Studies On Processing Technology And Storage Stability Of Intermediate Moisture Grass Carp(Ctenopharyngodon Idellus)

Grass carp （Ctenopharyngodon idellus） is one of the importantfreshwater fishes in China, and it is very popular, due to it is delicious andnutritional. But it is not be fully utilized, because of it is seasonal, and it iseasy to corruption. Intermediate moisture food technology is a new kind offood processing and preservation method. Usually the water activity is0.65to0.90（moisture content is15to40%）, and it is soft, nutrition loss less,colour and taste is closer to the fresh fish. In this thesis, the processingtechnology and storage stability of intermediate moisture grass carp werestudied, and the results were showed as follows.Comparing different salting methods of dry salting, wet salting, wetsalting with vinegar and vacuum pluse tumbling salting influence to thesalting characteristics of dried grass carp, the result showed that to achievethe same salinity, vacuum pluse tumbling, dry salting required less timethan wet salting and wet salting with vinegar. The influence of these saltingmethods to the phy-chemical and microbiological index of grass carp was studied, when the salt content was same with each other. wet salting and thewet salting with vinegar samples’TBA content, total volatile basic （TVB-N）content, pH value, amino nitrogen （AAN） were the minimum, followed byvacuum pluse tumbling, and drying salting’s above indexes content was thehighest. Different salting methods’ influence to grass carp protein wasdifferent, wet salting’s influence to the salt soluble protein and proteinextraction rate, WHC （water holding capacity） was minimum, followed byvacuum pluse tumbling and dry salting, wet salting with vinegar was mostnotable. wet salting can maintain the activity of ATPase enzyme and MFI（muscle fiber the fragile degree）, vacuum pluse tumbling and dry salting’sinfluence were at the same level, the biggest was wet salting with vinegar,Overall different salting methods had significant influence to salting rateand chemical index. Comprehensive consideration, wet salting can bettermaintain fish’s freshness, therefore, wet salting can be chosed as the mosteffective way for salting.The influence of different salt concentrations of5%²5%（w/w） onthe salting kinetic of grass carp was studied. The process yield of the grasscarp increased with the decreasing salt concentration, when saltconcentration was below10%, the grass carp’s yield was above1and whenthe salt concentration was above15%, the yield was below1. The saltingkinetic parameter value of k₂for total and water weight changes （ΔM_t^w）and（ΔM_t^w） decreased with increasing salt concentration. Inversely, higher salting kinetic parameter value of k2for salt weight changes （ΔM_t^w） wereobserved for higher brine concentrations. A Linear relationship between theNaCl concentration on a dry basis (X^{NaCl（d.b）}) and t^0.5（t-brining time） wasestablished. Furthermore, the highest effective diffusion values were foundin the grass carp brined at5%and20%.The influence of salting process to drying characteristics of grass carpwas studied. It showed that with increased of salt concentration, saltingtime and salting rate, the weight change rate, and the change values ofmoisture content and water activity of dried fish decreased significantly.L*increased at first and then decreased with the salting degree increasing,while b*increased with the increasing of salting degree. Besides the effectof tertiary butyl hydroquinone （TBHQ）, butylated hydroxyanisole （BHA）,D-ascorbic acid sodium （D-Vc） with the same level to inhibit the oxidationof fish was studied when they were dried. It showed the TBHQ displayedthe best effect of inhiting the oxidation.The effect of different treatments to maintain the quality of fish at37℃of T₁of1.5%chitosan+0.1%potassium sorbate+0.15%TBHQ+vacuum packaging, T₂of2%chitosan+0.1%potassium sorbate+0.15%TBHQ+vacuum packaging, and T₃of2%chitosan+0.1%potassiumsorbate+0.15%TBHQ+modified atmosphere packaging was studied.TVB-N, TBA, AAN, pH value increased with the extension of storage time,2%chitosan film worked significantly better than1.5%. Different packaging methods had significant effects to fish’s quality in storage period,vacuum packaged sample had a better quality than modified atmospherepackaging （CO₂/N₂/O₂=40%/30%/30%）.