Effect of extraction pH and post-extraction heat treatment on the composition and interfacial properties of peanut oil bodies

Abstract

Oil bodies (OBs) are composed of internal triglyceride and external phospholipids with embedded surface proteins. The phospholipids and surface proteins not only play an important role in the stability of the natural OB droplets, but also endow emulsifying property of OBs, as they can participate in the emulsification process of a formula. In order to investigate the effects of extraction pH and post heat treatment on the interfacial properties of OBs, the interfacial composition and structure of peanut OBs extracted at different pHs, and heat treated at 30 ℃, 60 ℃, 90 ℃ after extracted at pH 7.5 were characterized, and their interfacial adsorption kinetics, interfacial isothermal curve, and viscoelasticity were studied using dilatational rheology and Langmuir-Blodgett (LB) film analyzer. The results showed that the content of peanut OBs surface proteins decreased with the increasing of extraction pH and heat treatment temperature. The particle size of peanut OBs extracted at pH 7.5 was the smallest and the surface hydrophobicity of these OBs heated at 30 ℃ was the highest, which resulted in their fastest increase of interfacial pressure and strongest viscoelasticity of the absorbed interfacial film at the oil-water interface. The peanut OBs extracted at different pH and heat-treatment demonstrated diffusion, adsorption and rupture/structural rearrangement at the air-water interface as time went on according to the interfacial compression isotherm curve, which are correlated with their interfacial dilatational rheology behaviors and emulsification ability. These findings provide a reference for the future utilization of peanut OBs as emulsifiers in the food and cosmetic industries.