Interfacial adsorption of peptides in oil-in-water emulsions costabilized by Tween 20 and antioxidative potato peptides.

Previous studies have shown that soybean oil-in-water (O/W) emulsions prepared with potato protein hydrolysate (PPH) are remarkably stable against oxidative changes. It was hypothesized that partitioning of peptides at the emulsion interface plays an important role in this phenomenon. The present study was conducted to examine the structural characteristics of the interfacial membrane. As revealed by atomic force microscopy, oil droplets costabilized with PPH and Tween 20 were more uniform than those stabilized with Tween 20 only (control). Confocal laser scanning microscopy images indicated the existence of peptides directly anchored into the interfacial membrane. The adsorbed peptides were mostly short oligopeptides composed of two to seven amino acids, of which Ser-Phe-Asp-Leu(Ile)-Lys matched the sequence of patatin. The adsorption of these peptides appeared to both improve the integrity of the interface and contribute to the oxidative stability of the emulsions. Furthermore, cryogenic transmission electron microscopy illustrated the morphology of the interfacial membrane as a noncontinuous short fibril structure. Partitioning of antioxidative peptides in the interfacial membrane provided steric hindrances and electrostatic effects to inhibit oxidation.