Oxidation of lipids and proteins in frankfurters with different fatty acid compositions and tocopherol and phenolic contents

Abstract

Lipid and protein oxidation and the stability of heme iron (HI) in refrigerated frankfurters (60 days/4 °C) were studied. Lipid oxidation was evaluated as TBA-RS and hexanal counts isolated with solid-phase microextraction (SPME), whereas protein carbonyls groups were quantified by following the DNPH coupling method. Frankfurters were produced using meat and fat from either extensively reared Iberian pigs (IF) or intensively reared white pigs (WF). Hybrid frankfurters (HF) manufactured with meat from white pigs and fat from Iberian pigs was also considered. Frankfurters had significantly different vitamin E and total phenolic contents with the IF having the highest antioxidant content, followed by HF and WF. Compared to WF, IF had significantly higher amounts of monounsaturated fatty acids (MUFA) and smaller of saturated (SFA) and polyunsaturated fatty acids (PUFA). HF presented an intermediate fatty acid composition between IF and WF. Results suggest an intense oxidative deterioration of frankfurters during refrigeration since PUFA were gradually degraded while oxidation products, such as TBA-RS and hexanal, were generated. Proteins were also damaged, since carbonyls derived from their oxidation and non-heme iron content increased during refrigeration, also suggesting oxidative instability of the heme molecule. IF showed a higher oxidative stability compared to WF, which could be explained by the different fatty acid composition and antioxidant status. Using fat from Iberian pigs for the production of HF improved the oxidative stability of frankfurters, with that being significantly higher than those from WF and IF. IF had a significantly higher amount of iron than had WF and HF which could have played a important role in the development of the oxidative reactions. Significant correlations were established between protein and lipid oxidation and protein oxidation and heme degradation, suggesting likely interactions between such processes.