COLOUR, LIPID AND PROTEIN OXIDATION IN BREAST AND THIGH MEAT OF BROILERS RAISED IN FOUR PRODUCTION SYSTEMS IN BELGIUM Zeshan Ali*, Eline Kowalski and Stefaan De Smet Laboratory for Animal Nutrition and Animal Product Quality, Department of Animal Sciences and Aquatic Ecology, Ghent University, Belgium *Corresponding author email: Zeshan.Ali@ugent.be I. INTRODUCTION Worldwide, broilers are raised in different production systems from extensive to intensive, covering a range of genetics and management practices. Influence of the production system on the oxidative stability of meat has not been widely studied [1]. Oxidation of myoglobin, lipids and protein are major causes of quality deterioration in meat [2]. Differences in in vivo and postmortem muscle metabolism may affect the endogenous antioxidant defense system and the release of pro-oxidants and reactive oxygen species, resulting in potential differences in resistance against oxidation. The main objective of the present study was to compare oxidation in breast and thigh meat from broilers produced in four divergent production systems in Belgium. II. MATERIALS AND METHODS In this study, 4 broiler production systems with distinctive characteristics (Intensive, Better Chicken Commitment (BCC), Slow growth with outdoor access and Organic) were selected (Table 1). From each production system, 5 farms randomly distributed in the country were chosen, and 15 broilers (mixed sex; 3 broilers per farm) were slaughtered and sampled. On day 2 after slaughter, the meat from the thigh and breast muscles (skinless) was minced and approximately 40 g was placed in petri dishes. These petri dishes were covered with a foil to limit dehydration and exposed to light (1600-2200 lux) for 7 days in the fridge at 2-4 °C. Colour lightness (L*), redness (a*), and yellowness (b*) were measured daily in duplicate with a Hunterlab Miniscan colour meter (D65 light source, 10° standard observer, 45°/0° geometry, 1-inch light surface, white standard) to estimate colour stability. The difference (day1 – day7) in colour lightness (ΔL), redness (Δa), yellowness (Δb) and total colour difference ΔE (ΔE = [(ΔL)2 + (Δa)2 + (Δb)2]1/2) was calculated for this purpose. On day 7, the samples were vacuum packed and frozen at -80°C for analysis of lipid and protein oxidation. Lipid oxidation was assessed in duplicate, spectrophotometrically by the thiobarbituric acid reactive substances (TBARS) method based on Tarladgis et al. [3] and expressed as malondialdehyde (MDA) in µg per g meat. Protein oxidation was measured in duplicate through the formation of protein carbonyls compounds (PCC), according to the method of Oliver et al. [4] with some modifications by Ganhao et al. [5]. PCC were determined spectrophotometrically, following their covalent reaction with 2,4- dinitrophenylhydrazine (2,4-DNPH), and expressed in nmol carbonyls per mg protein. Table 1 Summary of production characteristics This data was summarized from 18 farms sampled so far (Intensive, Slow growth and Organic n=5 each, and BCC n=3) *Outdoor access was temporarily not possible due to avian flu. Intensive BCC Slow growth Organic Breed Ross 308 RedBroM Ja 757 Ruby XL (SASSO) Age at slaughter (days) 39-42 42-45 56 73-76 Live weight at slaughter (kg) 2.6-2.8 2.4-2.6 2.1-2.3 2.3-2.5 Stocking density (kg/m2) 42 30 27-33 21 Outdoor access No No Yes (limited)* Yes*