EFFECT OF RIPENING STAGE ON LYCOPENE CONTENT OF DIFFERENT PROCESSING TOMATO CULTIVARS GROWN IN TUNISIA

Tomatoes have an exceptionally rich source of lycopene. This pigment responsible for the red colour of the tomato has received great interest during the last few years because of its antioxidant activity against free radicals responsible for many actual important diseases. The level of this compound in tomatoes is strongly influenced by several cultural practices and agronomic aspects, particularly the variety and ripening stage. Therefore, the effect of five ripening stages (green, yellow, pink, redripe and overripe) on skin and pulp lycopene content of three processing tomato cultivars (Chicago, Perfectpeel and Rio Grande) was studied. Additionally, correlations between colour indexes and lycopene content were investigated. The result showed that lycopene contents were not significantly different in the pulp and skin of studied tomato cultivars. However, the ripening stage influenced significantly and similarly the lycopene content of studied tomato cultivars. In both the tomato pulp and skin, lycopene accumulation started after yellow stage and increased sharply after pink stage until the redripe stage. In overripe stage, lycopene content decreased significantly only in the tomato skin. Finally, correlation studies showed that the best estimation of lycopene content was obtained with the ratio (a*/b*)^².