The Combined Effect Of CO₂ And Cold Seawater On Preservation Of Pacific White Shrimp

Pacific white shrimp(Litopenaeus vannamei)was native to the coastals of South Pacific and one of three highest global aquaculture shrimp production.The low commodity values of shrimp was mainly associated with the seasonal harvesting,spoilage after capturing and melanosis.C02 cold sea water was a promising preservation technology owing to its low pH,low temperature and a certain amount of salt.The treatment of shrimp by CO2 cold sea water may inhibit the growth of microorganisms and restrained the enzymatic reaction process by polyphenol oxidase.The effect of CO2 cold sea water on preservation of shrimp was systematiclly studied.Different anti-browning agents and modified atmosphere packaging technology are also used in this thesis.1.The effect of C02 cold seawater on preservation of Pacific white shrimp were investigated.The results showed that Pacific white shrimp treated with C02 cold seawater had a better role in preservation than the group with the cold seawater and control.C02 cold sea water could be more effective to inhibit the total viable counts.It could also significantly reduce TVB-N and K values,delay shrimp browning and protein denaturation during storage.As a result,the effect of C02 cold seawater could prolong the shelf-life for 4 days.2.The shrimp pretreatment with C02 cold seawater on the quality of Pacific white shrimp was studied.The shrimp was immersed in CO2 cold seawater for Oh(control),0.5h,6h,24h.All samples were storaged in refrigerator at 4? for 8 days.The shrimps treated with C02cold seawater for 24h significantly(p<0.05)slowed down total viable counts,and biochemical indexes(pH,total volatile base,amino nitrogen,myofibril extractability)also had a slower development.The results was shown that the immersion for 24h could be a suitable pretreatment time.3.The addition of different natural additives to CO2 cold seawater on the qualities of Pacific white shrimp was studied.The results were shown that C02 cold seawater with 2%4-HR,Phytic acid and gluconic acid-8-lactone could enhance the original preservation effect and extend the shelf life up to 10 days.Among the three groups,phytic acid and Gluconic acid-8-lactone had the better effects in lowing of the total bactial count,TVB-N,K-value and relative activities of polyphenol-oxidase)than that of 4-HR(p<0.05).Ascorbic acid,citric acid and trehalose had different preservation effects.The effect of natural additives on the total bactial count,TVB-N,and relative activities of polyphenol-oxidase of shrimp during the storage,was better than control,but the difference was not significant in different treatment(p>0.05).4.The effect of different proportions of gases in modified atmosphere packaging on the preservation of Pacific white shrimp was studied.The results showed that 40%C02 +60%N2 and 85%C02+5%02+10%N2's total viable counts slowed down significantly(p<0.05)than any other groups(p<0.05)could have the better effect among all the samples.What's more,these two experimental groups also had a slower development of pH,TVB-N and other indexs.According to the results of activity of polyphenol-oxidase index was studied,these two experimental groups had a slower tenderness content.As a result,the experimental group extended the shelf-life to lOds.5.The effect of modified atmosphere packaging technology combined with mixed additives and CO2 cold seawater for preservation of Pacific white shrimp was studied.The results showed that the effect of mixed additives with modified atmosphere packaging(40%CO2+ 60%N2 and 85%CO2+5%O2+10%N2)could control the total viable counts and the content of TVB-N,which could extend its shelf life up to 12d.