Fatty acid composition and oxidation in beef muscles as affected by ageing times and cooking methods.

This study aimed to determine how ageing and cooking, each one applied to the beef meat most suitable (pan-fried or grilled ribeye steak, braised chuck and fried or roasted rump steak), induce changes in lipid content, fatty acid (FA) composition and lipid oxidation of muscles from 16 cattle representative of animals raised for France meat production. The fattiest muscle (ribeye) was the richest in saturated and monounsaturated FA leading to poor nutritional indexes. In contrast, the leanest muscle (rump) had the highest proportion of polyunsaturated FA and the highest levels of peroxidation without exceeding critical limits. The impact of cooking methods seemed mainly linked to the moisture loss increasing meat fat content and the culinary fat addition whose FA composition marked the meat. Cooking methods induced oxidation phenomena that could exceed the limit thresholds. In conclusion, short cooking time of rump steak was the best combination to meet nutritional expectations.

Impact of reducing nitrate/nitrite levels on the behavior of Salmonella Typhimurium and Listeria monocytogenes in French dry fermented sausages.

Salmonella and Listeria monocytogenes are two pathogenic bacteria that most frequently contaminate pork meat. In dry fermented sausages, several hurdles are used for controlling bacterial growth such as nitrite and salt addition. In Europe, practices consist of adding potassium nitrate (250ppm expressed as NaNO3) or a combination of nitrate/nitrite (150/150ppm expressed as NaNO3/NaNO2 respectively). However, involvement of these additives in nitrosamine formation is a matter of concern. Consequently, a decrease in nitrite/nitrate amounts is proposed. The aim of this study was to evaluate the impact of reducing levels of these additives on Listeria and Salmonella behavior. Using challenge-tests, five trials were carried out by varying the concentration of nitrate and nitrate/nitrite. Results shown that nitrite is a relevant hurdle for control Salmonella and Listeria. At the end of drying, the most significant reductions of pathogens are obtained in sausages with nitrite added at the both tested concentrations (120 or 80ppm NaNO2).

Quantitative study of the relationships among proteolysis, lipid oxidation, structure and texture throughout the dry-cured ham process.

Temperature, salt and water contents are key processing factors in dry-cured ham production. They affect how proteolysis, lipid oxidation, structure and texture evolve, and thus determine the sensory properties and final quality of dry-cured ham. The aim of this study was to quantify the interrelationships and the time course of (i) proteolysis, (ii) lipid oxidation, (iii) five textural parameters: hardness, fragility, cohesiveness, springiness and adhesiveness and (iv) four structural parameters: fibre numbers, extracellular spaces, cross section area, and connective tissue area, during the dry-cured ham process. Applying multiple polynomial regression enabled us to build phenomenological models relating proteolysis, salt and water contents to certain textural and structural parameters investigated. A linear relationship between lipid oxidation and proteolysis was also established. All of these models and relationships, once combined with salt penetration, water migration and heat transfer models, can be used to dynamically simulate all of these phenomena throughout dry-cured ham manufacturing.

Plant extracts combined with vitamin E in PUFA-rich diets of cull cows protect processed beef against lipid oxidation.

The effect of supplementing PUFA-rich cull cow diets with vitamin E (2.8 g/animal/day) or vitamin E plus plant extracts rich in polyphenols (PERP) (126 g/animal/day), for 101+/-3 days preceding slaughter, on the oxidative stability of longissimus thoracis (LT) and semitendinosus (ST) steaks was evaluated after ageing (for 12 d at 4 degrees C either in carcass or under-vacuum) and packaging (14 d under-vacuum (V), 4 d aerobic (A) and 7 d under modified atmosphere (70:30, O(2)/CO(2)) (MA)). The ageing method had no effect on a beef lipid oxidation intensity marker (malondialdehyde (MDA)), whereas packaging systems containing O(2) (A and MA) significantly increased lipid oxidation intensity (5 and 13 times higher than under V, respectively). Adding antioxidants to diets of animals given a PUFA-rich diet significantly improved lipid stability in steaks; the combination of vitamin E and PERP was more efficient than vitamin E alone for the most deleterious beef packaging.