Enzymatic Hydrolysis of Milk Proteins Used for Emulsion Formation. 1. Kinetics of Protein Breakdown and Storage Stability of the Emulsions

Abstract

Hydrolysis of β-lactoglobulin and sodium caseinate in solution or while adsorbed at oil-water interfaces in emulsions formed from unmodified proteins was carried out with trypsin. The hydrolysis was monitored by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and dynamic light scattering. The stability during storage of the emulsions containing hydrolyzed proteins was also investigated by small-angle laser light scattering. The order of the hydrolysis of the individual caseins at the oil surface was β > αs >>> κ compared with αs > β > κ in solution. The overall rate of hydrolysis of sodium caseinate was the same whether adsorbed to the interface or in solution. Conversely, the rate of hydrolysis of β-lactoglobulin was much higher on the surface of emulsion than in solution. Emulsions formed from hydrolyzed protein solutions were less stable during storage than those formed from unmodified proteins and subsequently hydrolyzed or those formed with unmodified protein solutions. Keywords: Emulsions; casein; β-lactoglobulin; trypsin; peptides; emulsion stability