Emulsion design for the delivery of beta-carotene in complex food systems

beta-Carotene has been widely investigated both in the industry and academia, due to its unique bioactive attributes as an antioxidant and pro-vitamin A. Many attempts were made to design delivery systems for beta-carotene to improve its dispersant state and chemical stability, and finally to enhance the functionality. Different types of oil-in-water emulsions were proved to be effective delivery systems for lipophilic bioactive ingredients, and intensive studies were performed on beta-carotene emulsions in the last decade. Emulsions are thermodynamically unstable, and emulsions with intact structures are preferable in delivering beta-carotene during processing and storage. beta-Carotene in emulsions with smaller particle size has poor stability, and protein-type emulsifiers and additional antioxidants are effective in protecting beta-crotene from degradation. Recent development in the design of protein-polyphenol conjugates has provided a novel approach to improve the stability of beta-carotene emulsions. When beta-carotene is consumed, its bioaccessibility is highly influenced by the digestion of lipids, and beta-carotene in smaller oil droplets containing long-chain fatty acids has a higher bioaccessibility. In order to better deliver beta-carotene in complex food products, some novel emulsions with tailor-made structures have been developed, e.g., multilayer emulsions, solid lipid particles, Pickering emulsions. This review summarizes the updated understanding of emulsion-based delivery systems for beta-carotene, and how emulsions can be better designed to fulfill the benefits of beta-carotene in functional foods.