During twisting of the b-carotene backbone unpaired
spin density will develop in each half of the molecule,
reaching a maximum in the perpendicular transition state and
forming cyclic peroxides which may self-initiate autoxidation
reactions. The main stable products to thermal degradation are
higher molecular weight components, epoxy-b-carotenes, apocarotenals
and apo-carotenones, other low molecular weight
di- and tri-oxygenated compounds, probably including carboxylic
and/or peracids, and carbon dioxide (Mordi et al., 1993)
(Fig. 5). Marty and Berset (1990) suggested b-carotene degrades
by progressive shortening of the polyene chain by two carbon
atoms at a time. So, oxidative break of a double bond in the bcarotene
molecule leads to the formation of two carbonyl fragments
of which one may be colorless. Benevides et al. (2011)
studied b-carotene oxidation by ozone in organic model and
demonstrated that the oxidized isomers formed depends on the
oxidation agent.