Loss of sensory quality in muscle foods is often caused by lipid oxidation, which can be inhibited by the use of antioxidants. Because of health concerns of synthetic antioxidants, there has been an increasing demand for natural antioxidants. Phospholipase A2 (PLA2), a lipolytic enzyme that hydrolyzes phospholipids, was linked to increased oxidative stability of frozen cod muscles (Castell & Bishop, 1969). Therefore, PLA2 could be an alternative natural antioxidant from pancreas, an animal by-product, which serves as an excellent source for the enzyme. However, information on the effect of PLA2 from pig pancreas on lipid oxidation in poultry and pork are still lacking.
The effect of PLA2 (10 mg/kg muscle) was tested independently in cod fillet, chicken (thighs and drumsticks) and pork (semitendinosus) muscles by adding different pro-oxidants. The muscles were prepared by cutting and grinding through a 5-mm plate. Additionally, ground chicken and pork were minced using a Waring blender. Hemoglobin (Hb) was added to ground cod muscle to stimulate lipid oxidation due to low levels of endogenous heme proteins, potent promoters of lipid oxidation in fish. For pork, instead of hemoglobin, NaCl was added at 1.5 percent by weight to promote lipid oxidation. In contrast, no exogenous pro-oxidant was added into minced chicken since lipid oxidation occurs readily. In all cases, control samples were treated with deionized water instead of PLA2. Ground muscles were separately stored in amber-colored glass bottles and stored on ice (0.2°C) in order to minimize microbial growth and to allow lipid oxidation to proceed at an optimal rate for sampling. Lipid oxidation was measured as peroxide value (PV) and thiobarbituric acid reactive substances (TBARS). The experiment design was completely randomized design (n = 3) with repeated measurements and data were analyzed using SAS.