Improvement of the colloidal stability of phycocyanin in acidified conditions using whey protein-phycocyanin interactions

Abstract Phycocyanin, a natural blue colorant from Spirulina, can form aggregate and precipitate in acidified beverages. In order to solve the aggregation problem of phycocyanin at low pH, we used whey protein to improve the stability of phycocyanin in acidified conditions. Our results showed that whey protein is much more effective compared to pea and egg white proteins in preventing the aggregation of phycocyanin at pH 3.0, in which a minimum 10% of whey protein solution is required to completely prevent the aggregation. In addition, undenatured whey protein is more effective compared to denatured and hydrolyzed forms. We found that α-lactalbumin, β-lactoglobulin, BSA, immunoglobulins, and glycomacropeptides may all participate in the encapsulation of the phycocyanin molecule. The Fourier transform infrared spectroscopy, native-polyacrylamide gel electrophoresis, and zeta-sizer results also proved that the complete whey protein provides better protection for phycocyanin compared to BSA or whey protein without the glycomacropeptides. The study provides a natural way to stabilize phycocyanin at acidified conditions, making it possible to use phycocyanin as a blue colorant in acidified beverages.