Inhibition of pancreatic lipase by ovalbumin and β-lactoglobulin A at the air/water interface

Abstract

The kinetics of ovalbumin and β-lactoglobulin A adsorption at the air/water interface were studied in the abence or presence of 1,2-didecanoylglycerol (dicaprin) monolayer. The lipolytic inhibition capacities of ovalbumin and β-lactoglobulin A are explained in terms of their adsorption kinetic properties. The adsorption of the proteins can be controlled by a diffusion and/or an adsorption energy barrier step. Assuming the adsorption to be diffusion-controlled, the apparent diffusion coefficient ( D app was calculated and compared with the diffusion coefficient ( D) measured independently. When calculated, D app was found to be lower than D, which shows that an adsorption energy barrier exists. The energy barrier of β-lactoglobulin A was found to be lower than tat of ovalbumin. Assuming the adsorption energy barrier to be a rate-controlled process, the adsorption constant was calculated. β-Lactoglobulin A has a higher adsorption rate. The surface rheological dilatational properties during adsorption of the proteins and enzymes were also studied. In the presence of β-lactoglobulin A, the previously elastic properties of the lipid monolayer became viscoelastic. A mixed monolayer of ovalbumin/dicaprin or β-lactoglobulin A/dicaprin was spread and used to study the inhibition of horse pancreatic lipase activity at the air/water interface. A critical lipid/protein ratio was found to exist, above which enzymatic hydrolysis of dicaprin was observed. This molar ratio is 1 in the case of a mixed ovalbumin/dicaprin monolayer and 9 in the case of a mixed β-lactoglobulin A/dicaprin monolayer.