Casein-alginate conjugates prepared from a transacylation reaction as novel nanocarriers of curcumin for enhanced loading capacity, pH stability, and bioaccessibility

Protein-polysaccharide conjugates are potential carriers to deliver polyphenols such as curcumin in beverages. In this study, the objective was to study properties of casein-alginate conjugates prepared using a transacylation reaction as carriers of curcumin. For encapsulation, 2 mg/mL conjugate was mixed with 0.5, 1.0, or 1.5 mg/mL curcumin at pH 13.0 for 1 h, followed by adjusting pH to 7.0, 4.6, and 3.0 and centrifugation. The treatments had an encapsulation efficiency of about 80%, and the loading capacity of 18–36% was higher than studies using other protein-polysaccharide conjugates. The encapsulation resulted from hydrophobic interactions between curcumin and casein and the capsule dispersions were stable during 30-day storage at 4 °C and with additional 0–500 mM NaCl. Nanoencapsulation did not change the antioxidant activity of curcumin and resulted in 57% bioaccessibility, much higher than <10% of pristine curcumin. This work may be significant to deliver hydrophobic bioactive compounds in functional beverages.