| Chilled tan mutton has low fat content,good taste and rich nutritional value.Nevertheless,due to oxidation reaction and microbial contamination,the deterioration of chilled tan mutton during transportation and storage,which seriously hindered the development of tan mutton industry in Ningxia.Therefore,this study focused on the problems of chilled tan mutton,such as easy deterioration,short shelf life and low commodity value during storage.Through single factor experiment and response surface experiment,the optimal formula of compound natural preservative with cinnamon essential oil,lysozyme and nisin was explored.The preservative effect of compound natural preservative on chilled tan mutton during storage was characterized by sensory scores,water holding capacity(purge loss,cooking loss and centrifugal loss),textural properties(hardness,springiness and gumminess),color(L*value,a*value and b*value),pH value,thiobarbituric acid reactive substance value(TABRS),total volatile basic nitrogen value(TVB-N)and total viable count(TVC);Based on 16S rRNA high-throughput sequencing technology,the effects of compound natural preservative on the changes and diversity of microflora of chilled tan mutton during storage were explored,and the bacteriostatic preservation effect of compound natural preservative was evaluated.This study provided theoretical basis and technical reference for the application and promotion of compound natural preservative.The main findings are as follows.(1)Optimization and validation of optimum formula of compound natural preservativeThe results of single factor experiments showed that optimal preservation concentration of cinnamon essential oil ranged from 0.18%to 0.30%;optimal preservation concentration of lysozyme ranged from 0.15%to 0.25%;optimal preservation of Nisin concentration ranged from 0.08%to 0.12%.Response surface experiment was designed with different concentrations of cinnamon essential oil,lysozyme and Nisin as factors to obtain the optimal formula of compound natural preservative is 0.22%cinnamon essential oil,0.27%lysozyme and 0.11%Nisin.Under this condition,the TVC and TBARS of vacuum packed chilled tan mutton on day 7 of storage were 3.23±0.15 lg(CFU/g)and 0.33±0.04 mg/kg,respectively.This proved that compound natural preservative has better preservation effect.(2)Preservation effect of compound natural preservative on chilled Tan muttonThe experimental results showed that with the extension of storage time,the viscosity,b*value,pH value,TBARS value,TVB-B value and TVC increased in control group and treatment group,while the sensory scores,water holding capacity,textural properties,L*value and a*value decreased.Compared with the control group,the natural preservatives in the treatment group more effectively inhibited the growth of microorganisms and the occurrence of oxidation reaction,delayed the decline of sensory scores,reduced the loss of juice,maintained good texture characteristics and color,effectively improved the quality of meat,and extended the shelf life of about 8 days through synergistic effects.In addition,correlation analysis showed that there was significant correlation among the quality indexes of chilled tan mutton during storage(P<0.05),and all of them could reflect its quality.(3)Effect of compound natural preservative on microflora succession of chilled tan muttonThe results of high-throughput sequencing showed that 4 434 606 valid sequences with an average length of 411 bp were obtained from chilled tan mutton during the storage period,and the experimental results could cover most of the microbial information with high reliability.Alpha diversity analysis showed that the microbial abundance,diversity and distribution of samples in the two groups were higher in the early storage period than in the middle and late storage periods,and the microbial abundance,diversity and distribution of samples in the treatment group were always higher than those in the control group at different time points of storage,indicating that the compound natural preservative inhibited the proliferation of dominant spoilage bacteria in mutton.At the phylum level,the dominant phyla in the initial sample and the control group during storage period were both Proteobacteria and Firmicutes,with an average abundance ratio of 70.16%and 26.21%,respectively.Moreover,the abundance ratio of Firmicutes in the treatment group decreased to about 10%during the middle and late storage periods after being treated with compound natural preservative.At the genus level,Acinetobacter was the dominant genus with relatively high abundance in the initial sample.During storage,Serratia,Carnobacterium and Pseudomonas were the dominant genera in the control groups,with the average relative abundance ratio of 26.78%,13.02%and 10.26%,respectively.The abundance ratio of Serratia and Carnobacterium was decreased by the treatment of natural preservative. |
