Stabilities of bovine β-lactoglobulin/retinol or retinoic acid complexes against tryptic hydrolysis, heating and light-induced oxidation

Abstract

Complexes of β-lactoglobulin and retinol or retinoic acid were subjected to tryptic hydrolysis. Susceptibilities of β-lactoglobulin/retinol and β-lactoglobulin/retinoic acid complexes to tryptic hydrolysis were significantly lower than that of free β-lactoglobulin. The Stokes radii of β-lactoglobulin/retinol (2.2 nm) and β-lactoglobulin/retinoic acid (2.3 nm) estimated by gel filtration chromatography were relatively smaller than that of β-lactoglobulin (2.57 nm). Heat stabilities of β-lactoglobulin/retinol and β-lactoglobulin/retinoic acid complexes increased significantly on heating at 60 °C for 10 min. β-Lactoglobulin/retinoic acid complex was more heat stable than β-lactoglobulin/retinol. Retinol and retinoic acid bound to β-lactoglobulin were less susceptible to light-induced oxidation by UV-light irradiation than those which were free or bound to bovine serum albumin. © 1996 Academic Press Limited.