Enhancing the bioaccessibility of phytosterols using nanoporous corn and wheat starch bioaerogels

Abstract

Bioavailability of phytosterols is very low due to their crystalline structure and poor water solubility, limiting their potential health benefits. In this study, a novel approach to forming low crystallinity phytosterol nanoparticles was developed using nanoporous starch aerogels, namely wheat starch aerogels (WSAs) and corn starch aerogels (CSA), in combination with supercritical carbon dioxide (SC-CO₂) to improve the bioaccessibility and in turn bioavailability of phytosterols. Starch aerogels with outstanding properties (WSA with a surface area of 62 m2/g and pore size of 19 nm; CSA with a surface area of 221 m²/g and pore size of 7 nm) were used as a mold to form phytosterol nanoparticles. The highest phytosterol impregnation capacity was obtained with CSA monolith (195 mg phytosterols/g CSA). Impregnation into powder or monolithic forms of the aerogels resulted in different phytosterol morphology where the monolithic form prevented formation of large plate-like phytosterol crystals. Impregnation into WSA monolith (WSA-M) generated low crystallinity phytosterol nanoparticles (70 nm). Bioaccessibility of the phytosterols increased by 20-fold when impregnated into WSA-M. The hydrolysis of CSA (30-39%) was lower than that of WSA (55-59%) during simulated digestion, which negatively affected the release of phytosterols.

Practical applications: Practical applications include: (i) a novel process that can decrease the size and crystallinity of phytosterols and thus improve their bioavailability; (ii) a blueprint to apply to other water insoluble food bioactives; and (iii) the transfer of green technology to food manufacturers. Longer-term, this novel approach will (i) improve the health benefits of water-insoluble bioactives; (ii) enable food manufacturers to add water-insoluble bioactives into low- and high-fat foods to produce health-promoting foods; (iii) improve public health through diet; (iv) enhance the cost-benefit ratio of water insoluble bioactives; (v) avert toxic chemicals & environmental pollution; and (vi) lower the costs of handling, storage & transportation of bioactives.

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