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

Abstract

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 curcumin 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.