Enhanced water dispersibility and permeability through a Caco-2 cell monolayer of β-cryptoxanthin extracted from kumquats by complexation with casein

[Display omitted] •A complex between β-Cryptoxanthin (BCX) and casein (Cas) was prepared.•The complexation significantly improved the apparent solubility of BCX.•The quantity of BCX permeated through a Caco-2 cell monolayer was enhanced.•Complexation of BCX with Cas improved dramatically the bioavailability of BCX. β-Cryptoxanthin (BCX) possesses potential therapeutic and health benefits. However, BCX absorption is low because of its poor aqueous solubility. In this study, a complex between BCX and casein (Cas) was prepared to improve the water dispersibility and bioavailability of BCX. BCX was recovered quantitatively from freeze-dried kumquat powder through solid–liquid extraction and saponification. The complexation significantly improved the apparent solubility of BCX under acidic and neutral conditions. A cell membrane permeation test using a Caco-2 cell monolayer was performed to evaluate the bioavailability of the BCX–Cas complex. This complex and a blank sample were digested in vitro and added to the apical side of the Caco-2 cell membrane. The quantity of BCX that permeated using the BCX–Cas complex after 24 h was 22.7 times greater than that of the blank. Thus, complexation of BCX with Cas improved dramatically the bioavailability of BCX from a kumquat extract.