Effects Of Temperature On Myosin Aggregation During Duck Roasting Process

Crispy skin and tender meat are the characteristics of Beijing roasted duck.The formation of meat tenderness is closely related to thermal myosin gel.The thermal aggregation of myosin is the key to the quality of Beijing roast duck.In order to analyze the effect of heating on the aggregation of myosin in the traditional roasting process,the breast and thigh meat of Beijing ducks was chosen as the material in this study to analyze the types of muscle and properties of thermal myosin gel after being purified.With simulation of the traditional roasting process,the effect of heating rate and temperature on myosin gel properties was studied.The effect of temperature on the characteristic structure,chemical force and domain of duck myosin was studied by using computer software to simulate the traditional roasting temperature.The results are as follows:（1）The property that high content of type II muscle fiber in Beijing ducks leads to the high strength of myosin gel was clarified.Beijing duck’s breast and thigh meat contained mainly type II and type I muscle fibers separately,and the strength and water holding capacity of breast muscle myosin gel were significantly higher than those of thigh meat（P<0.05）.The myosin gel strength of duck breasts rose to72.56 g（P<0.05）at 30 days of age and then decrease with the increase of age.The water holding capacity kept a similar trend with gel strength.The peak value reached 45.71%at the age of 30 days（P<0.05）.The strength of myosin gel of the 46-day-old thigh muscle was the highest,reaching 63.06 g（P<0.05）,but the gel water holding capacity was the lowest,was 32.04%（P<0.05）.（2）The regulation that the myosin of duck meat formed dense network structure in traditional roasting process and then formed its unique texture was defined.The strength of Beijing duck breast muscle myosin gel at 90 and 100℃was significantly higher than that of 80℃（P<0.05）;the myosin gel at 100℃was more compact than that of other temperatures with smaller and more uniform pore;the content of immobilized water was high while free water was low,and was significantly different from that obtained at a linear heating rate of 2.5℃/min（P<0.05）.（3）The regularity of myosin denaturation at 45-50℃,aggregation at 55℃and aggregation stability at 80℃under the traditional roasting mode were studied.At 45-50℃,Ca²⁺-ATPase activity and total sulfhydryl content of myosin began to decrease from 0.22 to 0.89 significantly（P<0.05）,while the turbidity increased significantly.At this time,myosin began to disintegrate and denature.When Ca²⁺-ATPase was deactivated at 55℃,the total thiol content reached the maximum 19.38 mol/10⁵g,and the hydrophobicity of the surface decreased significantly.At this time myosin began to aggregate.The aggregation became stable at 80℃.（4）The molecular process of myosin hydrophobic group exposure and hydrophobic interaction promoting the formation of aggregates under the traditional roasting mode were analyzed.At 50℃,the bond energy of myosin MHC was the lowest,which was 694.10 kcal/mol;at 55℃,the electrostatic energy of myosin tail was reduced to-84441.9 kcal/mol.at this time,the structure of myosin was unstable,which may be related to the denaturation temperature of myosin;at 80℃,the kinetic energy and total energy consumed by myosin interaction are more,which are-73338.3 kcal/mol and 21151.8 kcal/mol,respectively,the structure of myosin was unstable;at 80℃,the hydrophobicity of protein aggregation was high,which can promote protein aggregation;at 40℃,50℃,the content of myosin ion bond and hydrogen bond was high,at 80℃,the hydrophobicity was strong,and at 100℃,the content of disulfide bond was the highest,which was easier to promote the aggregation of myosin.