Formation of Carotenoid Oxygenated Cleavage Products - Carotenoids: Physical, Chemical, and Biological Functions and Properties - page 225

different oleoresins of paprika, tomato, and marigold (Rios et al. 2008). Two groups of compounds
were distinguished: cyclic olei ns with or without oxygen atoms and compounds qualii ed as “lin-
ear ketones.” In the i rst group, some of the compounds identii ed were hydrocarbons, such as
m-xylene, toluene, or 2,6-dimethylnaphtalene; others were oxygenated, such as methylbenzalde-
hyde, isophorone, loliolide or ethanone, and 1-methylphenyl was identii ed for the i rst time as a
carotenoid-thermodegraded compound. Two “linear ketone” type compounds were identii ed as
6-methyl-3,5-heptadien-2-one and 6-methyl-5-hepten-2-one. Intramolecular cyclization followed by
an elimination reaction in the chain or a heterocyclic fragmentation reaction and oxidation reactions
are mechanisms proposed to explain the occurrence of detected compounds.
Kanasawud and Crouzet have studied the mechanism for formation of volatile compounds by
thermal degradation of -carotene and lycopene in aqueous medium (Kanasawud and Crouzet

1990a,b). Such a model system is considered by the authors to be representative of the conditions
found during the treatment of vegetable products. In the case of lycopene, two of the compounds
identii ed, 2-methyl-2-hepten-6-one and citral, have already been found in the volatile fraction of
tomato and tomato products. New compounds have been identii ed: 5-hexen-2-one, hexane-2,5-
dione, and 6-methyl-3,5-heptadien-2-one, possibly formed from transient pseudoionone and geranyl
acetate. According to the kinetics of their formation, the authors concluded that most of these prod-
ucts are formed mainly from all-( E )-lycopene and not ( Z )-isomers of lycopene, which are also found
as minor products in the reaction mixture.

β

11.6 CONCLUSIONS
Carotenoid oxygenated cleavage compounds include many different chemical structures and can
be formed in various ways. Their inl uence on the organoleptic quality of food is well known, at
least for volatile compounds, and some of them have been identii ed as aroma compounds (e.g.,
pseudoionone). Except for retinoids, their occurrence in humans has not been proven to date, but
their biological effects, which could be either benei cial or detrimental for health, are well docu-
mented in vitro and strongly suspected in vivo (Wang 2004). Further research is needed to localize
them in vivo and to determine if they contain signii cant biological activity.

ACKNOWLEDGMENTS
I thank my collaborators Michel Carail and Eric Reynaud for their participation in the work
described and scientii c discussions.

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