Chemical equilibrium of minced turkey meat in organic acid solutions

The distribution of acid (HA), anions (A−), free protons (H3O+) and bound protons (Hb), in homogenized turkey meat was evaluated at various meat/water mass ratios of (1/4-1/10) during titration with acetic acid (0.25 N) or lactic acid (0.2 N). Hb concentration was determined by titration with hydrochloric acid (0.075 N) and a correlation for [Hb] = f(pH) was proposed. A procedure was used to calculate the fractions of the various species in equilibrium, starting from an initial acid concentration in a meat/water system and assuming the accuracy of the pKa value of the pure weak acids despite the chemical complexity of meat. Calculated results were in very good agreement (±0.15) with experimental pH values, whatever the acid, meat batch or meat/water mass ratios used. Less than 1% of the total protons were free (H3O+) and determined the meat pH.