Effect of pectin adsorption on the hydrophobic binding sites of β-lactoglobulin in solution and in emulsion systems

Abstract

The impact of high methoxyl pectin adsorption on β-lactoglobulin (βLG) conformation in solution and at the interface of an oil-in-water emulsion was investigated using 6-propionyl-2-(dimethylamino)naphthalene and retinol probes to monitor βLG binding availability for hydrophobic compounds. The effects of pH (2.0–9.0) and ionic strength of NaCl (0–330 mm) and CaCl2 (0–1 m) were also examined. An increase in surface hydrophobicity (S0) and retinol binding was observed for pH above 7 where the protein had a more flexible and open conformation. Pectin attachment to βLG at pH 4 had a significant impact on S0 due to protein unfolding, confirmed by differential scanning calorimetry. Retinol binding was not affected in the closed calyx structure of βLG. Similar behaviour occurred for multilayer emulsions. The addition of salts caused a reduction in S0 and retinol binding as the protein underwent partial aggregation in solution and at the interface of the primary emulsion.