Physical, Chemical And Microbial Property Of Sichuan Bacon During Processing And Selection Of Staphylococcus

During recent decades,a large number of studies on the fermented ham and fermented sausage showed that it is a very compex prosess that the flavor formation of fermented meat.During the processing and storage,the many kinds of microorganism combined actions are the important ways which the wild fermentation meat product flavor forms under the natural conditions.Different weather conditions and processing methods will directly affect the micro-ecological structure of the fermented meat,change microflora,and different of the protein and fat decomposition(hydrolysis) in all stages of the processing and storage ultimately affect product quality.Therefore,it is the objective needs that the research on the types,quantities and change of traditional fermented meat microbial that improving processing technology of the traditional fermeted meat and controlling product quality.The changes of bacteria,lactic acid bacteria,Staphylococcus,Micrococcus,yeasts,Enteric bacilli was studied during the processing and storage of Sichuan bacon,the changes of routine physical and chemical indicators such as pH,moisture content,salt,and the changes of lipid oxidation, protein catabolism,were systematic studied.The results showed that during the processing and storage of Sichuan bacon,pH decreased at the curing prophase,the late time of smudging and the ripening.Acids and salt content increased at the curing prophase,while moisture content,Aw and sugar content decreased during processing.TBA value,peroxide value and acidity value all displayed gradually rising trend.Residual nitrite of the ripened product was 9.15 mg/kg.Non-protein nitrogen and amino nitrogen content of the ripened product significantly increased(p＜0.05).Any kinds of free amino acid content of the ripend product increased significantly,and Ala and Val were most aboundent in the products and their contents were 51%of the total free amino acid.A total of 27 kinds of volatile substances were detected in Sichuan bacon,and the main volatile substances were phenols.During the three months of storage,TBA and acidity value increased gradually and peroxide value rise and fall alternately.The total nitrogen content of bacon increased but without significant difference during storage(p＞0.05).Protein hydrolysis mainly occurred in the early stage of storage. Volatile basic nitrogen assumed the trend of escalation during storage,and the storage stands was 40.69 mg/100g after storage of three months.The tipical flavor did not form in the non-ripened bacon and the odorwas mainly the fume smell. Bacon aroma formed after the storage of 15 days,and the good aroma was formed between the storage of 40 days and more than 60 days.The dominant microorganisms in Sichuan bacon were lactic acid bacteria and Staphylococcus. Smoking has significant effect on microflora especially yeast.During the storage,counts of total bacteria maintained at 10~4 cfu/g,Staphylococcus maintained at 10~2 cfu/g,and mold growed slightly.Staphylococcus strains were isolated from traditional Sichuan bacon and screened for their capability of aroma production.A strain named S74 was selected for its ability to leucine metabolism and possession of nitrate reductase.S74 was identified as Staphylococcus xylosus by examining its morphological,physiological and biochemical characteristics.