Screening,identification And Influence On Histidine Decarboxylase Gene Expression Of Histamine Degrading Bacteriums In Sichuan-Style Sausage

The histamine degrading strains which were used as sausage starter culture were screened from 20 Sichuan-style sausage samples that were used as raw materials and then identified.The product quality,dynamic changes of histamine content and microecosystem,the relative gene expression of histidine decarboxylase?HDC?,and the relative index of protein degradation in control group and inoculating group were analyzed.The main results and conclusions were as follows:1.A total of 3 strains,which were numbered 19,41,46 and could both meet the meat fermented requirements and more effectively degrade the histamine content,were screened from Sichuan-style sausages and were identified as Lactobacillus plantarum,Pediococcus pentosaceus and Weissella cibaria,respectively.All the three strains showed good growing and acid producing ability,and could tolerate low temperature,low pH,60 g/L NaCl and 150mg/kg NaNO₂,while could not mutually inhibit each other.Meanwhile,the mixed starter culture showed better ability to inhibit the growth of histamine producing strains than a single strain.2.The average sensory scores and whole acceptability of control group and inoculating group were 65.07 and 78.57,75.14 and 83.14,respectively.Compared to control group,many aspects of the quality besides color and texture of inoculating group had been obviously improved.It could be effectively distinguished from control group to inoculating group by electronic nose while could not by electronic tongue.3.During the whole process of ripening,the histamine content in control group and inoculating group were both continually increasing,and it was lower than control group from the beginning to the end.The rapid accumulation of histamine in Sichuan-style sausages mainly occurred in the mid and later stage of ripening.At the end of ripening,the histamine content decreased 30.27%comparing inoculating group?46.56 mg/kg?to control group?66.77 mg/kg?and showed a significant difference?P<0.05?.4.During the whole process of ripening,except for lactic acid count,the total bacteria,staphylococcus count,enterobacterium count,and yeast and mould count of inoculating group were all lower than control group.The PCR-DGGE profiles showed that there were variety of bacterium species with a lower content in raw meat materials,and Pediococcus pentosaceus,Lactobacillus plantarum,Weissella and Staphylococcus were gradually becoming the predominant bacteriums in two groups during ripening.Furthermore,Enterobacter aerogenes and Citrobacter freundii,which belonged to Enterobacteriaceae,were the coding HDC gene predominant bacteriums in Sichuan-Style sausages.In addition,a total of 197 kinds of microorganisms in genus level were identified by high-throughput sequencing technique,in which there were 35 kinds of bacteriums coding HDC gene.In most ten abundance,however,there were 5 coding HDC gene,including Citrobacter,Acinetobacter,Staphylococcus,Lactobacillus and Klebsiella.5.The relative HDC gene expression data had different changing tendency in two groups of Sichuan-style sausages.At the early and mid stage?0¹4 d?,the relative HDC gene expression data in inoculating group was lower than control group,but higher at the later stage?18³0 d?.The relative HDC gene expression data depended on the pH of sausages,the temperature of processing and the content of enterobacterium.6.The changes of total nitrogen in two groups were the same.And that TVB-N content in dry basis in inoculating group?21.879 mg/100 g?were significant lower than control group?30.375 mg/100 g?at 30th day indicated that the free amino acid in inoculating group suffered less damage than control group and produced less ammonia and amines with the ripening time went by.Due to the degradation of sarcoplasmic proteins and myofibrillar proteins,more and more low-molecular-weight proteins and amino acids were produced.Meanwhile,more and more precursors of histamine were produced.