Antioxidant properties of natural carotenoid extracts against the AAPH-initiated oxidation of food emulsions

The antioxidant effects of natural carotenoid extracts on the oxidation of oil-in-water emulsions (initiated by a water-soluble radical initiator at 60 degrees C) were spectrophotometrically assessed at 233 nm. Headspace volatiles were also monitored for selected samples. At concentration of 1 g l(-1) the tested carotenoids significantly reduced the oxidative deterioration of sunflower oil-in-water emulsions. The presence of polar groups was found to modulate the carotenoid activity. Annatto extracts (orbiting and bixin) containing carotenoids with carboxylic and esters groups, were more effective than marigold extract containing lutein (with two hydroxyl groups). beta-Carotene and a tomato (lycopene-rich) extract, (unsubstituted carotenes), were the least effective. For polar carotenoids, the antioxidant activity did not increase with concentration above a specific level. The tested carotenoids strongly inhibited the formation of volatile aldehydes. Mixtures of lutein or beta-carotene with tocopherol isomers increased the antioxidant activity of individual carotenoids. Mixtures of carotenoids with ascorbic acid at 0.1 g l(-1) exerted a tendency, not significant though, for increasing the activity of each individual carotenoid. (c) 2006 Elsevier Ltd. All fights reserved.