Analysis Of Microbial Community Structure In Steamed Bread And The Research On The Pulsed Light Sterilization

All objects of this experiment with steamed bread include epidermis,middle and the center.Through comparing the different of the season,storage time of the sample,various quality indicators of steamed bread were tested,including color,starch properties,water content and organizational structure.Total DNA extraction of steamed bread in the microbial flora,using 16 S universal primers and 18 S interval extension,the library is tested by high-throughput sequencing analysis,obtaining the steamed bread of microorganisms in all species.Through cluster analysis and PCA analysis,the change trend of microbial species of steamed bread mould was obtained,and the application effect of non-thermal sterilization technology was studied.The surface sterilization technology of solid foods represented by steamed bread was established.The main results are as follows:1.During the process of preservation,the pH of the steamed bread was kept at around 6.0,and trend to increase firstly and then decrease.The appearance of mold spots on the third day.In the process of cooking,steamed bread surface and center temperature change results show that the temperature on the surface of steamed bread at 100 has℃ a delay of 12 minutes.The central temperature of the whole cooking process is not long enough,which is the root cause of the difference between the two bacteria.For the difference between the two microorganisms,the method of sterilization is also different.2.Bacteria is obtained by microbial diversity analysis,a total of 7 kingdom,37 genus,48 species,the main species are: Bacillus and Staphylococcus,Fictibacillus,Cyanobacteria,Acinetobacter and Acinetobacter.Bacillus occupy the largest share in all groups,is the absolute superiority strains.Saccharomycetales is the biggest occupancy of 18 S group,more than 50%.The proportion of two kinds of dominant bacteria because they are the main fermentation bacteria in the steamed bread fermentation process,providing unique aroma and flavor for steamed bread.18 kingdom,61 genera,75 species,the main types include: Saccharomycetales Saccharomycetales,Pleosporales,Capnodiales,Dothideomycetes,Rhizopus Rhizopus oryzae.Two kinds of fungi are the main reason for the color change of steamed bread.Among them,there were obvious differences between the center of steamed bread and the structure of the colony,among which the species with significant abundance difference were coelomycetes and yeasts.3.On the basis of the analysis of the microbial community,It is explored by the pulse light of steamed bread on the surface of the microbial killing effect represented by Staphylococcus aureus.Selecting single pulse energy,the number of flash and the distance as a condition of control,and the results show that the pulse light in a single pulse energy of 500 J,9 cm according to distance,the flash according to 16 number fell by 1.7 log CFU/g.In the process of preservation,compared with the control group,it showed a significant lag in five days,indicating that the pulsed light could have a good inhibitory effect on the microorganisms on the surface of steamed bread.4,by pH 4.5, pH 9.5 45℃ ,4 of processing,under the condition of 4 h and 24℃ h Staphylococcus aureus increased susceptibility after treatment of pulse light.All the processed Staphylococcus aureus trend to develop significantly protective effect.The Lux S gene is related to the bactericidal action of Staphylococcus aureus in the resistance to alkaline treatment.