Effect of divalent cations on bovine serum albumin (BSA) and tannic acid interaction and its influence on turbidity and in vitro protein digestibility.

Tannins, proteins, and divalent cations interactions are important for many processes in the food industry and human and animal nutrition and health. The effect of magnesium, calcium, and manganese on the interaction, turbidity, and in vitro protein digestibility of bovine serum albumin and tannic acid complexes was studied. The divalent cations increase the affinity and influence the enthalpy and entropy changes of the protein and tannin binding. Magnesium maintained the nature of interactions, and calcium and manganese changed the binding mechanism. The factor that most influenced turbidity was the tannic acid and divalent cations binary interaction. Samples containing tannic acid and magnesium and calcium decreased the protein digestibility. Manganese increased the in vitro protein digestibility when compared with samples without salt addition; nevertheless, the complexes formed was higher. These finds can help in the understanding of interactions involved food system and in physiological conditions.