Carotenoid content, antioxidant capacity and volatile compounds of the aroma during tomato ripening

Abstract

During ripening, tomato fruit accumulates high levels of carotenoids. These compounds, besides their function as pigments, nutrients and antioxidants, are precursors of some important volatile compounds for the development of the characteristic aroma of these fruits. In the present work, the antioxidant capacity, lycopene and β-carotene levels, and the production of aromatic substances derived from the carotenoid biosynthetic pathway were analyzed in the tomato cultivar 7705 at different ripening stages. Results showed a significant (p<0.05) increase of lycopene and β-carotene (22.1 and 2.9 fold, respectively) from the mature green to the breaker stage. Lycopene levels increased and those of β-carotene decreased from the light red to the red ripening stages. There was a 1.6 fold increase of the antioxidant capacity from the mature green to the breaker stage, with no changes between the light red to the red stage. The highest antioxidant capacity observed in the last stages of ripening correlated with the accumulation of lycopene and β-carotene pigments which participate in several antioxidant mechanisms. On the other hand, levels of the volatile compounds of the tomato aroma derived from the carotenoid metabolism significantly increased (p<0.05) in red tomatoes compared to mature green fruits (4.7 fold for 6-methyl- 5-hepten-2-one, 3.8 fold for damascenone and approximately twicefold for β-ionone and geranyl acetone). The increase in the volatile compoundss might be explained by the lycopene and β-carotene accumulation in the last ripening stages (light red and red), which are the precursors of the volatile apocarotenoids.