Absorption mechanism of whey-protein-delivered curcumin using Caco-2 cell monolayers

• β-Lg–CCM complex and nanoemulsion improved the absorption rate of CCM.
• The CCM in the nanoemulsion may be absorbed by the digestion–absorption route.
• The hydrolysis of oil in nanoemulsion affected the absorption of CCM.
• Upon combining with β-Lg the water solubility and pH stability of CCM increased.
• Two different routes existed simultaneously in the absorption of CCM from complex.

Curcumin (CCM) is a bioactive polyphenolic compound that suffers a low bioavailability because of its low water solubility. In this work β-lactoglobulin (β-Lg) and nanoemulsion were used as carriers to deliver curcumin. The pH stability of β-Lg–CCM was investigated. The digestion of β-Lg–CCM and the nanoemulsion was studied using an in vitro gastrointestinal model. The effect of different carriers on the permeability of curcumin was assessed using the Caco-2 cell monolayer model. The results revealed that the water solubility and the pH stability of curcumin significantly increased by binding with β-Lg. In SDS–PAGE experiments the β-Lg–CCM complex and nanoemulsion were found to be resistant to pepsin digestion but sensitive to trypsin. In the permeability experiment it was shown that the digested nanoemulsion and β-Lg–CCM improved significantly the permeation rate of curcumin.