It is generally accepted that oxidation of carotenoids begins with epoxidation and cleavage to apocarotenals. However, systematic studies to demonstrate occurrence of these reactions are lacking. In this study, the products formed by epoxidation with m-chloroperbenzoic acid (MCPBA), oxidative cleavage with KMnO4 and autoxidation in model systems, in the presence and absence of light, at ambient condition were identified. The presence of oxidation products was also verified in processed products. β-carotene-5,6-epoxide, β-carotene-5,8-epoxide, β-carotene-5,6,5′,6′-diepoxide, β-carotene-5,6,5′,8′-diepoxide and β-carotene 5,8,5′,8′-diepoxide were formed by the reaction of β-carotene with MCPBA. The oxidation products with KMnO4 were identified as β-apo-8′-carotenal, β-apo-10′-carotenal, β-apo-12′-carotenal, β-apo-14′-carotenal and β-apo-15-carotenal, along with semi-β-carotenone and monohydroxy-β-carotene-5,8-epoxide. Except for β-carotene 5,6,5′,6′-diepoxide, these products were detected in the model systems. Some of these products were also found in mango juice, acerola juice and dried apricot. Increased Z-isomerization was also observed and Z-isomers of the oxidation products were detected. © 2006 Elsevier Ltd. All rights reserved.1012563572Britton, G., Carotenoids (1991) Methods in Plant Biochemistry, 7, pp. 473-518Britton, G., UV/visible spectroscopy (1995) Carotenoids vol. 1B: Spectroscopy, pp. 13-63. , Britton G., Liaaen-Jensen S., and Pfander H. (Eds), Birkhäuser Verlag, BaselDavies, B.H., Carotenoids (1976) Chemistry and biochemistry of plant pigments, pp. 38-165. , Goodwin T.W. (Ed), Academic Press, LondonEl-Tinay, A.H., Chichester, C.O., Oxidation of β-carotene. Site of initial attack (1970) Journal of Organic Chemistry, 35, pp. 2290-2293Enzell, C.R., Back, S., (1995) Carotenoids vol. 1B: Spectroscopy, pp. 261-320. , Britton G., Liaaen-Jensen S., and Pfander H. (Eds), Birkhäuser Verlag, BaselHandelman, G.J., van Kuijk, F.J.G.M., Chatterjee, A., Krinsky, N.I., Characterization of products formed during the autoxidation of β-carotene (1991) Free Radical Biology and Medicine, 10, pp. 427-437Henry, L.K., Puspitasari-Nienabe, N.L., Jarén-Galán, M., van Breemen, R.B., Castignani, G.L., Schwartz, S.J., Effects of ozone and oxygen on the degradation of carotenoids in an aqueous system (2000) Journal of Agricultural and Food Chemistry, 48, pp. 5008-5013Kanasawud, P., Crouzet, J.C., Mechanism of formation of volatile compounds by thermal degradation of carotenoids in aqueous medium. 1. β-Carotene degradation (1990) Journal of Agricultural and Food Chemistry, 38, pp. 237-243King, T.J., Khachik, F., Bortkiewicz, H., Fukushima, L.H., Morioka, S., Bertram, J.S., Metabolites of dietary carotenoids as potential cancer preventive agents (1997) Pure and Applied Chemistry, 69, pp. 2135-2140Marty, C., Berset, C., Degradation of trans-β-carotene during heating in sealed glass tubes and extrusion cooking (1986) Journal of Food Science, 51, pp. 698-702Marty, C., Berset, C., Degradation products of trans-β-carotene produced during extrusion cooking (1988) Journal of Food Science, 53, pp. 1880-1886Marty, C., Berset, C., Factors affecting the thermal degradation of all-trans-β-carotene (1990) Journal of Agricultural and Food Chemistry, 38, pp. 1063-1067Mercadante, A.Z., Steck, A., Pfander, H., Carotenoids from guava (Psidium guajava L.): isolation and structure elucidation (1999) Journal of Agricultural and Food Chemistry, 47, pp. 145-151Onyewu, P.N., Ho, C.T., Daun, H., Characterization of β-carotene thermal degradation products in a model food system (1986) Journal of the American Oil Chemists' Society, 63, pp. 1437-1441Ouyang, J.M., Daun, H., Chang, S.S., Ho, C.T., Formation of carbonyl compounds from β-carotene during palm oil deodorization (1980) Journal of Food Science, 45, pp. 1214-1217Rodriguez-Amaya, D.B., (1999) A guide to carotenoid analysis in foods, , ILSI Press, Washington DCSchiedt, K., Liaaen-Jensen, S., Isolation and analysis (1995) Carotenoids vol. 1A: Isolation and analysis, pp. 81-108. , Britton G., Liaaen-Jensen S., and Pfander H. (Eds), Birkhäuser Verlag, BaselSiems, E., Sommeburg, O., Schild, L., Augustin, W., Langhans, C.-D., Wiswedel, I., β-Carotene cleavage products induce oxidative stress in vitro by impairing mitochondrial respiration (2002) The FASEB Journal, 16, pp. 1289-1291