Analysis Of Predominant Organisms And Shelf Life Predictiive Model Of Frozen Peeled Shrimp

Penaeus vannamei plays an important role in human diets and is considered notonly a reliable source of protein, but also of nutritional significant due to its nutritionand texture. However, the frozen peeled shrimp are perishable products and the shelflife is limited in the presence of air and atmospheric oxygen, which also lead to thegrowth of aerobic spoilage microorganisms. Because of the complicated constituentsof shrimp, multidimensional data cannot be directly observed and is difficult tointerpret as it is. However, tests take time to complete, microbiologists can onlyconfirm that a product was safe a few hours, or more often, a few days ago. For theseafood industry, predicting the future is not an optional feature. It is an essential fordoing business. It is need that predictive modelling of seafood shelf life and safety isdesigned to address.（1）The purpose of present study was investigat the the frozen peeled shrimp’sprocess for the ensuring of the key quality control points of the frozen peeled shrimpproducts in the period of prosessing.In this paper,these dominant strains of the frozenpeeled shrimp in processing and storage process was isolation and identificationthrough PCR technology and with the help of traditional isolation technolog. Theassumption is that under a given set of circumstances one microorganism will be thedominant spoiler, so modelling this organism can allow spoilage to be predicted. Forcritical processes, the model of during the processing and storage process of thefrozen peeled shrimp products must be validated with challenge tests using the actualproducts and processing conditions to which it is to be applied. The same applies tovirtually all models available for predicting the safety and shelf life of seafood.Although they give predictions, the accuracyof those predictions must be tested.. Thedominant strains of the frozen peeled shrimp in processing were Pseudoalteromonassp, Aeromonas sp and Kurthia gibsonii strain sp.（2）Through analysis the frozen peeled shrimp initial bacteria and the shelf life of thebacteria bacterial phase,througth PCR teehnology and with the help of traditionalisolation technolog. The bacteria flora changes in cold storage and dominate spoilagebacteria of t the frozen peeled shrimp products were discussed．The microflora of first level dominant organisms were Pseudoalteromonas sp, Aeromonas sp and Kurthiagibsonii strain sp.The dominant organisms were composed of Pseudoalteromonassp, Aeromonas sp, Shewanella sp, Chryseobacterium sp at the end of shelf life.dominate spoilage bacteria that isolated from the frozen peeled shrimp products wereinoculated to the no contamination longissimus musele inorder to study the microbialeffect on the frozen peeled shrimp products spoilage quality. The yield factor forproduction of metabolite and the cell concentration determined at the time ofoff-odour detection were used as quantitative measurements of microbial spoilageability．The specific spoilage organisms were composed of Pseudoalteromonassp,Aeromonas sp,Shewanella sp,Chryseobacterium sp. With the apparent andcharacter,the results from microbiological behaviors analysis,Standard guidelines foracceptable levels of the frozen peeled shrimp products use total viable counts （TVC）or aerobic plate counts （APC） with levels of more than the average number ofspecifics spoilage microorg anisms107.07cfu/g being considered unacceptable.（3）The SSO from the frozen peeled shrimp products were inoculated to the no-contamination longissimus musele,then the samples were tray-packaged at0℃,5℃,10℃,15℃,20℃and25℃.The results from microbiological behaviors analysisshowed that model based on Gompertz type model inactivation may be accurate ofdescribed the specifics spoilage micoorrganisms dynamics under0-25℃.Thecorrelation regrcssion showed that Belehradek model could well describe theinfluence of temperature on kinetic parameters μmax（maximum specific growth rate）and λ （1ag phase）with R of0.948and0.933respectively. Consequently, the numberof SSO and the concentration of their metabolites can be used as objective qualityindices for shelf life determination in seafoods.Adopt Gompertz regression equationto describe the growth curve of SSO stored aerobically at0℃,5℃,10℃,15℃,20℃and25℃. We gained growth kinetics model parameters of SSO.According to the growthchanges of SSO in cold storage we build the remaining shelf life （SL） modle asfollows：SL=λ-[（9.13-N₀）/（μmax×2.718）]×{ln[-ln（7.07-N₀）/（9.13-N₀）]-1}For critical processes, the model must be validated with challenge tests using theactual products and processing conditions to which it is to be applied. The sameapplies to virtually all models available for predicting the safety and shelf life ofseafood. Although they give predictions,the accuracy of those predictions must betested. The above model was tested by observed SL at temperatures10℃,15℃and 20℃.Relative error between predicted SL and real SL were8.5%,8.2%and1.5%at10℃,15℃a nd20℃.Respectively,indicating the developed models were valuable forrapid and realistic prediction of the freshness quality and remaining SL of frozenpeeled shrimp products cultured stored aerobicallyat0-25℃.Bias and accuraey afctorswere used as comparison indiecs and range from0.89to1.12and from1.08to1.23，respectively.