Study On Myofibrils And Myofibrils Gel Properties Of Jumbo Squid (Dosidicus Gigas)

Peru Squid is the informal name of Dosidicus gigas,also named jumbo flying squid.It belongs to Dosidicus Ommastrephidae.It grew rapidly and had quite big shape.The highest concentration occurs off the Peruvian coast in the southern hemisphere and in the Gulf of California in the northern hemisphere.Over recent years,D.gigas became one of the biggest and most abundant cephalopod fisheries in the Pacific Ocean, mainly in Peru and Mexico.But high moisture and disagreeable taste in the muscle of D.gigas utilization of this cephalopod resource.Surimi and surimi-based product are good choice because the disagreeable taste could be removed during the process.The bases of surimi and surimi-based product are myofibrils dissolved in salt solution.The objects of this research were Peru Squid and normal squid sold in market.Myofibrils of squid were extracted and the gel properties were studied to improve gelation capacity of myofibrils.From the concultion metioned above,Peru squid can be a new material for high quality surimi.The result showed giant Peru squid(Carcass weight＞6kg),medium Peru squid(Carcass weight between 3～6kg)and little squid(normal squid sold in market,carcass weight＜1kg)had significance of difference in water content,ashes content and crude protein content.Ammonia content in giant Peru squid was much higher than the other which made giant Peru squid a strange astringent and acerbic flavour.There were more kalium content and less copper,calcium content in Peru squid than little squid and there were no significant difference in other trace element content among the three size squid.Similar protein constitute were observed in giant and medium Peru squid and different with little squid.Time,incubation temperature and ionic intensity showed significant effect on the activity of Ca²⁺-ATPase in Peru squid myofibrils(p＜0.05).Stability of Ca-ATPase could be improved by certain content of sodium chloride.Additives such as nonmuscle protein,starch and Acacia Gum showed significant influence to squid myofibrils gel strength in which soy protein and Acacia Gum exhibited salient effect.Operational conditions assay achieved optimization of giant squid myofibrils gellation adding nonmuscle protein were 4%w/w soy protein,pH 7,50℃heated for 1hrs and 4%w/w soy protein,pH 8,40℃heated for 1.5hrs for both medium and little squid. Operational conditions assay achieved optimization of squid myofibrils gellation adding Acacia Gum protein were 0.5%w/w concentration,pH 7, 50℃heated for 1hrs.TG concentration,time,incubation temperature and pH showed significant influence to squid myofibrils gel strength.Operational conditions assay achieved optimization of squid myofibrils gellation with TG were 2%w/w TG,pH 7,40℃heated for 2hrs.The microstructure showed that the clusters network of squid myofibrils added with soy protein,Acacia Gum and TG were composed by smaller aggregates than those control.The microstructure showed that both the size of the granules and the cavities among clusters seemed to be larger with the TG concentration decreased.Effect of high pressure on gel properties was studied.The result showed gels induced by 300MPa and 400MPa demonstrated better gel strength than other pressure treated gels.Microstructure of surimi gels induced by different high pressure showed significance of difference and exhibited a compact and homogeneous network at 300MPa and 400MPa.Gel hardness of high pressure-induced gels were less than heat-induced(40℃,2h and 90℃,30 min)gels and springness of high pressure-induced gels were higher than heat-induced(40℃,2h and 90℃, 30 min)gels and so gel formed by this two method showed similar gel strength.SDS-PAGE showed high pressure prompted more Actin and Paramyosin aggregating and cross-linked with Myosin or filled into the net-work formed by Myosin heavy chain than heat treated.Operational conditions for Peru squid surimi processed by high pressure were studied.The result showed:Surimi gel strength made from Peru squid was larger as the pressure increasing.Maximum of gel strength arrived at 500MPa,15min which was 7 times to heat-induced(40℃,2h)gels.Gel strength of surimi by high pressure between 300MPa～600MPa all higher than heat treated gels.Surimi gel strength of surimi gels processed by high pressure(300 MPa～600 MPa,10～20min)followed by heat treated(90℃,30 min)were higher than heat treated gels(40℃,2h and 90℃,30 min).Activity wet of giant squid surimi exhibited no significant difference as the pressure changed.The more potato starch added into surimi the higher gel strength.Gel strength of high pressure-induced gels were obviously higher than heat-induced gels with 4%or 6%w/w potato starch.Gel strength of surimi gels adding soy protein increaced along with the rising of pressure.Gel properties of surimi obtained from adding 6%or 8%w/w soy protein and treated by more than 350 MPa were satisfactory.Whiteness of surimi treated by high pressure followed heat showed no significant difference between gels with 6%and 8%w/w potato starch (P＞0.05)while the whiteness of heat-induced gel dropped as the concentration of potato starch rised.Whiteness of surimi achieved maximum treated at 400MPa.Surimi properties were satisfied in these processing conditions.