An Electrochemical Study of the Effect of Temperature on the Adsorption Behavior of β-Lactoglobulin

Abstract

The surface adsorption behavior of the whey protein β-lactoglobulin A has been investigated at the platinum electrode using cyclic voltammetry. Plateau values of surface charge density were obtained for increasing concentrations of protein in the bulk solution. At temperatures ranging from 273 to 343 K, the surface charge density for protein adsorption increased due to the unfolding of the β-lactoglobulin molecule. At the higher temperatures of 348 to 368 K where denaturation of the protein occurs, the surface charge density was found to diminish, probably resulting from agglomeration of the protein, as indicated by the diminished percent of free sulfhydryl which was measured spectroscopically. The surface charge density was attributed to a flattening or denaturing of the protein at the electrode surface to allow adsorption of carboxyl groups accompanied by electron transfer at these anodic potentials. At 343 K, a threefold increase in surface adsorption was measured which would be indicative of several layers of denatured protein on the electrode surface. The surface charge density was very sensitive to pH and was found to decrease with increasing pH, which was consistent with results obtained by others.