Influence of feeding thermally peroxidized soybean oil to finishing pigs on carcass characteristics, loin quality, and shelf life of loin chops

The objective of this study was to evaluate the effect of feeding soybean oil (SO) with varying levels of peroxidation on carcass traits and shelf life of loins. Fifty-six barrows were randomly assigned to 1 of 4 diets containing 10% fresh SO (22.5 degrees C) or thermally processed SO (45 degrees C for 288 h, 90 degrees C for 72 h, or 180 degrees C for 6 h), each infused with air at a rate of 15 liter/min. Individually housed pigs were provided ad libitum access to feed for 81 d. At 82 d, pigs were slaughtered and hot carcass weight and liver weights were recorded. Carcass characteristics and fresh loin quality were evaluated 1 d postmortem. Loin chops from each carcass were overwrap-packaged and subjected to a 10-d simulated retail display. Daily measurements of L*, a*, b*, reflectance, and visual discoloration were conducted, evaluation of cooking loss and Warner-Bratzler shear force (WBSF) was conducted on chops stored 0, 5, and 10 d, and thiobarbituric acid reactive substances (TBARS) were evaluated on chops stored 0 and 10 d. Shelf life-related data were analyzed as a completely randomized design with repeated measures in time, with storage location (shelf) as a random effect. Carcasses of 90 degrees C pigs weighed 6.0, 8.6, and 6.9 kg less (P < 0.03) than 22.5 degrees C, 45 degrees C, and 180 degrees C carcasses, respectively. Livers of 90 degrees C and 180 degrees C pigs were 14.3% and 11.7%, respectively, heavier (P <= 0.02) than those from pigs fed 22.5 degrees C SO, with livers of 45 degrees C being intermediate. Livers of 90 degrees C pigs represented 0.12 percentage units less (P <= 0.02) of ending live weight than livers of 180 degrees C pigs, and 180 degrees C livers were 0.12 percentage units less (P < 0.01) of ending live weight than those from pigs fed 22.5 degrees C SO, with 45 degrees C being intermediate. There was no difference (P >= 0.19) in back fat depth, loin muscle area, or estimated carcass lean percentage among SO treatments, nor was there an effect (P >= 0.13) of SO on any early post-mortem loin quality traits or loin composition. There was no effect (P > 0.14) of SO on cooking loss, WBSF, L*, a*, b*, hue angle, reflectance, discoloration, or TBARS; however, there was a tendency (P = 0.09) for chops of 45 degrees C pigs to have greater (P < 0.04) chroma than either 22.5 degrees C or 180 degrees C, with 90 degrees C being intermediate. Overall, feeding SO cooked at 90 degrees C for 72 h resulted in reduced carcass weight and dressing percentage; however, there was no evidence that feeding peroxidized SO was detrimental to shelf life of loin chops.