The chemical stability of lycopene in 2 commercial tomato powders was evaluated during storage. Liquid chromatography and spectral analysis were used to determine lycopene loss and the formation of cis isomers and degradation products. Tomato powder products were stored at 6 and 45 °C or under fluorescent light for up to 6 wk. Several lycopene degradation products were tentatively identified in the initial and stored powders. After 6 wk at 45 °C, 60% of the lycopene was degraded. At lower storage temperatures the losses were about 30% after 6 wk.Mechanisms of loss appear to be both isomerization and oxidation.

The stability and antioxidant effectiveness of lycopene, a-carotene, and b-carotene were compared during oxidation of methyl linoleate at 37 and 60 °C. Two carotene concentrations, 80 or 160 mg/g of methyl linoleate, were used to determine a concentration effect. At 37 °C, the degradation rates were: lycopene > ␤-carotene > ␣-carotene.Lycopene and ␣-carotene inhibited hydroperoxide formation, lycopene being the more effective antioxidant. ␤-Carotene inhibited hydroperoxide formation at the lower concentration but did not show an antioxidant effect at the higher concentration. At 60 °C, the carotenes degraded 6 to 8 times faster than at 37 °C and did not show an antioxidant effect.BHT or ␣-tocopherol effectively suppressed the hydroperoxide formation and degradation of the carotenes.