Effects Of Heat Treatment On Duck Meat Tenderness And Its Mechanism

The eating quality of meat has a large effect to determine the trends of consumer consumption and the trends of producer’s production. The tenderness is affected mostly by the two main components namely myofibril and connective tissue, the former formed the actomyosin toughness, while the latter formed the background toughness. Meat normally undergoes heat treated before eating, during heat process, the meat protein denatured, causing structural changes of meat, and finally impact on tenderness. In this research, duck meat was used as material to study changes of duck meat tenderness during water bath cooking and changed in myofibril and connective tissue and their contributing to tenderness by SEM, TEM, TPA, SDS-PAGE, etc., the dissociation of acotomyosin and its relationship with tenderness is also investigated, in order to Provide theoretical guidance for duck production and processing. A total of four parts are including in this study, the details as follow:1change of duck meat tenderness with different final internal temperature and its mechanismsIn this study, the dynamic process of the duck meat cooking up to100℃, and changes in myofibril and connective tissue are investigated. The results showed that:with increasing internal temperature, the shear force value gradually increased, accompanied by increasing cooking loss. The change of shear force is found to increase in two stages. The first stage is below50℃(P<0.01), the second stage is60-95℃(P<0.01), and between50-60℃the shear force get a reduction process. With increasing temperature, the myofibrillar protein solubility decreased (P<0.01). the decrease was found most significant in70-80℃(P<0.01). in the meanwhile, the structure of myofibrillar contraction, shortening of muscle fiber diameter occurred (P<0.01), the most severe contraction in the muscle fiber diameter is40-50℃and70-80℃(P<0.01). sarcomere length signifiantly decreased (P<0.01),however with a temporary increase between50-60℃. Collagen solubility significantly increase after cooked to70℃(P<0.01)and reached the highest point at80℃, but decrease with higher temperature(P<0.01). Perimysium and endomysium structure continues to receive damage, the phenomenon of granulation occurred. Correlation analysis showed that the shear force significant correlated with cooking loss, myofibrillar protein solubility and sarcomere length are very (P<0.01), but not significant with solubility of collagen, muscle fiber diameter (P>0.05). The results suggested that internal temperature has a large impact on tenderness; change of tenderness is showed in increase in two stages. Changes in myofibril contribute to both stage of toughness; changes of connective tissue main contribute to the first stage of toughness, at temperature higher70℃, in contributes to improve tenderness.2changes of duck meat tenderness during different retention and its mechanismsThis study investigated the changes of tenderness, myofibril and connective tissue when duck meat was holding for different time (0,10,30,60min) at different temperatures. The results showed that:with increasing holding time, at60℃,the shear force has a downward trend(P>0.05); at80℃, there is no apparent changes in shear force value(P>0.05); at100℃, the shear force significantly decreased(P<0.01). with increasing holding time, at60and80℃, cooking loss significantly increased (P<0.01)at100℃, the cooking loss reached the highest point, and no apparent changes with holding time(P>0.05). With increasing temperate and holding time, the myofibrillar protein solubility decreased, cause shrinkage of myofibrils and thereby the structure. At60℃, the myofibrillar solubility significantly decreased(P<0.01), the fiber diameter increase in trend (P<0.05), sarcomere length also increased in trends(P<0.05); At80and100℃, the myofibrillar protein solubility reached its lowest point and showed non apparent change with holding time(P>0.05), the fiber diameter gradually decrease (P<0.01). At80℃, sarcomere length decreased with increasing time(P<0.01); At100℃, no apparent changes occur(P>0.05). The shear force is significantly correlated with cooking loss, sarcoplasmic protein solubility, sang fiber diameter (P<0.05). Cooking loss significant correlated with fiber diameter (P<0.05), and highly correlated with myofibrllar protein solubility, collagen solubility and sarcomere length (P<0.01). The results suggested that:with increasing holding time, the tenderness improved, myofibrillar protein solubility decreased in trends, collagen solubility increased in trends, structure of parimysium and endoumysium destroyed and granulated. Both myofibril and connective tissue affect the final meat tenderness.3the effects of heat treatment on dissociation of actomyosin of duck meatThis study determined the dissociation of actomyosin during cooking process, and explores the factor that affects dissociation. The results showed that at40℃, compared with the control group, the actin protein band had no significant change; at50℃for10min, the actin bond density significantly increased and still significantly higher than the control. At60℃, the results were similar with that at50℃, from30-60min, actin bond concentration decreased in trends; At70℃,80℃,100℃, no actin bond was found. In general, actin bond occurred mainly between50-60℃, it was no apparent changed in actin bond density below50℃, and no actin bond occurred higher than70℃. Quantity analysis of actin bond between50-60℃showed that, the actin bond density significantly higher compare to the control, with increasing time the actin bond density decreased in trends. At4℃, In actomyosin treated with8mM or16mMAMP or IMP, the actin bond density increased significantly compare to the control; At60℃, actin bond density in actomyosin treated with16mM AMP or IMP significant increased compare to the control. In actomyosin treated with8mM or16mM ATP, actin bond density significant lower compare to the control(P<0.05) at4℃and60℃. The results suggest that, dissociation of actomyosin mainly occurred between50-60℃, and the dissociation maybe reversed, at higher temperature, actomyosin seemed denaturized without dissociation. AMP and IMP could be contributing to dissociation of actomyosin.4The effect of staged cooking duck meat tenderness and its relations to dissociation of actomyosinThis study investigated the change of myofibril and connective tissue structure and its relationship with tenderness. The results showed that, at endpoint70℃, the three-stage cooking significantly lower shear force(P<0.05), at endpoint80and90℃, the shear force still decrease in trends(P>0.05); the two-staged cooking also decrease shear force in trends at endpoint70℃, but significant increase shear force at endpoint80、90、95℃(P<0.01). Compare to the convention cooking, the three-staged cooking have no apparent different in the light value, red value, and yellow value (P>0.05) at each endpoint temperature. The two-staged cooking significant lower the light value at each endpoint temperature (P<0.01), significant increase the red value (P<0.01), and no apparently changes in yellow value (P>0.05). at endpoint70℃, compare to convention cooking, the sarcomere length by the three-staged or two-staged cooking significant increased(P<0.01), the fiber diameter decreased in trends(P>0.05), and connective tissue by the three-staged cooking destroyed more severe; at each endpoint temperature, compare with convention cooking, the collagen solubility by two-staged cooking has no apparent deference(P>0.05), the three-staged cooking decreased collagen solubility intends, however, no statistical signifier was found (P>0.05). The results suggest that, at endpoint70℃, compare to convention cooking, the staged cooking could be improve tenderness of duck meat, this is found in relationship with the restrict of myofibril shrinkage. The three-staged cooking was a better cooking regime compare to convention cooking, as it improved tenderness without negatively affect meat color and cooking loss.Taken all the results in account, both the internal temperature and Holding time significant affect duck meat tenderness, and the myofibrillar and connective tissue structure, the net effect of the two components caused the final tenderness of duck meat. The staged cooking caused dissociation of actomyosin and destroys of connective tissue, increase collagen solubility; all these could improve duck meat tenderness.