Study On Texture Changes And Microscopic Mechanical Properties Of Chilled Tan Mutton During Storage

Tan sheep is an advantageous animal species with the characteristics of Ningxia,and has a huge market potential and is now one of the regional pillar industries in Ningxia.The quality control of the postmortem tan mutton is of great practical significance to improve its meat quality and to improve its market value.In this paper,the longissimus dorsi of postmortem tan mutton stored at 4? for 7 days was taken as the research object,and the variation of the internal quality indices(total protein solubility(TPS),myofibril protein solubility(MPS),sarcoplasmic protein solubility(SPS)myofibril fragmentation index(MFI),drip loss rate(DLR),and TPA texture properties(hardness,resilience,springiness,gumminess and chewiness)during postmortem storage period were studied,the change of quality during storage(1?7d)was revealed from the internal and external levels,and combined with its stress relaxation parameters,based on the correlation between the two,the quality prediction models were established to conveniently,accurately and efficiently predicte the postmortem quality of tan mutton.In addition,with the purpose of revealing the microscopic mechanical differences and finely regulate texture properties of different parts of postmortem tan mutton.The longissimus dorsi,biceps and triceps brachii muscles were seperately performed by AFM(atomic force microscope),and combined with SEM(scanning electron microscope)to reveal the microstructure and mechanical differences among different parts of tan mutton.The main results are as follows:(1)The total protein solubility(TPS),myofibrillar protein solubility(MPS),sarcoplasmic protein solubility(SPS),and myofibril fragmentation indices were significantly increased(P<0.05),and drop loss rate(DLR)was significantly increased from Id to 3d(P<0.05),and then decreased significantly from 4th d to 7thd(P<0.05).Hardness,resilience,springiness,gumminess and chewiness variously decreased with different storage time.(2)The stress relaxation parameters obtained from the non-linear fitting of the seven-element Maxwell model showed moderate or higher correlations with the internal quality indices(except for DLR)(R=-0.49-0.87,P<0.01),the TPA indices(except for springiness)had strong positive correlations with E0,E2,E3,?2,?3(r=0.740~0.91,P<0.01).(3)The regression analyses between the stress relaxation parameters and internal quality indices(TPS,MPS,SPS,MFI,DLR),TPA indices(hardness,resilience,springiness,gumminess and chewiness)were carried and verified.MFI,TPS,MPS,SPS,hardness,adhesive and chewiness seven-element Maxwell model all have good prediction performance(R of all verification models are greater than 0.95,t<0.05,tf?13).The seven-element Maxwell model can basically predicte resilience of tan mutton(R and P values of verification model are 0.73,0.18,respectivel,its accuracy and stability are poor),and it can't be used to predicte of DLR.(4)The average Young's modulus E of the longissimus dorsi,triceps and biceps femoris were 195.85±137.98kPa,413.05±644.55kPa,360.12±576.35kPa,respectively.There existed significant differences in microscopic mechanical properties among the above three parts(P<0.05).SEM results showed that triceps muscle fibers were regular,close and orderly.On the contrary,the longissimus dorsi muscle bundles of tan mutton were larger and fibers were loose.The results were consistent with the results of AFM.The results show that there existed significant micromechanical differences among different parts of tan mutton.