| In this experiment,67 strains of lactic acid bacteria isolated from traditional cheeses were used as the research object.The curd state and sensory quality were used as indicators for preliminary screening and re-screening,and the dominant strains used in traditional cheese fermentation were screened out according to the curd state and texture characteristics.As an indicator,carry out strain compound fermentation,determine the optimal strain ratio,and develop a compound starter for traditional cheese production;take the yield and texture characteristics as the index,and use the single starter addition amount,whey discharge temperature,and heating and stirring temperature as indicators.Factors and orthogonal experiments to optimize the best process conditions for traditional cheese production,and to discuss the quality changes of traditional cheese during storage.The results of the study are as follows:(1)67 strains of lactic acid bacteria were isolated and purified from traditional cheese,and 10 strains of lactic acid bacteria with good curd state,uniform and delicate tissue and strong aroma-producing ability were screened out with acid-producing,aroma-producing performance and tissue state as indexes.(2)The fermentation characteristics of 10 lactic acid bacteria in milk were re-screened,and three high-quality lactic acid bacteria were obtained,which were NDF 9-3,NDF 10-4 and CH 3-1.According to 16 S r RNA molecular identification,NDF 9-3,NDF 10-4 and CH 3-1 were identified as Pediococcus pentosaceus,Lactobacillus delbrueckii subsp.bulgaricus and Lactobacillus lactis respectively.The growth characteristics of three high-quality lactic acid bacteria were analyzed.(3)Taking curd time,acidity,tissue state and texture characteristics as indexes,three strains of high-quality lactic acid bacteria were fermented with different combinations and ratios,and the optimum ratio of compound auxiliary starter for cheese production in the experimental group was determined as NDF 9-3: NDF 10-4:CH 3-1 = 5: 4: 1.(4)Through single factor and orthogonal experiments on the cheese production process,the best process parameters are determined: the additive amount of the compound starter is 3%,the whey discharge temperature is 60?,and the heating and stirring temperature is 85?.At this time,the traditional cheese sensory score is86.1±1.4 points,and the yield rate is 9.1±0.5%,which is 2.0% higher than the traditional cheese sensory score(84.4±2.1 points),and the yield rate(8.31±0.7%)increased by 9.5 %.(5)After the process optimization,the protein content and ash content of cheese increased,which were 2.86 and 0.15 percentage points higher than those of the control group,respectively.The total amino acid content of the test group was 30.61g/100 g,the saturated fatty acid content was 72.84%,and the foreign starter The addition of the cheese increased the response value of aromatic components and the sensory score was higher than that of the control group.(6)During the storage at 4?,the fat content of cheese with optimized technology decreased,while the protein and ash increased gradually.With the prolongation of storage time,the hardness of cheese in experimental group gradually increased from 3396.31±50.55 g to 5213.06±80.22 g;The color of cheese in the experimental group changed greatly,and the total color difference ? e increased from1.724 at 7 days to 5.504;After storage for 28 days,Mold and Coliforms appeared in the cheese of the experimental group. |
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