Carotenoids are hydrophobic and their absorption depends upon efficient release from the food matrix and subsequent solubilization by bile acids and digestive enzymes, culminating in their incorporation into micelles (Figure 2). Carotenoids are disassociated from their native environment in the plant tissue during food processing and digestion (acidic conditions and enzymatic hydrolysis) in the stomach (Khachik and others 2002). Also, carotenoids must also be released from their native environment during mastication,where mechanical forces and saliva enzymes disrupt tissues and cellular compartments (Parada and Aguilera 2007). The main part of carotenoid metabolism occurs in the small intestine where
they must also be dissolved in dietary lipids before they can be absorbed. Dietary lipids have been considered to be an important factor for stimulation of bile flow into the intestine and micelle formation (Furr and Clark 1997; Roodenburg and others 2000).Lipids are capable of attaching to carotenoids due their hydrophobic character, but also may attach to water molecules that, in conjunction with bile salts, result in the formation of micelles and solubilized carotenoids in the system (Hof and others 2000). This allows carotenoids to be absorbed passively from the micellar phase trough the lumen of the intestine to the lymphatic and blood circulatory system. However, it is unknown if all the carotenoids present in a mixed micelle are absorbed, or whether some are left behind in association with unabsorbed bile salts and cholesterol to be absorbed more distally or lost to the large intestine where they can exert their antioxidant properties.