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. beta-carotene-5,6-epoxide, beta-carotene-5,8-epoxide, beta-carotene-5,6,5',6'-diepoxide, beta-carotene-5,6,5',8'-diepoxide and P-carotene 5,8,5',8'-diepoxide were formed by the reaction of beta-carotene with MCPBA. The oxidation products with KMnO4 were identified as beta-apo-8'-carotenal, beta-apo-10'-carotenal, beta-apo-12'-carotenal, beta-apo-14'-carotenal and beta-apo-15-carotenal, along with semi-beta-caroten one and monohydroxy-beta-carotene5,8-epoxide. Except for beta-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. (c) 2006 Elsevier Ltd. All rights reserved.1012563572