Effect of dietary fats and antioxidants on the frozen storage life of cooked pork products

The objectives of this study were: 1) to investigate the oxidative stability of bacon manufactured from pork obtained from pigs fed a diet containing a combination of vitamin E (10 mg or 200 mg α-tocopheryl acetate per kilogram of feed) and fishmeal (0% or 5%) and processed with wood smoke only or with a combination of liquid smoke and wood smoke, 2) to investigate the oxidative stability of wiener sausages prepared from pork obtained from pigs fed a diet containing a combination of vitamin E (10 mg or 200 mg α-tocopheryl acetate per kilogram of feed) and fishmeal (0 % or 5%) and manufactured with or without an antioxidant (0.03% rosemary extract or 2.5% whey powder). Twelve (Large White x Landrace) gilts were randomly allotted to four dietary treatments containing two levels of vitamin E (10 or 200 mg/kg feed) and two levels of fishmeal (0 or 5%). Two products were manufactured from meat obtained from the animals after slaughter, bacon with or without liquid smoke and wiener sausages with or without rosemary extract and sweet whey powder. The oxidative stability of bacon was examined over 16 weeks of frozen storage and that of wieners during ten months frozen storage. Lipid oxidation in the products was measured by means of thiobarbituric acid reactive substances (TBARS), fluorescence shift and sensory evaluation. The fluorescence shift method was unsatisfactory in the case of wieners, as it appeared that rosemary extract contained compounds that fluoresced and therefore interfered with the method. The fatty acid composition of bacon fat showed that diet had no significant effect (P > 0.05) in the proportions of total saturated and total monounsaturated fatty acids. Bacon prepared from pigs fed the diet supplemented with vitamin E had higher levels (P < 0.05) of total polyunsaturated fatty acids than bacon manufactured from pigs fed the other experimental diets. Analysis of vitamin E content in bacon fat and muscle showed that the diet supplemented with 200 mg vitamin E per kilogram of feed increased α-tocopherol levels by 3 fold in bacon fat and by 2 fold in bacon loin muscle compared to bacon prepared from pigs fed a basal level of vitamin E (10 mg vitamin E per kilogram of feed). Bacon processed with a combination of liquid and wood smoke proved to be significantly less (P < 0.001) susceptible to lipid oxidation compared to bacon processed with wood smoke only. It was observed that dietary supplementation of fishmeal produced adverse effects on lipid oxidation in bacon, while dietary supplementation of vitamin E was shown to help reduce lipid oxidation in bacon whether fishmeal was present in the diet or not. Lipid oxidation in frozen bacon was most successfully reduced when bacon was manufactured from pigs fed a diet supplemented with 200 m g of α-tocopherol per kilogram of feed and processed with a combination of liquid and wood smoke. This trend was also observed in bacon manufactured from pigs fed fishmeal and vitamin E and processed with the combination of liquid and wood smoke. Sensory evaluation showed a slight increase in oxidation with time but no overall differences were observed between the dietary treatment groups. No lipid oxidation as measured by TBARS, fluorescence shift and sensory analysis was observed in wieners stored at -20°C for ten months. The wieners were unaffected (P > 0.05) by dietary treatments or by the addition of antioxidants. Dietary vitamin E appeared to lower TBARS values, suggesting vitamin E helped retard lipid oxidation. The low TBARS, fluorescence shift levels and sensory scores obtained for wieners containing whey powder showed that slow lipid oxidation was taking place. A similar trend was observed with rosemary extract. The high oxidative stability of the wieners, even in the absence of antioxidants could be due to the presence of sodium erythorbate in the formulation as an additional antioxidant.