Perilla oil emulsions stabilized by casein-dextran sulfate nanocomplexes with and without curcumin

Protein-polysaccharide nanocomplexes are potential particulate emulsifiers to improve physical and chemical stability of emulsions containing polyunsaturated fatty acids. This study prepared nanocomplex dispersions with 2.0 % w/v sodium caseinate and 0–0.4 % w/v dextran sulfate (DS) with and without 0.1 % w/v curcumin. The dispersions exhibited a Z-average diameter of 124.61–182.46 nm, a polydispersity index of 0.37–0.52, and a zeta potential between −30.1 and −34.9 mV, with a curcumin encapsulation efficiency of higher than 75 %. These nanocomplexes were used to emulsify 60 % v/v perilla oil (PO) through shear homogenization and sonication. Emulsions showed discrete droplets in light and confocal laser scanning microscopy. The creaming index decreased as DS concentration increased, remaining below 6 % after 30 days of storage Emulsions had >70 % DS, >80 % caseinate, and 100 % curcumin adsorbed on the oil droplet surface. For oxidative stability at 55 °C for 15 days, emulsions prepared with 2.0 % w/v caseinate and 0.4 % w/v DS, with and without curcumin, showed a maximum of 40 % reduction in the peroxide value and 71 % reduction in the thiobarbituric reactive substances value from those of bulk PO. The present study showed the significance of casein-DS nanocomplexes for the physical and chemical stability of PO emulsions. [Display omitted] •Casein and dextran sulfate formed nanocomplexes with and without curcumin.•All dextran sulfate molecules formed nanocomplexes.•Nanocomplexes served as Pickering emulsifiers and stabilized emulsions.•Nanocomplexes improved the oxidative stability of perilla oil emulsions.•Interfacial casein in nanocomplexes was key in the oxidative stability of perilla oil.