Microbial Diversity And Shelf-life Predictive Model Of Bulk Sauced Duck Products

Bulk sauced duck is easily contaminated by microoganisms with rich nourishment, high water activity and low-temperrature sterilization process.This may not only lead to economic losses, also may threaten the healty of comsumers, limiting greatly the shelves and sales radius. It is difficult to quickly and accurately determine the shelf-life by sensory evaluation, while traditional microbiologial analysis always in hindsight. Therefore,it is necessary to develop a rapid and effective method for determining the shelf-life, ensuring the edible security of bulk sauced duck and promoting the healthy and orderly development of the industry.From the perspective of microbial ecological, this paper analysed microbial populations diversity and main flora on bulk sauced duck during storage and determined specific spoilage organisms（SSO）. On this basis, in order to achieve the result of “prophet” without traditional microbiological testing and help related enterprises solve the problem of product shelf life and safety, shelf-life prediction model for bulk sauced duck was developed by predictive microbiology.The contents and results are as follows: 1 Microbial populations diversity of bulk sauced duck during storage by MiSeq SequencingLittle is known about the role of SSO and what other micro-organisms are present and these organisms may indirectly influence spoilage by their interactions with SSO in sauced duck with bulk packaging. We have carried out culture independent Illumina MiSeq sequencing analysis of the V3-V4 region of 16 S r DNA and internal transcribed spacer（ITS） 1 to gain a more comprehensive insight about changes in microbial populations diversity and main flora on sauced duck during storage at 4℃ and 25℃, providing a theoretical foundation for determining SSO. Results indicated that bacterial and fungal species diversity showed a downward trend in general during 4 and 25 storage℃ ℃. The initial bacteria were dominated by the species Weissella sp., Staphylococcus sp. and unclassified Enterobacteriaceae, and the advantage fungi corresponded to Debaryomyces sp. IZ₁257 and Lodderomyces elongisporus. During the middle and later periods of the 4℃ storage Psychrobacter pulmonis and Staphylococcus sp. were the main bacterial. While the predominant bacteria flora was Weissella sp., Staphylococcus sp., Macrococcus caseolyticus and unclassified Enterobacteriaceae stored at 25℃. Debaryomyces sp. IZ₁257 was the dominant fungi during 4 and 25 storage℃ ℃. Advancements in Illumina MiSeq sequencing having the full potential for obtaining a complete coverage of microbial communities in a given community are revolutionizing our assessment and comprehension of microbial communities, when compared with culture-dependant methods. 2 Determination SSO of bulk sauced duck productsTo determination the SSO of bulk sauced duck products, the physicochemical and sensory evaluation were analyzed during storage at 4℃ and 25℃, and the correlation of these values with the amounts of microbial were also analyzed. Results showed that SSO was different under different storage conditions. LAB, Enterobacteriaceae and Staphylococcus should be the SSO of bulk sauced duck during storage at and 25℃, and Ns was determined as 7.09 lg（cfu/g）. Psychrophiles should be the SSO of bulk sauced duck during storage at 4℃, and Ns was determined as 6.71 lg（cfu/g）. 3 Microbial growth kinetics models for SSO and shelf-life prediction model for bulk sauced duckBulk sauced duck were selected as subjects in this study. The amounts of LAB were calculated directly from samples during storage at 10℃,15℃,20℃ and 25℃.Modified Gompertz model were used as primary model to fit observed data, and shelf-life prediction model was developed. The results showed that the modified Gompertz model could give a good description of LAB under different storage temperature, the values of RAdj2 were 0.9989, 0.9810, 0.9797 and 0.9901 respectively. To test the validity of the models, another experiment was conducted with different batch of bulk sauced duck stored under 25℃. Results verified the models were imperfection, needing to optimize the model in the field of the actual flow. Belehradek model symbolically described the good linear realationship between μmax1/2,（1/λ）1/2 and temperature by residual analysis respectively. The shelf-life prediction model which can predict the shelf-life of bulk sauced duck under 10²5℃ was developed.