Abstract: The effects of dietary oils and varying cold storage conditions on lipid oxidation in pork were evaluated using 24 finishing pigs (crosses of Large White and Duroc) with an average initial live weight of 54.68?3.12 kg. Pigs were group penned (3 boars and 3 gilts) according to dietary oil treatments but individually fed for 5 weeks. Palm kernel oil (PKO), 0.5:0.5 w/w coconut and palm oils (CPO), palm oil (PMO) and soyabean oil (SBO) were incorporated at 5% into an on-farm diet (based on unconventional feed ingredients, 0.5:0.5 w/w palm kernel cake and rice bran plus 0.5% salt). The resultant diet contained 14.21% crude protein and about 13.05 MJ/kg digestible energy. The backfat thickness (P2) of carcass was measured. Muscle samples were subjected to consistent refrigeration (4?C) and inconsistent refrigeration (simulating power outage) for up to 9 days, and consistent frozen storage (-18?C) and inconsistent frozen storage (thawing once, twice and thrice) for up to 60 days. Oxidation in muscle tissues was also induced by heat. Iodine values of feed and muscle lipids, melting point of subcutaneous fat, moisture, lipid contents and extent of oxidation of muscle tissues were determined. The P2 (10.57?1.71-12.00?1.41 mm), moisture (69.73?1.72- 71.97?0.80%) and lipid (10.23?0.85-11.05?1.01%) contents of muscles were not significantly influenced (P>0.05) by dietary treatments. Levels of unsaturation, measured as iodine values were 41.42 ?1.16, 45.98?0.78, 53.70?1.42 and 78.26?2.01 (P<0.001) for dietary lipids and 17.96?0.25, 22.01?0.27, 23.00?0.22 and 26.44?0.20 (P<0.001) for muscle lipids, for PKO, CPO, PMO and SBO based diets, respectively. Subcutaneous fat melting point decreased with increased unsaturation of dietary lipids (28.23?1.92, 26.50?0.68, 25.85?1.32 and 23.08?1.36, P<0.01 for pigs fed PKO, CPO, PMO and SBO based diets respectively). Muscle tissues from pigs fed PKO diet was most stable to lipid oxidation during refrigerated and frozen storage as well as heat-induced lipid oxidation. This was followed by those from pigs fed CPO and then PMO diets (P<0.05). Muscle tissues from pigs fed SBO diet was most susceptible to lipid peroxidation. Thiobarbituric acid reactive substances (TBARS) contents of muscle lipids increased with increasing length of refrigerated storage irrespective of dietary treatments. TBARS concentrations of muscles stored under consistent refrigeration and frozen storage conditions were lower than those stored under inconsistent conditions. TBARS contents of muscle tissues that were frozen consistently and those thawed once were not significantly different (P>0.05) and were significantly lower (P<0.05) than those thawed twice and thrice. Oxidative susceptibility of muscle tissues increased with increasing unsaturation of muscle lipids (muscle from SBO > PMO > CPO > PKO diets) following heat-induced lipid oxidation.
G.E. Onibi and O.O. Atibioke , 2004. Infuluence of Dietary Oils and Cold Storage Conditions on Oxidative Stability of Pork . Journal of Animal and Veterinary Advances, 3: 1-8.