Enhancing Bioaccessibility of Phytosterols Using Nanoporous Starch Aerogels and Supercritical Carbon Dioxide

Abstract

Food industry has recently prioritized the incorporation of bioactive compounds (e.g., phytosterols, tocopherols, carotenoids) into foods to design functional food products for improved health. Particularly, phytosterols have received great attention due to their health benefits such as LDL-cholesterol lowering effect, anticancer and anti-inflammatory properties. However, the bioavailability of phytosterols is very low owing to poor water solubility and high-melting-point crystalline structure which also severely limit the potential food applications of phytosterols. Therefore, the goal of this research was to form low-crystallinity phytosterol nanoparticles (PS-NSA) by impregnating phytosterols into nanoporous starch aerogels (NSAs) using a green method based on supercritical carbon dioxide (SC-CO₂) in order to enhance phytosterols’ bioavailability.

This research consisted of optimizing NSA production conditions for the highest surface area, investigating the in vitro digestibility of NSAs, generating PS-NSA by SC-CO₂ impregnation into NSA and optimizing the impregnation conditions, determining the water solubility, release and bioaccessibility of PS-NSA, and evaluating the bioaccessibility of the PS-NSA in food applications. At the optimized production conditions, SC-CO₂ drying generated NSAs with unique properties (surface area of 60 m2/g, pore size of 20 nm, pore volume of 0.27 cm³/g, density of 0.12 g/cm³, and porosity of 92%) and overcame the shrinking problem of the air drying by eliminating the surface tension and capillary forces during drying. A study on the digestibility of NSA was conducted where NSA formation resulted in a promising increase in the resistant starch (RS) content. SC-CO₂ impregnation into NSA generated spherical phytosterol nanoparticles (70 nm) wherein the NSA played a critical role in preventing the formation of large phytosterol crystals. The crystallinity of phytosterols was decreased with impregnation into NSA which improved the water solubility of phytosterols (37-fold). PS-NSA also showed enhanced solubilization in both simulated gastric and intestinal fluids. Furthermore, a study on the optimization of the SC-CO ₂ impregnation conditions revealed that more isolated PS-NSA were produced at higher cooling rates. The bioaccessibility of phytosterols increased by 20-fold with the formation of PS-NSA. Lastly, the performance of PS-NSA in granola bar and pudding formulations was investigated, herein enhanced bioaccessibilities were achieved even with low- and non-fat food formulations.