Role of Chicken Breast Muscle Proteins in Meat Emulsion Formation: Natural Actomyosin, Contracted and Uncontracted Myofibrils

Natural actomyosin (NAM) and glycerinated myofibrils (contracted and uncontracted) from chicken breast muscle were taken to 0.6M NaCl, 20 mM citrate‐phosphate buffer (pH 7), and tested for emulsifying capacity (E.C.) and timed emulsification. Myofibrils were extracted for 0, 1, and 24 hr in the buffer prior to testing. The aqueous phase was separated by centrifugation and analyzed quantitatively by SDS gel electrophoresis. The E.C. of NAM was lower than that reported earlier for myosin, but was equal to it with added ATP or pyrophosphate. The E.C. of myofibrils varied considerably depending upon whether the 0.6M NaCl soluble protein or the initial protein concentration was used as the denominator. Timed emulsification studies showed that actomyosin was removed from solution in a manner similar to myosin alone. However, when this complex was dissociated, actin remained in the aqueous phase, while myosin was preferentially used in the emulsion. The same relationship was displayed in myofibrils. The regulatory proteins tropomyosin and troponin exhibited a behavior independent of both actin and myosin. Tropomyosin always increased in the aqueous phase relative to myosin regardless of the presence or absence of ATP, while the troponins were more readily removed from solution in the presence of ATP.