In addition to antioxidants such as vitamin C, OPC, Q10, vitamin E, alpha-lipoic acid, selenium and others, beta-carotene plays a central role as an efficient antioxidant and is therefore added to butter and margarine to make it last longer.
Beta-carotene is just one of more than 400 carotenoids which naturally occur in plants and fruits and give them their colour. The special thing about it, however, is that it is most common of all.