Production system and muscle type affect the formation of oxidation products during in vitro gastrointestinal digestion of chicken meat

Chicken meat is recognized as highly sensitive to oxidative reactions due to the high unsaturation of muscle lipids. Oxidative reactions during heating and gastrointestinal digestion of chicken meat lead to the formation of various lipid- and protein oxidation products. It was hypothesized that differences in production system (conventional vs. organic) and muscle type (breast vs. thigh) may influence the formation of lipid oxidation products (LOPs), including 4-hydroxy-2-nonenal, hexanal, propanal, and thiobarbituric acid reactive substances, as well as protein oxidation (protein carbonyl compounds, PCCs) during in vitro gastrointestinal digestion of chicken meat. To test this hypothesis, chicken meat from two distinct broiler production systems was used, i.e. conventional intensive and organic farming. From five farms per production system in Belgium, 10 chickens (mixed sex, two per farm) were sampled, and distributed in four groups: conventional breast, conventional thigh, organic breast, and organic thigh (n=10 per group). Prior to the in vitro digestion, 100g thigh and breast meat (skinless) was minced and heated until the core temperature reached 70°C. Heme iron (heme-Fe), polyunsaturated fatty acids (PUFAs), and antioxidants (α-tocopherol, carnosine, anserine) were measured in heated meats. The static in vitro model simulated digestion in the mouth, stomach, and small intestine at 37°C. The LOPs and PCCs were analyzed in heated meats and digests. Data were analyzed using two-way ANOVA. In general, meats from the organic production system and thigh muscle contained significantly higher heme-Fe and PUFAs, which contributed to increased levels of LOPs in meats and their digests following in vitro digestion. Specifically, organic thigh meat contained the highest levels of heme-Fe (+134%) and PUFAs (+148%) compared to the mean values of the other three groups, which was accompanied by a 3.5 to 18-fold increase in LOPs levels following heating and a 1.6 to 4.4-fold increase after digestion. Additionally, thigh meat displayed greater PCC levels in heated samples (+44%) and digests (+25%) compared to breast meat, irrespective of the production system. This highlights the role of production system and muscle type in chicken meat oxidation during in vitro digestion, urging further in vivo studies on the biological implications of these oxidation products