MECHANISM OF FORMATION OF VOLATILE COMPOUNDS BY THERMAL-DEGRADATION OF CAROTENOIDS IN AQUEOUS-MEDIUM .2. LYCOPENE DEGRADATION

During heat treatment of lycopene suspension in water, several volatile compounds are produced in an oxidative process. Beside 2-methyl-2-hepten-6-one and citral, previously characterized as a degradation products of lycopene, 5-hexen-2-one, hexane-2,5-dione, 6-methyl-3,5-heptadien-2-one, and geranyl acetate were identified and pseudoionone was tentatively identified by GC-MS. The temperature effect and the kinetic study of nonvolatile compound formation show that during the degradation process all-trans-lycopene is partially isomerized to the cis-trans isomer, which may considered an end reaction product. The same studies relative to volatiles show that the main compounds isolated, 2-methyl-2-hepten-6-one, geranial, and pseudoionone, arise from all-trans-lycopene. Subsequent degradation of this latter compound gives 6-methyl-3,5-heptadien-2-one, and geranial is isomerized to neral. © 1990, American Chemical Society. All rights reserved.