Isolation,Identification And Inhibition Of Specific Spoilage Organism In Catfish Fillet

With more meat,less prickly and rich nutrient,catfish is favorite by the consumer.But the catfish water content is high,it is easy to spoilage.Short shelf-life limits the fresh catfish fillets and its product sales and circulation.Therefore,to find effective preservation methods to improve the economic benefit of industry is important significantly for catfish farming and processing.The specific spoilage bacteria(Special Spoilage Organisms,SSOs)is one of the major factors causing fish corruption.In this experiment,leather Catfish fish were used as experimental material.Vacuum packaging,modified atmosphere packaging ice temperature storage,cold storage tray packaging were used to determine its shelf life,and screened to obtain the advantages of spoilage bacteria,further to determine the ability of corruption catfish fish SSOs.And SSOs was used to find the appropriate natural preservative for catfish fresh.The main contents and results are as follows:1.The catfish fillets vacuum-packed(VP)was stored ice temperature(-0.7±0.01?)conditions.Using metagenomics technology,measurement and analysis of all microbial 16S rDNA sequences of fresh catfish fillets(0 d),VP catfish fillets storage section 10,20 d.The results showed that fresh catfish fillets has higher abundance and diversity of flora,while flora richness and diversity of the VP catfish fillets decreased during storage,and became the dominant part of the microbial flora.During storage of VP catfish fillets in the ice temperature,genus Lactococcus lactis became the main spoilage bacteria.2.In the traditional isolation streaking method,analysis,separation and purification of dominant spoilage bacteria were performed during AP refrigerated,VP ice temperature storage,and the modified atmosphere packaging(60%CO2 40%02,MAP)ice temperature storage catfish fillets and determination of 16S rDNA gene sequences was used to identify microbial species.Results showed the advantage of spoilage bacteria for AP group was Pseudomonas sp.and Shewanella sp.and a total of four representative strains,Pseudomonas cedrina,Pseudomonas fluorescens,Pseudomonas fragi,Shewanella putrefaciens,were identified.For VP group,advantage spoilage bacteria is Lactooccus sp and Aeromonas sp,and identified four representative strains,Lactococcus raffinolactis,Aeromonas salmonicida,Pseudomonas fragi,Pseudomonas.Trivialis,were identified.For MAP group,advantage for the spoilage bacteria was Lactococcus sp and Aeromonas sp,seven representative strains,Lactobacillus sakei,Carnobacterium sp.R-1,Lactococcus raffinolactis,Aeromonas salmonicida,Aeromonas sobria,Pseudomonas lundensis,were identified.3.Different strains were inoculated with sterilization catfish fillets.AP,VP and MAP,and refrigeration and ice temperature storage were performed to measure the senses,the total number of colonies,reducing the value of thiobarbituric acid(Thiobarbituric acid reactive substances,TBARS)and volatile basic nitrogen(Total volatile basic nitrogen,TVB-N)and further to evaluate the ability of different strains of corruption.Results showed for AP group,Pseudomonas fragi corruption was strongest,followed by Pseudomonas fluorescens and Pseudomonas cedrina.For VP group,Lactococcus raffinolactis corruption was strongest,followed by Aeromonas salmonicida and Pseudomonas trivialis.For MAP group,Lactococcus raffinolactis was strongest,followed by Carnobacterium sp.R-1 and Lactobacillus sakei.4.Catfish fillets SSOs in gram positive bacteria-Lactococcus raffinolactis,gram negative bacteria berry Pseudomonas fragi was selected as indicator bacteria.Single factor test was used to screening of natural antimicrobial substances.The results showed that allicin,tea polyphenols and nisin could inhibition of lactic acid bacteria,while tea polyphenols,chitosan and apple polyphenols could inhibit Pseudomonas.Furthermore,response surface method was used for optimization of 2 groups of composite antibacterial agent formula:tea polyphenols 2.86%,1.44%of chitosan,apple polyphenol 0.56%;allicin 0.39%,tea polyphenols 3.26%,Nisin0.05%.5.Three kinds of natural preservation solution(1#preservation solution:polyphenols,chitosan and apple polyphenol;preservation solution 2#:garlic tablets,polyphenols and Nisin;3#preservation solution:chitosan,propolis,Nisin,lysozyme and polyphenols)were compared.The 1#and 3#fresh preservation solution was used for AP catfish fillets 4±1?cold storage,preservation solution 2#and 3#was used for VP and MAP fresh catfish fillets-0.7±0.01? ice temperature storage.The senses,the total number of colonies,change TBARS value,TVB-N and water retention value were analyzed for preservation Preservation Solution on catfish fillets.The results showed that the shelf-life of AP catfish fillets in cold storage was 7 d,shelf life of 1#preservation solution treated catfish fillet was 15 d-20 d,shelf life of 3#preservation solution treated was 10 d,shelf life of VP catfish fillets on ice temperature during storage was 20 d,shelf life of 2#preservation solution treated was 25-30 d,shelf life of 3#preservation solution treated was 35 d,shelf life of MAP catfish fillets in the ice temperature during storage was 30 d,shelf life of 2#preservation solution treated was 35-40 d and shelf life of 3#preservation solution treated was more than 40 d.