Sodium caseinate/flaxseed gum interactions at oil–water interface: Effect on protein adsorption and functions in oil-in-water emulsion

Abstract

Effects of flaxseed gum (FG) on the adsorption of sodium caseinate (CN) at the oil–water interface and the stability of the oil-in-water emulsions stabilized by CN were studied. Both FG concentration and pH showed significant effects on biopolymer interactions, and pH 5.5 was a critical value for FG/CN interactions. Measurements of dynamic interfacial pressure were performed as a function of FG concentration ranging from 0 to 0.3 wt%. Interfacial pressure of the CN/FG solution at the oil–water interface reached the highest when the FG concentration was 0.1 wt%. The diffusion rate (kdiff) of CN to the interface increased with rising FG concentration, whilst the rates of penetration (kP) and rearrangement (kR) of CN at the interface decreased. The stability of emulsion was improved at 0.1 wt% of FG, but decreased at 0.2 and 0.3 wt% of FG due to depletion flocculation caused by the increase of unabsorbed FG. Confocal laser scanning microscopy revealed the pronounced effect of FG on the microstructure of emulsion. Surface protein concentration exhibited a decrease with increasing FG concentration although no significant difference (p < 0.05) was found in protein composition.