Effect of agitation and added cholesterol esterase on bioaccessibility of phytosterols in a standardized in vitro digestion model

Abstract

There is great interest in reaching a consensus method for in vitro digestion of foods. The COST INFOGEST network of researchers has developed a standardized protocol, which is appropriate for basic digestibility studies, but may be insufficient for more complex studies, such as micronutrient bioaccessibility. In the present study, the bioaccessibility of phytosterols (PS) was evaluated using the standardized and modified versions of the in vitro digestion protocol. The INFOGEST protocol was used without modification for 2% solutions of either free phytosterols (FPS) or esterified phytosterols (EPS) in soybean oil. The effect of two variables which have yet to be explored using the INFOGEST protocol was subsequently evaluated. Those variables are: (1) changing the mode of agitation from orbital shaking to head over heels (HOH) rotation and (2) adding pancreatic cholesterol esterase (CE) during the intestinal phase. Bioaccessibility of FPS was greater than that of EPS, and HOH rotation caused a further increase in bioaccessibility of FPS but not EPS. Addition of CE caused a slight, but significant improvement in bioaccessibility of EPS, though hydrolysis was incomplete. Our findings highlight a need for further evaluation of the standardized in vitro digestion protocol, especially for complex studies such as lipid bioaccessibility.