Analysis Of Microorganisms In Milk Powder Processing Based On High-throughput Sequencing

Consumers are extremely concerned about the safety and quality of infant formula,which is affected by a variety of processing-related issues,with microbes being the greatest unavoidable risk.Among them,microorganisms that are more challenging to handle by conventional cleaning methods during processing still need to be explored through our current studies,in order to ensure production safety and product quality through a thorough understanding of the relevant physicochemical properties of these microorganisms.The main research contents of this study are as follows: In order to analyze the diversity of microorganisms in the processing of infant formula,the change pattern in the process,and to derive the dominant flora through the process,Illumina Miseq high-throughput sequencing was used.The dominant flora were further isolated by culturable means,the dominant flora were detected,and the actual samples were tested after the construction of the test system.the main research contents are as follows:1.The diversity of microorganisms and their succession patterns during the processing of dairy powder were studied by high-throughput sequencing.The main change patterns were based on the Chao1 index,and Shannon’s results showed that microbial species and diversity gradually decreased with the formation of products,and 21 bacterial phyla and 339 bacterial genera were identified by high-throughput sequencing.Among them,Firmicutes,Proteobacteria,Bacteroidota,and Actinobacteriota were the most abundant in relative terms at the phylum classification level.The Bacillus,Gammaproteobacteria,Alphaproteobacteria,and Bacteroidia were the largest at the phylum classification level,of which Bacillus accounted for56.14%.where the dominant genera were Streptococcus,Lactococcus,and Enterococcus.2.The isolation of culturable microorganisms was used to further understand the distribution of microorganisms during processing.The test results were basically the same as the microbial diversity trend indicated by high-throughput sequencing results,with the highest number of microorganisms isolated from raw milk and the lowest from finished powder.And a total of 208 strains of bacteria were isolated,and 8different bacteria were obtained by sensory evaluation and initial screening of the morphology,size,consistency,and color of the colonies on solid media for convenience.And the molecular biology identification of these eight strains,and finally getting six different types of strains,the test results a re mainly Bacillus class strains.Through the physiological and biochemical tests with bacterial Berger’s manual,Bacillus cereus was identified,but also to verify the reliability of molecular biology means.3.To detect Bacillus cereus,we screened the virulence genes by reading the literature,tested whether Bacillus cereus isolated in this thesis had virulence genes,designed specific primers based on the detection results,performed sensitivity and specificity tests on the specific primers,and constructed a nhe gene in Bacillus cereus.A PCR assay was constructed for the detection of the nhe gene in Bacillus cereus,and the effect of the PCR technique in actual samples was explored,Traceability analysis of the dominant microorganisms was performed in conjunction with the contents of Chapter 2,where Bacillus cereus was mainly in the temporary storage group.