Isolation, Screening And Application Of Lactic Acid Bacteria From Fermented Sausages

In the local natural fermented sausages, there are good bacteria resources, which are particularly suitable for meat fermentation. Particularly Lactobacillus, it is the first and the most popular microbial start culture used in fermented sausages. Many Lactobacillus are probiotics to human. In this paper, lactic acid bacteria stains were isolated from two local natural fermented sausages by using fermentation characteristics, process safety and Probiotic Properties as the main indicator. Finaly, the applied research were carried out. The main research contents are as follows:1. Microorganisms and the physical and chemical indicators of two types of natural fermented sausages are studied, and the results show that both fermented sausages have a good bio-safety, and can be used as appropriate sample for strain separation.2. A total of 184 lactobanillus stains were isolated and purified from two types of natural fermented dry sausages after enrichment by capability of endure low acid, capability of endure Bile Salts. After two steps selection, finally, three strains with excellent characteristies were obtained. By preliminary identification,T10703,T10709 were Lactobacillus casei, T20706 was Lactobacillus plantarum. These three lactic acid bacteria all resistanted to the 8% NaCl and 150 mg / Kg nitrite, producted diacetyl, decomposited lactose, did not produce biogenic amine ,H2O2, CO2 , H2S and slime, and they are consistent with the basic requirements for fermented sausage fermentation agent. In addition, they can inhibit Staphylococcus aureus, Escherichia coli, Salmonella, Listeria monocytogenes bacteria.They have a more than 80% survival rate in the high-acid (pH 2.5) situation, and have a good tolerance to 0.3% bile salt. in vivo uptake of human intestinal, naturally play its benefits ,and can be as beneficial fermentation agent for the Health of functional fermented sausage production.3. Mixed performance measurement and selection of fermentation experiments show that the three selected bacteria strains all have strong growth ability, quickly acid forming ability , suitable growth temperature, and do not have lipase and protease activity. They all meet the screening criteria of probiotic lactobanillus stains.there are no antagonism between T10703 and T20706, and can be used as mixed start culture for the production of fermented sausages.4. Use of selected mixed culture products fermented sausages.The best optimum fermentation conditions were gained by orthogonal test L9(34) and optimization.The result showed that, the optimum proportion of Lactobacillus casei T10703 and Lactobacillus plantarum T20706 was 2:1, the viable cell counts was 107cfu/g, temperature of fermentation 22-25℃, and relative humidity was 90-95%, fermented one day; then 16-17℃,relative humidity 85%, fermentation two days.5. Fermented sausages were produced with selected srtains under the best optimum fermentation conditions, and main microbial and physic-chemical changes were studied. lactic acid bacteria in the test group added mixed start cultures was in a dominant position during the entire production process; the addition of mixed lactic acid bacteria culture significantly speed up the droping rate of pH, moisture content, and Aw, and made them down to a lower value,which improved the quality of the product and ensured its biosafety. Besides,the residues of nitrite in test group was lower.Combined with the sensory evaluation, that the selected mixed culture can be used as fermented sausages start culture, but the action effect of Probiotics needs further research.