Study On The Diversity And Mechanism Of Dry Fermented Sausages Microbial And Their Key Enzymes During Fermentation Process

Dry suasage is a kind of important Chinese traditional meat product, which is very popular in northern China, especially in the Northeast. But the traditional dry suasages production technology is not mature, it can’t meet the requirements of modern industrial production. Therefore, this study concentrated on microbial diversity and effects of lipase and protease during the dry sausages fermentation process, hoping to screencan some microorganisms with good fermentation characteristics and to figure out the role of enzymes during the fermentation process, and then laying a foundation for the industrial production of dry suasage.We isolated microorganisms using the plate method. and then separated 17 bacteria using the protease activity screening medium and lipase activity screening medium. There were seven and six bacteria which has the optimum growth temperature condition is 20℃ and 42℃ respectively. 15 kinds of bacteria had optimum growth p H condition is 5-7. Using the kit extracted total microbial DNA and then performed PCR amplification. The amplified products were sequenced by biotech companies. Comparing the sequencing results to Blast, we found dry suasage microbes including fungi and bacteria. There are two type fungi: Kodamaea ohmeri and Candida as well as some bacteria: Bacillus subtilis, Bacillus amyloliquefaciens, Swine manure bacterium, Endophytic bacterium, Staphylococcus saprophyticus, Bacillus pumilus and Serratia sp etc.MRS-2 protease enzyme activity was 21.27±1.81U/m L, which was the highest. On contrary, PDA-7 protease enzyme activity was 1.10±0.97 U/m L, ranked the last place in 17 bacterial; MRS-3 had the highest fat hydrolase activity, which was 106.58±3.00 U/m L, PDA-8 had the lowest, which was 6.58±1.90 U/m L. YPD-5 synthetic ester lipase activity was 1.34±0.74 U/m L, which was the highest. Extraction crude enzyme solution of strains to determination of fat hydrolase, synthetic ester lipase and protease enzyme activity under different temperatures and p H values conditions. The optimum reaction temperature of protease was 20℃, 25℃, 30℃, 37℃, 42℃ in 5, 3, 4, 1, 4 strains bacteria respectively. Protease optimum reaction p H values were p H = 4-6, p H = 6-7, p H = 8-9, p H = 9-10, p H = 11-12 among 2, 2, 2, 3, 8 strains bacteria, respectively; The optimum reaction temperature of fat hydrolase was 20℃, 30℃, 37℃, 42℃ in 5, 5, 4, 3 strains bacteria, respectively. The optimum reaction p H values of fat hydrolase was p H = 6-7, p H = 8-9, p H = 9-10, p H = 11-12 in 4, 4, 4, 11 strains bacteria, respectively; The optimum reaction temperature of synthesis ester lipase was 20℃, 25℃, 30℃, 37℃, 42℃ in 4, 2, 6, 4, 1 strains bacteria respectively. The optimum reaction p H value for synthesis ester lipase was p H = 6-7, p H = 8-9, p H = 9-10, p H = 11-12 in 3, 5, 5, 4, respectively. The strains protein content measured by the BCA kit found that all strains could produce proteins. YPD-3 had the highest protein content, which was 2992.46 ± 538.48 μg/m L, and PDA-7 was 960.94 ± 42.65μg/m L, which ranked the last place.Using texture analyzer measured five parameters of dry fermented suasage. They were hardness, adhesiveness, springiness, chewiness and resilience. The results showed that the hardness and adhesiveness of the experimental group were significantly higher than the control group. The resilience and springiness of experimental group were smaller than the control group. As for the chewiness, there was no significant difference between the experimental group and control group. The sensory evaluation of fermented dry fermented suasage showed that the fermented dry fermented suasage 3 days and 10 days got significantly higher score than control group, while the dried cured salami fermented 6 days was lower than control group. The p H values of dry fermented suasage were below to 7 in each period. The p H value decreased from 5.74 to 4.8 and then stabilized. The yield of dry suasage decreased with the fermentation time. The yield of dry suasage fermented 3 days, 6 days and 10 days was 60%, 48% and 44%, respectively.