Abstract
Sustainable incentives foster the use of plant-based ingredients as emulsifiers, but their functionality, for instance in terms of solubility, is far from optimal. The underlying reasons encompass a lack of characterization of the physicochemical properties of such ingredients. Thus, we comprehensively analyzed the composition of pea and lupin protein isolates and concentrates and highlighted a large part of non-proteinaceous compounds, notably lipids, constituting 3.8 to 11.7 wt.% (d.m.) of the powders. Over half of these lipids were phospholipids, which may have a pivotal impact regarding interfacial properties. A high-pressure homogenization (HPH) treatment was applied to aqueous suspensions of the ingredients. It broke down undispersed powder grains, enhanced protein solubility and released endogenous submicron lipid structures [1]. The interplay between these endogenous lipids and proteins was investigated regarding emulsifying and interfacial properties. Oil-in-water emulsions (10 wt.% oil) were prepared using HPH to reach droplet diameters around 2.5 µm. Protein surface load, composition measurements, and microscopic investigations suggested the formation of different interfacial films and an inner competition between proteins and phospholipids for interfacial adsorption. Therefore, we conducted complementary dilatational interfacial rheology analyses, using our commercial pea isolate on the one hand, and purified pea proteins and lipids on the other hand. Oscillatory deformations of the oil-water interface were analyzed by Lissajous plots (Figure 1), which substantiated the interactions between proteins and lipids by deciphering their respective contributions. The formation of mixed interfacial films according to the protein-to-lipid ratio was demonstrated, with notably a prevalent influence of pea lipids on the rheological signature of the mixed films. Atomic force microscopy confirmed the formation of mixed interfacial films where lipid domains coexisted with protein aggregates. These insights are key to understand the interactions between plant proteins and endogenous lipids in emulsions, and thereby to facilitate food products’ rational formulation with such complex ingredients