Liberation of actin from actomyosin in meats heated to 65 °C

This study investigated whether actin liberation from myofibrils occurs during the heating of various muscles, as well as squid mantle muscle at temperatures, such as 60 °C, employed for vacuum cooking of meats. Actin liberation was demonstrated in scallop striated adductor muscle, but not in beef, pork, or chicken, using the detection method previously employed with squid muscle, in which liberated actin was detected with SDS–PAGE, in the supernatant obtained by centrifugation of the homogenate of heated muscle in 0.2 M KCl at a neutral pH. However, actin liberation was demonstrated in beef, pork and chicken by a new detection method, in which heated muscle was homogenized in 0.6 M KCl or NaCl at a slightly alkaline pH and maintained at 4 °C for 16 h with stirring, after which the homogenate was diluted three times with water and centrifuged to obtain the supernatant containing the liberated actin. This new method indicated that actin liberation in beef, pork, and chicken was marked by heating at 65 °C, but scarcely induced at 80 °C. Thus, the liberation of actin from myofibrils may contribute to the greater tenderness of vacuum-cooked meat (meat heated at a low temperature for long time), as compared with meat prepared by cooking at a higher temperature.