Effects of Palm Stearin and Palm Olein Emulsion Crystallinity on Beta-carotene Degradation and in vitro Bioaccessibility

Abstract

The encapsulation of lipophilic vitamins and other bioactive molecules in nanoemulsions can promote their stabilization, bioaccessibility, and bioavailability, which impacts various physiological processes. This research investigated how triacylglycerol crystallinity influenced the effect of beta-carotene (BC) encapsulation on emulsion properties, the degradation of BC nanoemulsions over time, and BC bioaccessibility during static in vitro digestion. Emulsions composed of 10 wt% palm stearin (PS) or palm olein (PO), 0.4 wt% Span 60, and 0.01 wt% BC were tempered to achieve four emulsions with different physical states: crystalline solid (PS-SE-BC); partially crystalline solid (PS-SE-25-BC); undercooled liquid (PS-LE-BC); and a control emulsion (PO-BC) not susceptible to crystallization. BC degradation under accelerated lighting conditions at 37o C, melting behaviour, and particle size were measured at baseline and after 14 days. Emulsions were subjected to simulated in vitro gastric and duodenal digestion for up to 24 hours, and BC bioaccessibility was determined at 1, 2, 4 and 24 hours. The baseline particle size distributions for all emulsions at baseline were similarly monomodal, centred around 0.8 um, and unchanged from emulsions without BC. However, at day 14, all the palm stearin emulsions had monomodal distributions but consisted of larger particles. The melting behaviour of emulsions at baseline and day 14 were similar, except for PS-LE-BC, which contained some solid fat by day 14. All emulsions showed statistically similar BC degradation after 14 days (P >0.05), and BC bioaccessibility was similar between all emulsions (P >0.05). Therefore, the presence of lipid crystallinity in the nanoemulsions did not significantly influence BC degradation or BC bioaccessibility. These results help to explain how lipid crystallinity may impact bioactive stability and bioaccessibility, highlighting its wide-ranging implications for nutrient delivery.