noun. A red carotenoid pigment, C₄₀H₅₂O₄, produced by certain bacteria, fungi, and green algae and found in wild salmon, trout, and some crustaceans. It is used in animal feed to impart color and as an antioxidant.

noun. A xanthophyll pigment that occurs widely in plants and animals, especially crustaceans.

"Unlike fish oil, krill oil contains higher levels of a potent antioxidant called astaxanthin, which in addition to its ability to fight free radicals and oxidative stress, also helps make krill oil less perishable than fish oil."

E161j  food colouring