Plant-based flaxseed oil microcapsules fabricated from coacervation of gluten at oil droplet surface: Microstructure, oxidation stability, and oil digestion control.

Abstract

This study aimed to develop microcapsules with wheat gluten-coated oil droplets to enhance the oxidation stability and control the digestibility of flaxseed oil. The microcapsules were fabricated using a three-step procedure: (i) flaxseed oil was homogenized with an alkaline gluten solution to form oil-in-water emulsions containing small gluten-coated oil droplets (320-400 nm); (ii) the pH of these emulsions was then neutralized to facilitate the deposition of gluten around the oil droplets, thereby forming a thick layer; (iii) a flaxseed oil microcapsule powder was then prepared by spray drying. During the microcapsule formation, intermolecular interactions, including hydrophobic interactions and hydrogen bonds, were involved in the coacervation of gluten at the emulsion surface. The resultant microcapsules with a multiple-core structure had external diameters of 4-26 µm and encapsulation efficiencies of 90%-94%. The microencapsulated oil powders contained a relatively high flaxseed oil content (60%-80%). Among them, the sample with 60% oil content demonstrated the best stability in resisting oil droplet coalescence; thus, it exhibited a higher lipolysis rate and extent during simulated gastrointestinal digestion. A 30-day accelerated storage study showed that encapsulation of the flaxseed oil improved its resistance to oxidation. These findings suggest that the pH-deposition method can successfully produce microencapsulated polyunsaturated lipids using all plant-derived ingredients, which may facilitate their use in new plant-based foods through a green and sustainable approach.