Loading curcumin in shellac/sodium dodecyl sulfate composite nanocapsules with the pH-cycle method to improve acid stability and bioaccessibility

Shellac micelles are promising nano-systems for delivering curcumin but precipitate below pH 7. In the present study, sodium dodecyl sulfate (SDS) was combined with shellac to improve dispersion acid stability and cur-cumin bioaccessibility. Dispersions were prepared with 1.0 mg/mL curcumin, 25 mg/mL shellac, and 0-20 mg/ mL SDS at pH 7.0, 4.6, and 3.0. SDS improved the encapsulation efficiency (EE; up to 83.7 % vs. 75.8 %) at pH 7.0 and enabled the dispersion stability at pH 4.6 (61-70 % EE) and 3.0 (60-64 % EE). The Z-average diameter was similar at pH 7.0 (13-18 nm) but was smaller at a higher SDS concentration at pH 4.6 (50-108 nm) and 3.0 (46-91 nm). The bioaccessibility of curcumin in the 20 mg/mL SDS treatment was 32-33 % and > 65 % after simulated gastrointestinal and colonic digestion, respectively. The findings suggest the promise of combining shellac and SDS for delivering curcumin in acidic beverages.