Carotenoid bioaccessibility and the relation to lipid digestion: A kinetic study

The micellar incorporation of carotenoids (lycopene, α- and β-carotene) and lipid digestion products (free fatty acids, FFAs, and monoacylglycerides, MAGs) during in vitro digestion of oil-in-water emulsions was investigated by a kinetic approach. A fractional conversion model could adequately describe the hydrolysis of triacylglycerides, formation of FFAs and MAGs, and micellar incorporation of carotenoids, FFAs and MAGs. The release of FFAs and MAGs from TAGs proceeded faster than their incorporation into micelles. Rate constants of carotenoid micellar incorporation were inversely proportional to their hydrophobicity and dependent on the isomeric configuration, being the incorporation of the cis faster than their all-trans isomers. Furthermore, a positive linear relation was found between the micellar incorporation of carotenoids and lipid digestion products. The isomeric form of carotenoids did not affect such relation. The present kinetic approach can be useful to gain mechanistic insight into carotenoid bioaccessibility as affected by various process- and product-related factors.