Study On Preservation Effect Of Compound Natural Preservatives And Shelf-life Prediction Model Establishment For Drunk Bullacta Exarata

In this paper,drunk bullacta exarata was looked as experimental material.Firstly,main types of spoilage bacteria in it were isolated and identified primarily.Secondly,primary spoilage bacteria isolated from drunk bullacta exarata as an object,carrry on screening,compound and optimized of natural preservative by antibacterial experiments to obtain a new type of compound natural preservative.And then,the effect of this compound natural preservative on drunk bullacta exarata was studied.Finally,the shelf-life prediction model of drunk bullacta exarata was established based on the theory of predictive microbiology.The main results are as follows:1.Main types of spoilage bacteria in drunk bullacta exarata were isolated and identified.For identification,traditional culture technique and 16S rDNA gene of the isolated pure strains were sequenced and analyzed.The results indicated that the primary spoilage bacteria from drunk bullacta exarata stored under 4? at the end of the shelf-life were M1 Moraxella osloensis,M2 Enhydrobacter aerosaccus and L Leuconostoc mesenteroides.2.Compound natural preservative was developed.The primary spoilage bacteria isolated from drunk bullacta exarata were as indicative bacterias,carrry on screening,compound of natural preservative by antibacterial experiments to obtain several natural preservative which inhibitory effect is significant,and then compound and optimized by orthogonal test.The results showed that the optimum proportion of the combination of 0.30 mg/mL nisin+0.30 mg/mL lysozyme+4%garlic juice+7 mg/mL rosemary extract.Finally,the bacteriostatic activity of this compound natural preservative are studied,the results found that the abiotic factors such as temperature,ionic strength,pH and sucrose concentration can not affect the bacteriostatic activity of compound natural preservative,but metal ions such as Mn2+?Cu2+?Fe3+?Zn2+can strengthen its antibacterial activity significantly(p<0.05),and Ca2+?Mg2+?K+influence on its antimicrobial activity was not significant(p>0.05).3.The preservation effect of compound natural preservative in drunk bullacta exarata was studied.The compound natural preservative was applied to drunk bullacta exarata,and total microbial counts,TVB-N value,sense organ evaluation,texture,biogenic amine and so on were taked as the index to appraise its preservation effect.The results showed that the compound natural preservative could prolong the shelf-life of drunk bullacta exarata stored at 4? from 80 days to 110 days.4.The shelf-life prediction model of drunk bullacta exarata was established.The total microbial count in drunk bullacta exarata at different temperature(4?,7?,10?,15?,20? and 25?)were measured and the modified Gompertz model was applied to fit the growth curve of total microbial count,The maximum specific growth rate ?max and lag phase? were calculated and growth kinetic models(primary model)were obtained.Then the influence of temperature on the growth kinetics were studied by Belehradek equation,founding that growth temperature of total microbial count had a good linear relationship with?max and ?.So the secondary model was established,and it has better fitting degree was verified.The limitation of total microbial count organisms were determined according to the linear relationship between total microbial counts and TVB-N value.Finally,the shelf life prediction model was established as SL=?-[(9.533-N0)/(?max×2.718)]×{ln[-ln(4.5814N0)/(9.533-N0))]-1} and it was relatively reliable by compare with actual test results.