Comparison of meat quality traits among the main chicken categories marketed in Italy: 2. lipid and protein oxidative stability

This study aimed at evaluating the effect of the market category, defined according to the farming system (conventional indoor - C, free-range - F, and organic - O) and carcass weight (light – L,1.8-2.0 kg used for rotisserie products, medium – M, 2.5-2.8 kg used for producing cut-ups, and heavy – H, used for producing cut-ups or processed products), on the oxidative status of breast and thigh meat. A total of 625 breast fillets (N=25/flock) and 500 thighs (N=20/flock) were selected 3 h post-mortem from those belonging to the main chicken categories marketed in Italy (N=5 flocks/market category): L farmed under either conventional systems (LC, FG slaughtered at 32-35 d) or free-range (LF, FG slaughtered at 56d) systems, M farmed under conventional systems (MC, FG slaughtered at 35-42d), H farmed under either conventional systems (HC, FG slaughtered at 45-50d) or organic (HO, FG slaughtered at 81d ). Samples were used to assess colour as well as protein and lipid oxidation by measuring carbonyls and TBARS, respectively. Data were analysed by One- way ANOVA considering the market category as main effect. When significant, means were separated by Tukey-HSD test (p<0.05). Overall, the market category significantly affected the colour parameters and oxidation level of both breast and thigh meat. Indeed, the higher (p<0.001) lightness (L*) observed in HO may likely be ascribed to the different maturity of breast meat and to the eventual development of muscular abnormalities affecting the phenomenon of light scattering. In addition, if compared to those obtained from other market categories, breasts and thighs belonging to LR exhibited the most noticeable differences in colour parameters. This finding may be ascribed to the different foraging behaviour (MG vs. FG) and pasture consumption of chickens with access to outdoor area. In addition, the remarkably higher (p<0.001) redness observed in both breast and thigh meat belonging to LC group may partly account for its higher (p<0.001) TBARS and carbonyls content. In fact, the pro-oxidant effect of heme group (which is, in its turn associated to higher a* values) may have favoured the development of oxidative reactions affecting both the protein and the lipid fractions. Overall, the findings obtained in the present study highlight the peculiar predisposition to undergo lipid and protein oxidation of breast and thigh meat obtained from chickens belonging to the different market categories available in Italy that should be carefully considered especially when raw meats are used for further processing.