Known amounts of milk pigmented with astaxanthin oleoresin (4 g) were mixed with 2 mL DMSO and 3 mL of acetone, 2 mL brine solution and 2 mL n-hexane in a 15 mL conical tube. The mixture was shaked with vortex for 15 s and the tube was centrifuged at 2147×g for 3 min.