Prolonged 20 h heating of chicken meat in water at 75°C softens the meat, increases the levels of endogenous and degraded metabolites in the stock, but depletes reduced glutathione and glutamine

We investigated the effects of 20 h of heating at 60°C and 75°C, after initial 20 min of heating at 85°C, on the texture of chicken meat and on the chemical components of chicken stock. Prolonged heating at both temperatures decreased the toughness of chicken meat, especially of the skin. Totally, 130 of the 195 metabolites detected using untargeted metabolomics increased > 50% after prolonged heating with overall shifts of chemical component profiles smaller at 60°C. At 75°C, the levels of 16 metabolites (including creatinine, indoxyl-sulfate, and cysteine-S-sulfate associated with elevated health risks) increased > 8-fold; and 4 metabolites (including glutamine and reduced glutathione, one of the main cellular antioxidants) decreased > 8-fold. Reduced glutathione was relatively abundant in the initial stock and was still detected at 60°C, but not at 75°C. Our results support cooking at a lower temperature and provide a molecular basis for improving chicken recipes.