Study On The Mechanism Of Heat-Induced Gelation Of Myofibrillar Proteins

Myofibrillar proteins are a group of structural proteins which have the important biological function. It not only participate in sarcous shrinking, affecting sarcous tenderness, but also have consanguineous relationship with rheology, adhesiveness, water-holding capacity(WHC), elasticity, texture of meat products. The quality of meat processing is greatly affected by the water-holding capacity, solubility, dispersing, gelation conformation and emulsification of muscle proteins. Therefore, the research on muscle gelation mechanism and gel properties is the base of gelation controllable technology. At present, the mechanism of heat-induced myosin gelation is clear. However, there is no study on the mechanism of heat-induced gelation of myofibrillar proteins. This study was to investigate the relationship between microstructure and rheology along with gel properties of heat-induced rabbit Pasoas Major (PM) myofibrillar proteins. The aim was to optimize meat processing parameter and guide deep processing of gelation products. The detailed contents and results are showed as follows.1 Observation on microstructure of heat-induced rabbit PM myofibrillar proteins.Microstructure of heat-induced rabbit PM myofibrillar proteins were observed under three conditions.(three conditions:A.25 mmol/L potassium phosphate buffer, pH 6.5 containing 0.6 mol/L KCl. B.25 mmol/L potassium phosphate buffer, pH 6.0 containing 0.2 mol/L KCl. C. dissolved in 25mmol/L potassium phosphate buffer, pH 6.5 containing 0.6 mol/L KCl, then equibibrated to the 25mmol/L potassium phosphate buffer, pH 6.0 containing 0.2 mol/L KCl by 24h dialysis) The result showed that filaments and globular proteins exist at A, only filaments were found at B, while similar configuration were observed at C. it can be concluded that dissolution of myofibrillar proteins at A were better than B. subsequently reduce ionic strength did not disorganize the structures. At three conditions, similar assembling were found with increasing of the temperature, including side-by-side association of filaments and aggregation of globular proteins. When the temperature raised, extensive aggregation occurred. As a consequence, a gel matrix was formed. 2 Rhelogy of heat-induced PM myofibrillar proteins.Storage modulus(G'), thermal transitions, solubility, turbidity of heat-induced PM myofibrillar proteins were tested. The result showed that formation of heat-induced myofibrillar proteins is a sudden mutative process. G', solubility, turbidity remained stable at 20℃～40℃; G'increased rapidly, solubility decline obviously and turbidity ascended slowly from 40 to 47℃; in the temperature zone (within 47-55℃), G'decreased sharply and reached minimum at 55℃, turbidity keep hoist, solubility basically reamained the same,δdropped rapidly from 24°to 7°at 50℃～58℃, means myofibrillar proteins transforming from liquid state to solid gel. DSC thermogram showed transition temperature at 56.10℃; when the temperature raised to 70℃, G'reached a maximum plateau,δshifted to approximately 4°, solubility, turbidity keep stable. Cross-linking interactions of protein polymer subsequently develop highly interconnected and ordered gel network.3 Gel properties of heat-induced PM myofibrillar proteins.The microstructure, gel strength, WHC of heat-induced PM myofibrillar proteins were determined. The result showed that myofibrillar proteins have a strand-type network and globular proteins aggregates at high ionic strength. There was no aperture at 25℃,35℃. The structure was ordered with the temperature increasing. When the temperature raised to 55℃, the structure was symmetrical and compact due to gel network. With increasing of temperature, gel strength increased remarkably, WHC decreased. The molecules remained as coarse and irregular aggregates at low ionic strength, and myofibril fragments assembled themselves before heating after dialysis. Gel strength, WHC at these two conditions were lower than at high ionic strength.