Structural Modulation and Application of High Internal Phase Emulsions Containing Proso Millet Bran Protein as a Delivery Carrier

In this study, a high internal phase emulsion (HIPE) stabilized by proso millet bran protein (PMBP) was developed to enhance the delivery of β-carotene. Specifically, the effects of PMBP concentration (2%, 4% and 6%) and aqueous phase pH (5, 7 and 9) on the structure and stability of HIPE were systematically evaluated. As the PMBP concentration or pH increased, the droplet size decreased and the absolute value of the zeta potential increased, indicating improved stability under refrigeration, freezing, and heating conditions. Furthermore, PMBP-stabilized HIPE significantly inhibited the release of free fatty acids and increased the in vitro bio-accessibility of β-carotene to 67.47%. This enhancement was mainly attributed to the dense interfacial adsorption layer formed by PMBP at the oil-water interface, which in turn strengthened both electrostatic repulsion and steric hindrance, thus slowing down lipid hydrolysis and protecting the encapsulated compounds. Overall, PMBP-stabilized HIPE shows strong potential for application in the delivery of lipophilic nutrients, providing a theoretical basis for its application in nutrient delivery systems and lipid alternatives.