Isolation, identification of dominant spoilage bacteria and measurement of spoilage characteristics in dried beancurd
In order to study the spoilage mechanism of vacuum-packed dried beancurd, thereby offer reference to extend the shelf-life of dried beancurd. The dominant spoilage bacteria in spoiled dried beancurd were isolated. These isolates were identified basing on the morphological, physiological and biochemical characteristics and 16S rRNA sequence analysis. In order to explore the spoilage characteristics of dominant spoilage bacteria, they were inoculated into aseptically vacuum-packed dried beancurd and cultured at 37 ℃ for 20 d. The results showed that one dominant spoilage bacteria strain was screened out and identified as bacillus subtilis. Some physical parameters of spoiled dried beancurd inoculated with B. subtilis, such as hardness, springiness and cohesiveness, were less than previous dried beancurd. Some chemical contents associated with spoilage were changed greatly. The content of amino acid nitrogen increased from 0.037% to 0.129%, total volatile basic nitrogen(TVB-N) content increased from 5.63 mg/100 g to 33.01 mg/100 g, and the content of total acid(as lactic acid) increased from 0.09% to 0.544%.