In vitro digestibility kinetics of oil-in-water emulsions structured by water-soluble pectin-protein mixtures from vegetable purées

Abstract

The potential use of water-soluble biopolymers from vegetable-origin in structuring oil-in-water emulsions and the influence on their digestion was investigated. The aqueous/serum phase, containing water-soluble biopolymers, of processed carrot and broccoli purées were isolated, lyophilized and then used either as the emulsifier or component in the continuous phase of carotenoid-loaded o/w emulsions. The kinetics of lipid digestion, micelle formation and carotenoid bioaccessibility of such emulsions were monitored during the in vitro small intestinal phase.The vegetable sera were characterized by a mixture of pectin and protein, in which free proteins and/or proteins-linked to pectin were probably present. Such pectin-protein mixtures exhibited an emulsion stabilizing capacity that determined the rate and extent of lipolysis, micelle formation, and carotenoid bioaccessibility. Emulsion destabilization during the gastric phase caused larger droplets in the emulsion formulated with broccoli serum containing high protein content and low Mw pectin compared to carrot serum with low protein content and high Mw pectin. In turn, a broccoli serum-emulsion presented slower rate and lower extent of lipolysis, micelle formation and consequently carotenoid bioaccessibility. By contrast, broccoli serum as a component in the continuous phase had no effect on lipolysis, micelle formation and carotenoid bioaccessibility, while, carrot serum limited the extent of carotenoid bioaccessibility without affecting the lipolysis and micelle formation. Carrot serum in the continuous phase hindered the transfer of carotenoids into mixed micelles. Water-soluble vegetable-based biopolymers (which can be tuned by processing) can be potentially used as natural emulsifiers that might modulate lipolysis and bioaccessibility of lipophilic bioactive compounds.