Interactions of buttermilk with curcuminoids

The ability of buttermilk to carry and stabilise a preparation of curcuminoids was examined. The quenching of intrinsic protein fluorescence confirmed that the curcuminoids interacted with proteins in buttermilk. The Stern-Volmer quenching constant was ⩾9.4 × 103 M-1. The apparent binding constant of curcuminoids to whole buttermilk was ⩾2.2 × 104 M-1. Centrifugation of buttermilk (5% total solids, TS) - curcuminoid mixtures demonstrated that curcuminoids were partitioned into the cream (18.0% w/w, 0.64% TS), milk serum (73.3% w/w, 2.86% TS) and the casein-rich precipitate (6.76% w/w, 1.87% TS) fractions in the ratio of 1:3.7:3.5. The interaction of curcuminoids with components in the buttermilk improved its stability, as evidenced by the faster degradation of curcuminoids in phosphate buffer (pH = 6.8) than in buttermilk. The ability of buttermilk to carry and stabilise curcuminoids has the potential to enable the delivery of these components into functional foods.