Study On Rheological Properties Of Rabbit Skeletal Myosin Under Different Conditions

The mechanism and property of heat-induced gel of myosin is the theoretical and fundamental basis for meat scientists designing food formula, improving technological parameters and manufacturing meat related products with high quality. Previous studies only focused on the rheological properties of myosin, while barely on the relationship between the rheological parameters and processing conditions. In this study, myosin were extracted and purified from the Pasoas Major (PM) and Semimembranousus Proprius (SMp) of 3-months old male New Zealand rabbit skeletal muscles. The static viscoelsaticity and dynamic viscoelasticity of myosin under different conditions were tested in order to find the functional relationship between technological parameters and processing conditions, which can provide theoretical bases for the further processing of gel meat products. The detailed contents and results are shown as follows.1. The static viscoelsaticity parameters of myosin were tested under different shear rates,protein concentrations,KCl concentrations and pH values. K (viscosity coefficient), n (flow index) and Ea (activation energy) were got which can tell the internal characteristics of myosin according to power law, or Arrhenius equation by Matlab2007a. The results showed that under different conditions, the myosin solution is non-Newtonian fluid, and the relationship betweenτ(sheer stress) and 8 (sheer rate) could be explained by the power functionτ=K·δn. All values of n (flow index) were smaller than 1, which means the myosin solution was pseudoplastic fluid. K and n were affected by protein concentration,temperature,pH value and KCl concentration. Accordingly, the relationship between n (flow index) and protein concentration can be described by K=1.08×10-2C2-0.15C+1 for PM myosin, and K=9.86×10-3C2-0.15C+1 for SMp myosin. When the temperature goes above 25℃, the myosin have aggregated, and the mathematical model for the influence of temperature on n (flow index) could be , then the Ea (activation energy) of PM myosin can be obtained as 26250 J/mol, which was much larger than that of SMp myosin (20090J/mol), and this explained the reason for the gel strength formed by white muscle larger than that by red muscle. The static viscoelsaticity parameters of PM and SMp in our research appear to have analogous changes after the treatment.2. The dynamic viscoelasticity parameters of heat-induced gel of myosin were tested under different protein concentrations,KCl concentrations,pH values and heating rates to discover the process of myosin gelation. The results showed that the protein concentration exerted significant influence on the heat-induced gel of myosin. Myosin can not form gel when the protein concentration was lower than 5 mg/ml. The protein molecules interacted when protein concentration went higher than 5 mg/mL, then formed gel by heating and a number of chemical bonds. Larger protein concentration brings more intense interaction, causing a greater G'(storage modulus). KCl concentration and pH value can change the distribution of branched electric charges of the amino acids, leading to the property of myosin in the solution, which will change the interaction between proteins, and finally influence the property of gel. The gel strength appears much higher under a relatively low concentration of KCl (0.1 mol/L and 0.2mol/L) than that under a high concentration. The gelation of myosin was significantly affected by pH value. The gel will form more strongly with the solution closer to the isoelectric point. The strength of heat-induced gel was affected by heating rate. A relatively better gel product will be obtained under a relatively low heating rate in the process of meat production. Three temperature transition points of G'are shown during heating, and the gel strength of PM myosin is much stronger than that of SMp myosin. The 3-order Gaussian distribution can perfectly describe the relationship between G'and temperature, and the surface model can directly tell the relationship between G'and different processing conditions. The dynamic viscoelasticity parameters of PM and SMp myosin in our research appear to have analogous changes after the treatment.To sum up, rheological properties of myosin are affected by different processing conditions. Relationship among parameters can be expressed by suitable functions. Myosin solution is pseudoplastic fluid under different conditions. The rheological properties of PM and SMp myosin in our study appeared to have analogous changes after the treatment.