Ham Fermenting Bacteria And Ham Quality Relationship

There were a lot of bacterium resources in the naturally fermented food, from which we can select starter cultures with excellent characteristics for fermented meat products. In this paper, we analyzed the microbial composition of the traditional fermented meat--Rugao ham, and also carried out isolation, purification, characterization and application of the microbial system.In the constitutes of naturally fermented ham, Cocci,bacillus,yeasts and molds are the mainly microbiology. During the first period of fermentation, there are a lot of bacterium and yeasts in the center of ham, with a ratio of 1.7:1, and within the bacterium, cocci is primary comparing to bacillus, with a ratio of 3.9 :1; but in the anaphase of fermentation the ratio of bacteria and yeasts got to 165:1. Besides, there are also molds growing on the surface of ham during the fermentation process, but none was examined inside.We selected favorable microbes according to the capability of producing flavor and aroma through sensory evaluation and GC-MS analysis. From Rugao ham five strains of staphylococci were selected out, which were S.epidermidisC₁₄₁,S. auricularis C₁₃₁,C₁₅₅,C₁₅₆,S.xylosus C₂₃₁; two strains of bacillus were Curtobacterium R₂₅₁,Bacillus R₁₃₂; and one strain of yeast was Dabaryomyces Hansenula Y₁₆₃ isolated with MSA medium,5%NaCl medium and YPD medium were used.The biological characteristics of the strains were studied. The results showed that the strains above all had strong to tolerance to salt and nitrite, and C₁₃₁,C₁₄₁,C₂₃₁ were the best ones; C₁₄₁and C₂₃₁ had both proteolytic and liplolytic activity; C₁₃₁ and R₂₅₁ only had liplolytic activity; R₁₃₂ only had proteolytic activity; Y₁₆₃ only had weak proteolytic activity. Their optimal temperature was from 30 to 35℃.We also studied the relationship of those strains cultivated in the stimulated meat soup, and results showed that those strains didn't resist obviously.According to the activity of protease and lipase, one strain was selected out from Rugao ham, which was preliminarily identified as P.chrysogenum. Hemolysis's and animal experimentation showed that all strains were nontoxic. We studied the quality of ham which was fermented respectively by different strains. The quality standards included the amounts of bacteria, staphylococci and yeast, pH, free amino acid and trimethylamine-N .Results showed that all strains could obviously affect pH, the content of free amino acid and trimethylamine-N. Except R₂₅₁ and C₁₄₁, the other strains could increase the content of free amino acid; Y₁₆₃ could reduce pH; R₁₃₂ could reduce the content of trimethylamine-N. And considering all the factors , C₁₃₁,Y₁₆₃ and R₁₃₂ were proved to be appropriate.To make certain the optimal proportion of C₁₃₁,Y₁₆₃ and R₁₃₂, orthogonal test L9(3)4 was conducted, with pH, the content of free amino acid and trimethylamine-N as standards. The results showed that, when fermented at 30～35℃and inoculated P.chrysogenus on the surface and the proportion of C₁₃₁,Y₁₆₃ and R₁₃₂ was 3:3:2, the quality of ham was the best with the highest contents of free amino acid and acidity and the lowest content of trimethylamine-N.