented sufu,and 14 species of mixed fermented sufu and Rhizopus fermented sufu.There are 17 species in the Rhizopus fermented sufu and Mucoraceae fermented sufu;By analyzing and comparing the species of sufu under different conditions,it can be seen that the species of mixed fermented sufu is more abundant,and the species of other fermented sufu is relatively single.The results of microbial community characteristic structure analysis showed that the composition of microbial community structure of sufu under three different conditions had great differences.The abundance of Bacillus and Staphylococcus in the mixed fermented sufu was higher than that of Rhizopus fermented sufu.The abundance of Staphylococci and Enterococci in Mucoraceae fermented sufu is higher than that of the mixed fermented sufu.The results of amino acid analysis showed that the essential amino acids of mixed fermented sufu were more abundant than that of Rhizopus and Mucoraceae fermentation.The essential amino acid(EAA)content of mixed fermented sufu reached 123.42 g/kg and the total amino acid content was 43.88%.Through a comprehensive study of fermented sufu by different fungi,we can understand the relationship between the microbial community structure,key population function and nutrient quality of sufu,and the results provide a good reference for the industrial production of sufu.