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

摘要

The impact of high methoxyl pectin adsorption on beta -lactoglobulin ( beta LG) 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 beta LG 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 beta LG 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 beta LG. 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.