Studies On Influencing Factors And Characters Of Heat-induced Myofibrillar Proteins And Pork Gel

Heat-induced gel of muscle proteins is crucial to many meat products.Pork longissimus dorsi was sampled to study the effects of ionic strength and pH on characteristics of heat-induced gel of myofribrillar proteins(MFP).Effects of compression level on results of TPA were studied by analyzing single factor phosphates experiments.Effects of phosphates(sodium hexametaphophate[HMP],sodium tripolyphopate[STPP],tetrasodium pyrophosphate[TSPP]),nonmeat proteins(soy protein isolate[SPI], wheat protein[WP],peanut protein[PP],sodium caseinate[SCA]),starches(corn starch[CS],modified corn starch[MCS],gel-type modified cassava starch[GMCS]) and hydrocolloids(xanthan[XT], carrageenan[CGN],guar gum[GG]) on texture characteristics of heat-induced gel of myofirbrillar proteins and pork sausage were also studied.The two gel systems were compared with each other.Ratio of phosphates in compound phosphates was optimized using response surface design for different purposes.The main results were stated as follows:1.Ionic strength and pH affected hardness,springiness,resilience,cohesiveness,gumminess and WHC of heat-induced MFP gel(P＜0.01),except that pH had no significant effect on the cohesiveness. Interaction between ionic strength and pH had significant effect on hardness of the hardness(P＜0.05), while it strongly influenced other indicators((P＜0.01)).The situation under which a good gel was apt to form for ionic strength was 0.5 and pH between 6.5 and 7.0.Mechanisms of heat-induced MFP gel in different enviorenment may be different.2.Results of TPA test could better reflect the different effects among factors and treatments when the compression level was 50%,compared with 45%and 55%.3.STPP enhanced characteristics of heat-induced MFP gel,which mainly derived from its effect on pH.since hardness of gel and pH values had strong linear relationship when TSPP was added(R~2=1.000). TSPP regulated pH more effectively than STPP,however,the hardness was lower when TSPP was added(0.5%w/w),while the pH value was 7.64 and 6.82,respectively.Springiness,resilience and cohesiveness of heat-induced MFP gel increased to much extent when using STPP(0.5%w/w).4.Hardness of heat-induced MFP gel was improved by STPP and TSPP with different adding proportions(P＜0.01).The WHC was very significant for STPP(P＜0.01) and the resilience and gumminess were significant(P＜0.05),while the springiness and cohesiveness not significant.STPP affected springiness,resilience,gumminess and WHC of heat-induced MFP gel(P＜0.05).Both of STPP and TSPP had no significant effect on conceives of heat-induced MFP gel,but they showed very significant effect on texture indicators of pork sausage(P＜0.01).The hardness,resilience,cohesiveness and guminess of heat-induced MFP got higher as the proportion of TSPP and STPP increased.5.Given the range of phosphates as 0.1%to 0.3%,the optimum proportion of mixed phosphates (HMP∶STPP∶TSPP) for minimum cooking loss was 20∶28∶13,for maximum yield of sausage being 10∶30∶19 and for the best sensory evaluation of sausage,1∶1 of STPP and TSPP was resulted.Both the yield and sensory evaluation of sausage would be maximum when the proportion was 10∶30∶11,and minimum cooking loss and maximum yield and sensory evaluation of sausage would be gained when the optimum proportion was 10∶30∶17.5.6.Nonmeat proteins affected springiness heat-induced MFP gel,while they affected shear stress, resilience and cohesiveness of pork sausage.Nonmeat proteins could improve springiness of heat-induced MFP gel(P＜0.05),but there was no significant difference among adding proportions.WHC of heat-induced MFP was higher when using SCA(P＜0.01).All four nonmeat proteins strongly affected shear stress of pork sausage(P＜0.01),and the comprehensive effect of SPI was better than PP,WP and SCA for pork sausage.7.Starches influenced hardness,resilience,gumminess and WHC of heat-induced MFP gel.For pork sausage they affected hardness,resilience and gumminess.CS and MCS(2%,4%) increased hardness of heat-induced MFP gel,while GMCS made it lower(P＜0.01).Pork sausage got higher hardness by addition of MCS and GMCS(P＜0.05).All three starches significantly improved WHC of heat-induced MFP gel(P＜0.01).8.Springiness,resilience and WHC of heat-induced MFP were influenced by hydrocolloids.GG and XT affect texture profile of pork sausage,while CGN had influence on shear stress and springiness of that. GG and XT improved WHC of heat-induced MFP gel.All three hydrocolloids made springiness of heat-induced MFP higher(P＜0.01),but they lowered resilience of the gel.GG,CGN and XT affected shear stress of pork sausage strongly(P＜0.01);XT had great influence on all texture characteristics of pork sausage(P＜0.01).