Unravelling the impact of emulsifier blends on interfacial properties and in vitro small intestinal lipolysis of oil-in-water emulsions

Blends of emulsifiers are used more often to modulate the functionality of oil-in-water (O/W) emulsions such as lipolysis kinetics. However, the rational design of such emulsifier blends is often not well understood. The present research aimed to gain in-depth understanding into the effect of a combination of emulsifiers on lipid digestion kinetics. For this purpose, the interfacial tension (IFT), microstructure during digestion, and in vitro lipid digestion kinetics were monitored. Three emulsifiers, lysolecithin (LL), monoolein (MG), and glyceryl polyethyleneglycol ricinoleate (SYN), were evaluated individually, in pairs at a 1:1 ratio, in pairs at a commercially common ratio, and all three together in a commercially relevant ratio (LEX). Significant differences were seen between all parameters evaluated across various emulsions. SYN and LL substantially reduced the interfacial tension and produced emulsions with small droplet sizes (0.63–1.50 μm) throughout digestion and comparatively higher rates (7.02 and 5.43 min−1, respectively) and extents of lipolysis (68.42 and 58.60%, respectively), while the opposite occurred for MG (0.66–9.93 μm; 2.32 min−1 and 37.98%). Nevertheless, when MG was combined with sufficient quantities of SYN or LL, digestion kinetics substantially increased. Furthermore, our findings demonstrated that the lipolysis kinetics of LEX were mainly driven by SYN and LL, which are hypothesized to mainly reside at the interface based on their ability to reduce IFT. Therefore, the present research demonstrated again that lipolysis kinetics are strongly driven by the interfacial composition of O/W emulsions. Such insights allow further optimization and design of emulsifier blends to modulate digestion kinetics.