EFFECTS OF PHYSICOCHEMICAL PARAMETERS OF A MODEL WINE ON THE BINDING OF GAMMA-DECALACTONE ON BOVINE SERUM-ALBUMIN

To understand the effect of temperature, pH and the composition of alcoholic beverages in flavour-protein interactions, the binding of gamma-decalactone to bovine serum albumin (BSA) was investigated using the equilibrium dialysis method. Thermodynamic analysis revealed that the affinity of aroma compound for BSA is higher at 10 degrees C than at 20 and 30 degrees C, while the number of binding sites (n = 6-7) is not modified at the three temperatures. pH did not have any appreciable effect on flavour binding in the presence of ethanol, but it was observed that a decrease of 1.8 pH unit reduces binding by 40% in its absence. The presence of ethanol has no effect on the number of binding sites and on the standard free energy (Delta G degrees) of the interactions. On the other hand, the binding constant (k) was 4.8-fold higher in water than in model wine (pH 3.5, ionized compounds, 10% w/w ethanol); so, the affinity of volatile compound was clearly lower in the model wine than in water.