Curing Fish With Multi-strains And The Detecting Of Security Indicators

As a traditional delicious food in our country，cured fish was welcomed bymost consumers due to its unique flavor，close texture and rich nutrition，whichbrought big proportation for cured fish in the market．However，traditional curedfish was mainly produced in the small workshop under high salinity and lowtemperature conditions，products were usually unstable and with high salinity andlow safety， besides， its production was not continuous for the impact ofseasons．The unique flavor of cured fish mainly depended on the microorganisminfected in the curing process and enzyme metabolized by these microorganism，butnot only the species but also the amount of infected microorganism couldn’t becontroled，which may leading to discontinuity in the aspect of qualities especiallywhen cured fish were produced in different batches，and the seculity of productscan’t be guaranteed，besides，higher demand for food security were asked byconsumers，cured fish which were produced under traditional conditions couldn’tmeet the demand of consumers for security，so a better technology for improvingcured fish needed to be explored in order to make the products safer．In this study，curing method was considered mainly from the security aspects and the securityindicators were detected，the conclutions of this study were showed below:（1）Fermentation strains were determined according to the fermentationcharacteristics of dominant bacteria in the traditional cured fish，in this study，thefermentation characteristics included salt tolerance，nitrite tolerance，antibioticactivities， reductivities of hydrogen peroxide and nitrate，lipase activities．Amongthe five dominant bacteria Lactobacillus plantarum(Lp)， Pediococcuspentosaceus(Pp)， Lactobacillus casei(Lc)， Staphylococcus xylosus(Sx) andStaphylococcus carnosus(Sc)，Sx had a stronger salt tolerance，Sx and Sc showedless susception to nitrite，the antibiotic activities of Pp were stronger whencompared with the other four bacteria，the reductivities of hydrogen peroxide and nitrate，lipase activities of both Sx and Sc were positive．Pp and Sx were chosen asthe fermentative strains for curing fish according to comprehensive comparison．（2）Acid value，peroxide value，TBA value，TVB-N，nitrite，nitrate，totalamount of bacteria were used as the inditors for the security of cured fish whencured fish was produced under different conditions，when the ratio of Pp and Sxwas1:1，inoculum amount were106CFU/g，salt amount was5%，curing temperaturewas10℃，products showed higher security．（3）After test group was cured according to the best technology while controlgroup was cured without inoculum，the acid value，peroxide value，TBA value，TVB-N，nitrite，nitrate of the test group were respectively0.108mgKOH/g、0.130g/kg、1.457mg/kg、12.34mg/100g、1.480mg/kg、0.167mg/g，while the controlgroup were0.154mgKOH/g，0.189g/kg，1.636mg/kg，17.86mg/100g，1.693mg/kg，0.188mg/g，the test group reduced by29.87%，31.22%，10.94%，30.91%，12.58%，11.17%when compared with the control group，the total amount of bacteria in thetest group was1.52×106CFU/g while in the control group was3.85×105CFU/g，thedetected E. coli in the inoculum group and non-inoculum group were all under3MPN/100，Salmonella were not detected in both groups，Staphylococcus aureuswas detected in the non-inoculum group but the inoculum group was not，aftercomparation between the test group and the control group，the results showed thatinoculum can improve the safety of the crued fish．（4）The acid value，peroxide value，TBA value，TVB-N，nitrite，nitrate werehigher than that of before drying after cured fish was dried under30°C，40°C，50°C，60°C，70°C hot air drying，but the total amount of bacteria under50-70℃was lower than that of before drying，60℃hot air drying was the more suitable hotair drying temperature for drying cured fish．Vacuum freeze-drying showed to bethe best way for drying when different methods were compared，except the totalamount of bacteria，other indicators detected were only slightly higher than those ofbefore drying．When the higher cost of vacuum freeze-drying was taken into account，at the same time all the indictors detected after60℃hot air drying wereall within the safe range，so60℃hot air drying can be used as the drying methodfor producing cured fish in large scale with the strains Pp and Sx．（5）When cured fish was dried under the best drying conditions，acid value，peroxide value，TBA value，TVB-N，nitrite，nitrate of the inoculated group wererespectively0.210mgKOH/g，0.210g/kg，2.054mg/kg，17.21mg/100g，2.107mg/kg，0.261mg/g， while the control group without inoculum were respectively0.365mgKOH/g，0.407g/kg，2.929mg/kg，29.23mg/100g，2.483mg/kg，0.401mg/g，the test group reduced by42.47%，48.40%，29.87%，41.12%，15.14%，34.91%when compared with the control group，after drying，the detected bacteria in the testgroup and the control group was respectively2.8×104CFU/g，3.8×104CFU/g，thedetected E. coli in both groups were all less than3MPN/100g，Salmonella were notdiscovered，Staphylococcus aureus was not discovered in the test group while in thecontrol group was discovered，after being dried，the test group showed higher safetywhen compared with the control group．...