Warmed-over flavour in chill-stored pre-cooked pork patties in relation to dietary rapeseed oil and vitamin E supplementation
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Lean pork patties were produced from the longissimus dorsi muscle of pigs fed either (1) basal feed containing 3% fat without vitamin E supplementation (Control), (2) basal feed enriched with 6% rapeseed oil (canola) without vitamin E supplementation (RAP), or (3) basal feed enriched with 6% rapeseed oil and 200 mg vitamin E as all-rac-α-tocopheryl acetate/kg feed (RAP-E). Enrichment of the pig diet with rapeseed oil slightly increased the content of monounsaturated and polyunsaturated fatty acids and slightly reduced the amount of saturated fatty acids in the products, although the difference was not statistically significant. The fat content in non-cooked patties was found to be similar for the three products, as was the level of secondary oxidation products determined as headspace hexanal and thiobarbituric acid reactive substances (TBARS), whereas the content of vitamin E as α-tocopherol was found to be significantly different. α-Tocopherol levels in non-cooked patties reflected dietary vitamin E levels and were: Control [2.33 mg α-tocopherol/kg dry matter (DM)] <RAP (3.31 mg α-tocopherol/kg DM) <RAP-E (6.26 mg α-tocopherol/kg DM). Heat treatment of patties resulted in a 26–28% decrease in α-tocopherol content and degradation continued during chill storage (5 °C). The degradation of α-tocopherol was found to be proportional to the initial level, and the levels in pre-cooked patties were still related to dietary vitamin E levels after 4 days of chill storage. Development of warmed-over flavour in pre-cooked patties during chill storage, as followed by determination of hexanal and TBARS and by descriptive sensory analysis showed that (1) feeding pigs a level of 6% rapeseed oil increases the susceptibility of pre-cooked patties to lipid oxidation during chill storage, and (2) that supplementation of 200 mg vitamin E/kg feed effectively counteracts the effects of the rapeseed oil on lipid oxidation.
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