EFFECT OF THERMAL-DENATURATION ON VANILLIN BINDING TO SOME FOOD PROTEINS

Interactions of food proteins - beta-lactoglobulin (BLG). bovine serum albumin (BSA) und ovalbumin (OA)- with vanillin and effect of thermal denaturation of the proteins on vanillin binding were studies by US-V IS spectrophotometry. This method has its origin in characteristic cha nges in the vanillin absorption spectrum at vanillin-protein complex f ormation and allows to calculate concentrations of the bound and free ligand in aqueous solutions. Thermodynamic parameters, the intrinsic a ssociation constants and the number of binding sites of the vanillin b inding to the native and thermodenaturated proteins (monomers and clus ters) were determined. It is shown that the vanillin affinity for the native proteins is decreased in the following order: BSA > BLG > OA. T his sequence is reversed for the protein thermoclusters. The stepwise annealing allowing to derive complex protein mixtures composed of diff erent types of the native and denatured protein mixtures composed of d ifferent types of the native and denatured protein particles was appli ed to thermodenaturation of BSA. The vanillin affinity for BSA is decr eased in the order: native protein > denaturated monomer > denaturated clusters. Vanillin interaction with the proteins is mainly electrosta tic in nature.