Interfacial and oil-in-water emulsifying properties of ovalbumin enriched in amyloid-like fibrils and peptides

Abstract

The combination of heat and enzymatic treatment on ovalbumin (OVA) has been shown to lead to a mixture of amyloid-like fibrils (ALFs) and peptides. Due to their gelling behavior, these mixtures are able to stabilize oil-in-water (O/W) emulsions. As peptides present alongside the OVA ALFs can impact interfacial behavior, it is necessary to remove them. Here, the ability to separate peptides from OVA ALFs by ultracentrifugation and dialysis was investigated. Size exclusion-high performance liquid chromatography results showed that dialysis produced pure OVA ALFs, while ultracentrifugation resulted in both a fibril- and a peptide-enriched fraction. Drop shape tensiometry confirmed that dialysis removed peptides, as a delayed decrease in interfacial tension indicated slower adsorption kinetics of larger structures. This was further supported by an increase in dilatational elasticity compared to samples containing peptides. Emulsions [10.0 % (O/W)] with only fibrils (obtained by dialysis) contained oil droplets that were noticeably larger than those in emulsions containing peptides. However, these emulsions exhibited high creaming and coalescence stability. In contrast, emulsions with peptide-enriched OVA dispersions contained smaller oil droplets but were prone to coalescence due to the lack of a thick viscoelastic layer or a highly viscous continuous phase. The obtained results suggest that peptides, when present, preferentially adsorb at the interface, favoring small emulsion droplets, while the long OVA ALFs form a gel-like network in the continuous phase. This distinct interfacial behavior of peptides and ALFs, in the presence or absence of each other, may be useful when considering their use in food products.