Study On The Characteristics Of Compound Starter And The Preparation Process Of Bacterial Powder

Based on the current situation of insufficient independent research and development level of meat product fermentation agents in China,it has become a trend to prepare direct injection meat product fermentation agents with high bacterial activity and stable quality to adapt to the development of China’s fermented meat product industry.This experiment used the standard strains of Staphylococcus xylosus,Lactobacillus plantarum X3-2B,and Streptococcus pentosus 37X-3 as the research objects.The optimal composite ratio was determined through preliminary growth characteristics,acid production ability,salt resistance,and sodium nitrite resistance tests to prepare direct injection composite fermentation agent bacterial powder.The freeze-dried protective agent formula was optimized using single factor experiments and response surface methodology,Determine the optimal dosage of various protective agents and the optimal ratio concentration of bacterial sludge to protective agents before freeze-drying.Through storage experiments,the number of viable bacteria and survival rate of meat product fermentation agent bacterial powder were calculated in environments of-20℃,4℃,and 25℃,and the appropriate storage temperature and time were analyzed,providing new ideas and theoretical basis for the industrial and excellent development of meat product direct injection composite bacterial powder fermentation agent.The research results are as follows:First,three target bacteria:standard strain of Staphylococcus xylosus,Lactobacillus plantarum X3-2B and Pediococcus pentosus 37X-3 were tested for antagonism.The test results showed that there was no antagonism effect among the strains.Through live count test on 25 compound proportion strains,12 compound strains with good growth ability were screened out.Acid production,growth performance Through tolerance tests with a certain salt concentration and nitrite concentration,three composite ratios with higher bacterial activity were selected:1﹕1﹕2,1﹕3﹕2,and 2﹕2﹕3.After 20 hours of cultivation,the highest viable bacterial count was 2.59×10~9CFU/g,2.86×10~9CFU/g,2.92×10~9CFU/g.Secondly,the single factor optimization and response surface test of the amount of freeze-dried protective agent were carried out,and the formula of the optimal protective agent was obtained:skim milk powder 17%,trehalose 9%,sodium glutamate 11%;the results showed that the highest freeze-drying survival rate was 70.20%when the mass ratio of sludge to protective agent was 1:1.5.Combined with the previous test,the most suitable ratio of the composite strain was 2:2:3 for Staphylococcus xylosus(standard bacteria),Lactobacillus plantarum X3-2B and Pediococcus pentosaceus 37X-3.The results of scanning electron microscopy showed that the surface pore structure of the freeze-dried powder added with the composite freeze-dried protective agent group was less,and the overall structure was smooth and flat,indicating that the protective agent had a better effect on the cell encapsulation.Finally,the optimal storage temperature for the composite fermentation agent bacterial powder was explored,and the optimal storage conditions were obtained as follows:the fermentation agent bacterial powder was stored in an aluminum foil bag vacuum at-20℃for 30 days,with a higher number of live bacteria and survival rate compared to 4℃and 25℃room temperature environments,with a live bacterial count of 1.47×10~9CFU/g,with a survival rate of 64.82%,indicating that the fermentation agent bacterial powder grows well in a low-temperature environment of-20℃and can be stored for a long time.