| Fermented sausage is one of the fermented meat products with largest output. Its nutrition, long shelf-life and special flavor make it popular in various regions. However, traditional sausage in our country is confronted with questions like long production period, unstable quality and poor safety. In modern industrial processing, more attention is paid to starter cultures to achieve effective control and ensure stable quality and safety. Currently, the aim of our study is to obtain the predominant strains in the source of traditional fermented meat products and apply them to the processing of fermented meat products. In this thesis, the predominant lactic acid bacteria were sieved out from the traditional Sichuan sausage. These lactic acid bacteria were mixed with staphylococcus which was used during the processing of Sichuan sausage. The major research content and experimental results are as follows:1. A total of126strains of lactic acid bacteria (LAB) were isolated from Sichuan natural fermented sausages, and two strains of Lactobacillns (L1, L2) and one strain of Streptococcus lactis (P3) were selected by transparent ring method and fermention capacity. Their important fermentation characteristics were identified by acid-producing, salt-tolerating and nitrite-tolerating experiments respectively. Results indicated that there were some differences in growing curve and the ability of producing acid between the lactobacillus and the streptococcus lactis. Three strains of lactic acid bacteria exhibited excellent tolerance to salt and nitrite, no degradation ability to protein and fat, and excellent inhibitory effect against Escherichia coli and Staphylococcus aureus. According to biochemical characteristics and16S rRNA sequences, L1, L2, P3were identified to be Lactobacillus plantarum, Lactobacillus plantarum, Pediococcus pentosaceus respectively.2. Taking three strains of lactic acid bacteria(L1:Lactobacillus plantarum, L2: Lactobacillus plantarum, P3:Pediococcus pentosaceus), which acquired from Sichuan sausage of natural fermentation as the object of study, measuring the24h growth curve and pH value change, salt tolerance and resistance to nitrite, optimum growth temperature, optimum growth pH and selecting mixed starter culture. Experimental results showed that: The growth rate and pH decline rate of lactobacillus were more quickly than streptococcus lactis. Three strains of lactic acid bacteria can quickly reproduce and quickly reduce the pH value. The optimum growth temperature was30℃, and optimum growth pH was5.5. They were able to withstand a concentration of6%NaCl and the nitrite of150mg/kg. The research results showed that the three strains of lactic acid bacteria acquired from traditional natural fermentation of Sichuan sausage can be used as a good sausage fermentation agent. The L2，P3and Saprophytic staphylococcus can be used in the production of fermented sausage as a mixed fermentation agent.3. The fermentation conditions of artificial fermented sausages were optimized by orthogonal experiment.The best optimum were gained by orthogonal test L9(34). The result showed that, the optimal fermentation process of leavening agents was106cfu/g, temperature of fermentation was24℃, relative humidity was80%and time of fermentation was20-24h.4. The mixture of Lactobacillus plantarum, Pediococcus pentosaceus and Saprophytic staphylococcus were isolated from Sichuan natural fermented sausages, which were used to produce artificial fermented sausages, while using the non-inoculated sausages as a control and detecting the physical, chemical and microbiological indicators of two groups. Results showed that pH of the sausages decreased faster in experimental group than those in control group in the first four days of fermentation(P<0.01). After20days processing, pH of the artificial inoculation group which was4.63was lower than that of control group which was5.11(P<0.01). The thiobarbituric acid value (TBA) was slightly lower, nitrite and total volatile base nitrogen (TVB-N) of the sausages in artificial inoculation group were significantly lower (P<0.01) than those in control group. The amount of free amino acid for the artificial inoculation group increased by21.32%in comparison to the control group, with an increase of38.45%in essential amino-acid. The unsaturated fatty acid of the artificial inoculation group was68.99%, which was greater than the control group. The number of bacterias, Lactobacillus, Staphylococcus counts on two groups tended to coincidence in the end. |
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