Isolation And Control Of Specific Spoilage Organism From Ready-to-eat Penaeus Vannamei During Storage At Room Temperature

Penaeus vannamei has a high yield and is widely loved by the public because of its rich nutritional value and delicious taste.Cooked ready-to-eat food is one of the important product forms of Penaeus vannamei,but it is prone to bag expansion caused by spoilage microorganisms during transportation and storage.In order to extend its shelf life,it is necessary to isolate,study and control specific spoilage organism.Particularly important.This article takes the instant Penaeus vannamei as the research object,isolates specific spoilage organism,explains its spoilage mechanism,and studies the inhibitory effect and quality effects of essential oils on specific spoilage organism of ready-to-eat Penaeus vannamei.The main research contents are as follows:1.Three dominant bacteria were isolated and purified from spoiled ready-to-eat Penaeus vannamei.The specific spoilage organism were identified as BWX40602 by TVB-N and the total number of colonies.16S rDNA sequencing technology and physiological and biochemical experiments were used to identify the specific spoilage organism as Staphylococcus epidermidis,combined Gram staining and growth properties analysis showed that it is a gram-positive bacteria.The most suitable growth environment is NaCl 4%,pH 7.4,and temperature 37?,which are consistent with the characteristics of Staphylococcus epidermidis.2.Through non-targeted metabonomics to study the corruption mechanism of specific spoilage organism S.epidermidis BWX40602,the metabolite composition and abundance of the control group soaked in normal saline and the treatment group soaked in S.epidermidis BWX40602 were analyzed.Using t test(P value <0.05)combined with orthogonal partial least squares discriminant analysis model(OPLS-DA)(VIP> 1)as the standard for screening differential metabolites,a total of 131 significantly different metabolites were identified and their expression was upregulated.There are 53 out of question and 78 out of down-regulation.There are many harmful metabolites in different metabolites with large difference.The KEGG pathway annotation and enrichment analysis have been carried out on them.It shows that the most significant degree of enrichment is carbon metabolism,methane metabolism and phosphotransferase system.The above content further analyzed the spoilage mechanism of S.epidermidis BWX40602 as a spoilage bacteria.3.The antibacterial activity and antibacterial mechanism of five essential oils on the specific spoilage organism S.epidermidis BWX40602 in the ready-to-eat Penaeus vannamei were studied.The results show that cinnamon essential oil has the best antibacterial effect,showing the largest bacteriostatic zone diameter and the lowest MIC value of 0.25 mg/mL,followed by clove essential oil with a MIC value of 2 mg/mL,and the other three(ginger and star anise Fennel and celery seed)essential oils have poor antibacterial effects,and both have MICs of 8 mg/mL.The antibacterial mechanism was studied through GC-MS analysis of essential oils,biological scanning electron microscopy observations and the effect of cinnamon essential oil on cell permeability.The results showed that cinnamon essential oil destroyed the cell membrane and released intracellular substances to cause cell death.4.To study the effect of cinnamon essential oil on the quality of ready-to-eat Penaeus vannamei,2 mg/mL and 20 mg/mL of cinnamon essential oil were selected for the antibacterial experiment of ready-to-eat Penaeus vannamei.Soaking in sterile distilled water was used as a blank control,and soaking in ethanol was used as a positive control.Sensory evaluation,chromatic aberration,texture,pH,TVB-N,total number of colonies,TBA and biogenic amine were used as evaluation indicators to study the effect of cinnamon essential oil on the quality of ready-to-eat Penaeus vannamei.The results show that the shrimp treated with cinnamon essential oil has obvious antibacterial effect,can delay the spoilage of shrimp,and the effect is the same as that achieved by ethanol treatment.The 20 mg/mL cinnamon essential oil does not significantly improve the effect of delaying the spoilage of the shrimp,and the 20 mg/mL cinnamon essential oil will affect the color and flavor of the shrimp due to its own color and smell.In conclusion,this study isolated specific spoilage bacteria S.epidermidis BWX40602 from spoiled ready-to-eat Penaeus vannamei,and studied the spoilage mechanism of specific spoilage bacteria through metabolomics.Cinnamon essential oil,clove bud essential oil,ginger essential oil,star anise essential oil and celery seed essential oil have an inhibitory effect on S.epidermidis BWX40602,and cinnamon essential oil has the most significant antibacterial effect,which mainly exerts antibacterial effect by destroying cell membranes.The use of 2 mg/mL cinnamon essential oil can significantly extend the shelf life of instant Penaeus vannamei.