Changes in fatty acids and polar material of restructured low-fat or walnut-added steaks pan-fried in olive oil

The study aims to determine the influence of pan-frying on the fatty acid composition and fat content and alteration of functional restructured beef steaks. Low-fat (L, 2% fat), 20% walnut-added (W, 13% fat) and medium fat (M, 13% fat) steaks were prepared and fried in extra virgin olive oil. Pan-frying increased fat in L and W steaks and decreased it in M ones. Raw L and M steaks showed similar fatty acid profiles while W ones contained a lower percentage of saturated fatty acids (SFA) and monounsaturated fatty acids (MUFA) but a higher percentage of polyunsaturated fatty acids (PUFA). The fatty acid profile of fried steaks was between that of the raw steaks and olive oil. Several fatty acids (g fatty acid/100 g edible steaks) were affected (p < 0.001) by the frying × meat-formulation interaction. Linoleic and linolenic acid contents did not decrease in fried W steaks, but decreased (p < 0.05) when data were expressed on a dry matter basis.Frying increased SFA, MUFA and ω-6 PUFA contents in L samples while it decreased SFA and increased ω-6 PUFA in M steaks. Before and after frying, W steaks had atherogenic and thrombogenic indexes at least three times lower than their counterparts. Both indexes decreased in fried L samples while only the AI in M ones. Polar material content (PM) increased only in L samples. No relevant differences were found between PM of the fried steaks and that of their corresponding used oils. Results suggest that pan-frying improves the fatty acid composition of L and M steaks with minor changes in PM. The high retention of lipids observed in the W samples permits consumption of ω-3 PUFA- and ω-6 PUFA-enriched meat with a very low content of alteration compounds.     

Effectiveness of rosemary essential oil as an inhibitor of lipid and protein oxidation: Contradictory effects in different types of frankfurters

The effect of increasing levels (150, 300 and 600ppm) of rosemary essential oil on lipid and protein oxidation and the increase of non-heme iron (NHI) content during refrigeration (+4°C/60 days) of frankfurters produced with tissues from Iberian pigs (IF) or white pigs (WF), was studied. Frankfurters with no added essential oil were used as controls. Iberian pigs were free-range reared and fed on acorns and pasture whereas white pigs (Large-white×Landrance) were intensively reared and fed on a mixed diet. Large differences were detected between types of frankfurters (Iberian vs white) in terms of fatty acid composition and tocopherols content due to the different feeding background of the animals. The effect of the addition of rosemary essential oil on the oxidative stability of frankfurters depended on the level of added essential oil and the characteristic of the frankfurter. The rosemary essential oil successfully inhibited the development of lipid and protein oxidation in IF with that antioxidant effect being more intense at higher concentrations of essential oil. In WF, 150ppm rosemary essential oil showed an antioxidant effect, significantly reducing the generation of lipid and protein oxidation products. At higher levels (300 and 600ppm) the essential oil had, in general, no effect on lipid oxidation while significantly enhanced the oxidation of proteins and the release of iron from myoglobin. The presence of certain amounts of tocopherols in the frankfurters could have influenced the activity displayed by the added essential oil leading to antioxidant or prooxidants effects though the different fatty acid composition and oxidative status between frankfurters could also have had an effect.