Study On Fresh-keeping Technology Of Pelteobagrus Fulvidraco

Pelteobagrus fulvidraco are highly susceptible to spoilage and deterioration during cold storage due to their high moisture content,high protein and neutral flesh quality.The spoilage of freshwater fish is mainly caused by the action of specific spoilage bacteria in the fish flesh.The microorganisms carried on the body surface,gills and flesh of frozen Pelteobagrus fulvidraco grow and multiply after death,leading to spoilage of the fish.In this paper,we used Pelteobagrus fulvidraco as the research object to investigate the quality change pattern of Pelteobagrus fulvidraco during refrigeration,and applied high-throughput sequencing technology to study the microbial community diversity during the decay of Pelteobagrus fulvidraco in the refrigerated temperature zone of 0～4℃,to investigate the dynamic change pattern of its bacterial phase during refrigeration,and to identify the low-temperature specific spoilage bacteria during the refrigerated storage of Pelteobagrus fulvidraco,and also used the traditional selective culture method to the isolated spoilage bacteria during low-temperature storage were isolated and purified separately to obtain the corresponding strains,and the strains were identified.Subsequently,the isolated spoilage bacteria strains were inoculated into sterile Pelteobagrus fulvidraco fish blocks for storage,and the total bacterial count and TVB-N were monitored during storage,and the spoilage-causing ability of the spoilage bacteria was evaluated by the TVB-N yield factor to determine the dominant spoilage-causing bacteria during the cold storage of Pelteobagrus fulvidraco,and based on this,the The biological preservative solution was selected based on the inhibition circle diameter,minimum bactericidal concentration and other indicators,and the orthogonal experiment was designed to optimize the ratio and obtain the best combination of biological preservatives.The main methodology and findings of the thesis are broken down as follows.（1）Dynamic changes of the Micro-biome of Pelteobagrus fulvidraco during refrigerated storage.High-throughput sequencing technology was used to analyze the change patterns of Micro-biome in the decay of Pelteobagrus fulvidraco under storage conditions of 0℃and 4℃.The results showed that the sequenced sequences from the diversity data analysis of 18 samples were quality filtered to obtain 982996 high-quality sequences,and a total of 2070 OTUs were classified on the basis of 97%sequence similarity,with 39 phyla,98 orders,218 orders and 784genera at the taxonomic level.At the phylum level,Pelteobagrus fulvidraco bacteria at 4℃storage temperature were mainly Proteobacteria,Firmicutes,Bacteroidota,Actinobacteriota,while at 0℃storage temperature,a new phylum emerged—Fusobacteriota,The phylum Proteobacteria was the dominant phylum during the whole storage process.At the genus level,549 genera were identified in the 18samples,with Pseudomonas,Aeromonas and Shewanella being the dominant genera during the 0～4℃refrigeration period.（2）Isolation and purification of the dominant spoilage bacteria during storage and analysis of their spoilage-causing ability.A total of 25 strains of bacteria were isolated and purified during the storage of Pelteobagrus fulvidraco at0～4℃,including 14 Gram-negative strains and 11 Gram-positive strains.Macrococcus caseolyticus、Aeromonas hydrophila、Kurthia gibsonii、Chryseobacterium candidae、Shewanella putrefaciens、Micrococcus yunnanensis、Bacillus velezensis、Streptomyces enissocaesilis.The common spoilage bacteria of fish included Aeromonas and Shewanella,and the decaying ability was from Shewanella>Aeromonas in descending order,among which Shewanell was significantly stronger than Aeromonas in terms of decaying ability.The predominant spoilage bacteria of the Pelteobagrus fulvidraco were identified as Aeromonas and Shewanella.（3）Screening of biological preservation solutions and application of composite preservation agents.According to the inhibition mechanism of relevant Gram-negative bacteria,ten bio-preservatives,such as chitosan,tea polyphenol,lysozyme,sodium lactate,sodium dehydroacetate,ε-polylysine,rosemary extract,grape seed extract,phytic acid and potassium cinnamate were selected.Through the determination of inhibition circle diameter,inhibition rate and other indicators,ε-polylysine,tea polyphenol and Lysozyme showed better bacterial inhibition effect.After the orthogonal analysis,the best combination of freshness preservatives were A₂B₃C₃,A₃B₃C₃,and the best combination of freshness preservatives were 0.45g/kg of tea polyphenols,0.5g/kg of lysozyme and 0.25g/kg ofε-polylysine.The shelf life of Pelteobagrus fulvidraco was increased from 6～8d to 10～12d without preservation,and all the physical and chemical indicators did not reach the spoilage standard,and the sensory quality was excellent.