Soy Protein Isolate–Maltodextrin–Pectin Microcapsules of Himalayan Walnut Oil: Complex Coacervation under Variable pH Systems and Characterization

The basic aim of this study was to encapsulate Himalayan walnut oil (HWO) in different concentrations of soy protein isolate (SPI), maltodextrin (MD), and pectin at varying pH (4.0 and 7.0) by complex coacervation. The formation of primary and secondary oxidation products showed a 6–8-fold increase in free oil (0.8–60 meq O2/kg, 1–88) compared to encapsulated HWO (1–40 meq O2/kg, 1–34) for a storage period of 60 days. The coacervates developed between SPI–MD–pectin at pH 4.0 exhibited favorable physicochemical properties like an optimum moisture content, aw, color, and density with maximum retention of omega fatty acids (69%). The antioxidant potential assessed by 2,2′-diphenyl-1-picrylhydrazyl (DPPH*) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS*) and the metal chelating ability (MCA) showed that coacervates prepared at pH 4.0 depicted a lower DPPH [142%] and a higher ABTS [39%] and MCA [41%] than those at pH 7.0 (DPPH [144%], ABTS [34%], and MCA [38%]). An in vitro digestion model showed increased antioxidative properties after gastric digestion compared to intestinal digestion. The amount of free fatty acids released from gastric digested emulsions during gastrointestinal digestion was 1400 mg/g with maximum omega fatty acid retention. The model indicated good lipid digestion and absorption of lipophilic bioactives in the small intestines.