Co-encapsulation of curcumin and piperine in whey protein isolate fibrils improves their water dispersibility and antioxidant activity

Abstract

In this study, whey protein isolate (WPI) fibrils prepared by acid heat treatment for different times (5, 10, 15, or 20 h) were used for the co-encapsulation and co-delivery of curcumin (Cur) and piperine (Pip). Co-encapsulation of both nutraceuticals in the fibrils significantly improved their water dispersibility, chemical stability, and antioxidant activity. For instance, the water dispersibility of Cur and Pip in native WPI solutions was around 47.0% and 47.5%, respectively. In contrast, the water dispersibility of the same two nutraceuticals in WPI fibrils (15 h treatment) was 94.3% and 66.6%, respectively. The nutraceutical-loaded WPI fibrils did not undergo significant flocculation or precipitation after 14 d storage at 25 °C. After encapsulation, the DPPH free radical scavenging ability of the Cur-Pip combination experienced a surge, rising from approximately 35.4% to 72.0%. The Stern-Volmer quenching constants (Ksv) of Cur-WPI (3.03 × 104 M−1) and Pip-WPI (7.08 × 104 M−1) were much smaller than those of Cur-WPI fibrils (3.88 × 104–4.69 × 104 M−1) and Pip-WPI fibrils (8.26 × 104–9.41 × 104 M−1), indicating that the nutraceuticals bind stronger to the protein fibrils than to the native protein molecules. In summary, WPI fibrils have the capability to encapsulate, protect, and deliver hydrophobic nutraceuticals, suggesting their suitability for application in functional foods and beverages.