Functional Chicken Muscle Protein Isolates Prepared Using Low Ionic Strength, Acid Solubilization/Precipitation

Full utilization of all the parts of poultry and fish is increasingly becoming an industry goal. Processes such as mechanically deboning are presently used to gain greater yields from whole chickens and fish. The resulting residue from mechanically deboned chicken backs and necks contains between 16-20% protein (Opiacha et al., 1994). If the meat fraction of the residue can be properly separated from the bone it can be utilized as human food. Solubilization of the muscle proteins using either high salt or alkaline conditions and low force centrifugation, has been used by researchers to fractionate the proteins from other components, such as bones (Kijowski and Niewiarowicz, 1985; McCurdy et al., 1986; Opiacha et al., 1994). Recently we (Hultin and Kelleher, 1999) used low pH, low ionic strength solubilization and high force centrifugation to separate fish proteins from head and gutted (bonein) starting material. In contrast to other methods, the high gforce centrifugation was found to substantially reduce the membrane phospholipids while the proteins were recovered in high yields and retained their functionality, especially their ability to gel. Gandemer (1999) recently stated that phospholipids were now widely recognized as the main substrates in muscle tissue for lipolysis and oxidation reactions and responsible for many of the oxidative off odors. Research has also pointed to phospholipids as the potential initiator of lipid oxidation reactions (Love and Pearson, 1971; Meynier et al., 1999). Phospholipid or membrane lipid removal should produce a more stable protein isolate. This manuscript describes a process whereby proteins from two distinctly different types of chicken muscle (breast, mostly light muscle fibers; thigh and leg, mixture of dark and light muscle fibers) were solubilized under conditions of low ionic strength, low pH and recaptured using isoelectric precipitation. Recovered proteins had reduced lipid and phospholipid content and retained the ability to form a gel.