| China is the world’s largest producer and consumer of pig,as well as the largest producer of pig related food.Pigskin is a by-product of pork processing,mainly composed of water,protein and a small amount of fat and carbohydrates.It is a favorite food for our Chinese people.Protein accounts for about 35%of the total weight of pigskin,and collagen protein is more than 90%.It is a typical high protein,low fat food,and also has some healthy function.Pigskin is not widely used in food industry except for leather processing,which seriously affects the economic benefits of meat processing enterprises.The special structure of pigskin makes it tough and difficult to break.After heating,The pigskin will become yellow and smell badly.Once it is contaminated by microorganisms,It not only affects the sensory quality,but also directly leads to the shortening of shelf life,which seriously affects the deep processing and utilization of pigskin.In response to the problem of using pigskin in meat companies,this study used high-throughput sequencing technology to study the microbial diversity in pigskin at different temperatures and the diversity of pigskin microbes after heat treatment,providing the use of pigskin in the food industry.After research,this paper draws the following main conclusions:1.High throughput sequencing and bioinformatics analysis of pigskin bacteriaHigh througgput sequencing was performed using Miseq platform,and the community composition of pigskin samples was analyzed at each classification level through quality control screening.Bacteria in pigskin samples at 4,25,37,60,70,80,90,100,110 and 120℃ can be divided into 1 domain,1 boundary,16 phyla,30 classes,71 orders,126 families,273 genera,389 species and 476 OTUs.Pan and Core species analysis curves showed that the total number of OTUs in pigskin samples no longer increased significantly with the increase of sample number,and the total number of OTUs no longer decreased significantly.The results showed that the sample sequencing quantity could reflect the bacterial community structure and diversity of pigskin samples.2.Analysis of Microbial Diversity in Pig skin Cultured at Different TemperaturesThe sequencing quantities of pigskin samples were evaluated by OTU analysis and dilution curve.The results of dilution analysis of pigskin samples at 4,25 and 37℃showed that the sequencing quantities well reflected the structure and diversity of bacterial communities in pigskin samples.Alpha diversity study showed that the total bacterial count and diversity were the most abundant in 25℃pig skin samples,and there was significant difference between 4℃ group and 37℃ group(P<0.05),while the total bacterial count and diversity in 25 and 37℃ pigskin samples were lower,and there was no significant difference between the two groups(P>0.05).Venn chart shows the similarity and overlap of species composition in pigskin samples.The number of specific species in pigskin at 25℃ is much larger than that in pigskin at 4 37℃.It shows that temperature has a great influence on the number of microorganisms in pigskin.Beta diversity was expressed by principal coordinate analysis.There was no obvious overlap between pigskin samples at 4,25 and 37℃indicating that the bacterial community structure in pigskin samples at 4,25 and 37℃was significantly different.The analysis of bacterial community structure showed that the composition of the community in pigskin samples at 4,25and 37℃ was different and varied by comparing the classification of pigskin samples at the gate and genus levels and clustering analysis of Heatmap diagram.The results showed that different storage temperatures have great influence on the bacterial community structure and diversity of pigskin samples.3.Effect of Heat Treatment on Microbial Diversity in Pig skinThe sequencing quantity of the samples was evaluated by dilution curves.The results of dilution analysis of each sample showed that the number of sequencing well reflected the structure and diversity of bacterial communities in pigskin samples.Alpha diversity studies showed that the total number and diversity of bacteria in the 120 and 110 degree ℃ pigskin samples were relatively rich,and the total number and diversity of bacteria in the two groups were similar.The total number and diversity of bacteria in pigskin samples at 60,70,80,90 and 100℃were lower,and the total number and diversity of bacteria in the five groups were similar.The total number of bacteria and the diversity of piglets in 120,110℃ and pigskin samples were higher than those in others.Bacterial composition analysis of pigskin samples showed that with the increase of heat treatment temperature,the number of species observed in pigskin samples showed a "concave",pattern;the number of species observed in pigskin samples at 110 and 120 ℃was significantly higher than other temperatures(p<0.05);while in pigskin samples treated at 60,70,80,90 and 100℃,the richness of samples was similar,and the species observed were similar.The numbers were lower and there was no significant difference(p>0.05).Beta diversity was expressed by principal coordinate analysis,and there was obvious overlap between pigskin samples at 60,70,80 and 90℃,indicating that bacterial community composition was similar and there was no obvious difference in community structure;there was no obvious overlap between pigskin samples at 100,110 and 120℃,but the distance was close,indicating that bacterial species composition in pigskin samples at 100,110 and 120℃ was different,but similar.The analysis of bacterial community structure showed that there were no significant differences in the composition of the community among the five groups of pigskin samples treated at 60,70,80,90 and 100 ℃,and the composition of the community among the pigskin samples treated at 110 and 120℃ was not significant,but there were significant differences between the pigskin samples treated at 60,70,80,90,100℃ and the pigskin samples treated at 110 and 120 ℃.There are great differences in the composition of falls.The results showed that different heat treatment temperatures had great influence on the bacterial community structure and bacterial diversity of pigskin samples. |
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