Abstract:In order to comprehensively utilize the colored tomatoes, the carotenoid compositions of tomatoes in different colors were compared. The thermal stability of carotenoids was assessed, and the rules of isomerization and degradation were discussed. High-performance liquid chromatography- diode array detector(HPLC-PDA) with YMC Carotenoid C30 column was employed to separate carotenoids from tomatoes, and individual isomers were identified by the spectral characteristics.In addition, the effects of thermal treatment on the isomerization and degradation of carotenoids were investigated. The results showed that orange tomato-1 (OT-1) was rich in cis-lycopene (mainly 7,9,7’,9’-tetra-cis(7Z,9Z,7’Z,9’Z)), while orange tomato-2 (OT-2) was abundant in all-trans- (all-E-) β-carotene. The red tomato was rich in all-E-lycopene. The cis-lycopene content of OT-1 was 28.79 times and 12.57 times of that in OT-2 and red tomato, respectively. The total amount of phytofluene and phytoene was 7.52 times and 3.20 times of that in OT-2 and red tomato, respectively. In OT-1, the lycopene concentration decreased with the increment of heat time (0 ~ 5 h) and temperature (60~100 ℃). The value decreased to 1/3 of the initial content after treated at 100 ℃ for 3 h. Meanwhile, the 7Z,9Z,7’Z,9’Z isomer reduced significantly, which was not detected when treated at 100 ℃. However, the all-trans (all-E), 5-cis(5Z) and other cis-lycopenes increased to 28.51%, 28.73% and 42.76%, respectively. Heat treatment had no significant effect on the degradation and isomerization of lycopene and β-carotene in OT-2 and red tomato -P>>0.05). Besides, the retention rates of phytofluene and phytoene in OT-1 after treatment at 100 ℃ for 3 h still reached 84.32% and 88.76%. The results indicated that OT-1 was good source with high contents of cis-lycopene, phytofluene and phytoene.7Z,9Z,7’Z,9’Z-lycopene was less thermally stable than all-E lycopene and all-E-β-carotene, while phytofluene and phytoene showed better thermal stability. The above information is of great significance for the comprehensive utilization of tomato sources in different colors and the development of tomato products with high bioactivity.
