Stability of carotenoid extracts of gấc (Momordica cochinchinensis) towards cooxidation - Protective effect of lycopene on β-carotene

Momordica cochinchinensis, so-called gấc in Vietnam, is considered as a fruit with high nutritional potential. Its antioxidant property, due to a high concentration of carotenes (β-carotene and lycopene), is particularly estimated. In this study, we have investigated the degradation of carotene extracts obtained from gấc aril. These extracts were dispersed in the aqueous phase in Tween 80 micelles or were encapsulated into polylactic acid (PLA) particles. In both cases, carotenes were far less degraded than synthetic β-carotene. However, the degradation of lycopene was still rapid (around 1 mM lycopene degraded per hour), whereas β-carotene was almost not bleached. Moreover, in gấc, the cleavage of the β-carotene's molecule was situated nearer the extremity of the cycle than for pure β-carotene. It gave rise essentially to β-cyclocitral. For encapsulated β-carotene, the presence of PLA modified this site to the C9-10 bond which is the favoured cleavage site of pure β-carotene.We conclude that the presence of lycopene in gấc has a protective role on the molecule of β-carotene and modifies the cleavage site. However, the supramolecular structure is still very important in the orientation of cleavage as the encapsulation in PLA particles increases degradation and modifies the cleavage site.