Antioxidants are believed to be important in the prevention of diseases such as cancer and cardiovascular disease. Lycopene is one of the main antioxidants to be found in fresh tomatoes and processed tomato products. The lycopene content also accounts for the redness of the fruit, which is one of the main qualities for which industry and consumers now look. Other carotenes (such as β-carotene), vitamin C, vitamin E and various phenolic compounds are also thought to be health-promoting factors with antioxidant properties. Since the antioxidant content of tomatoes may depend on genetic factors, the choice of variety cultivated may affect the results at harvest. To be able to control the antioxidant content of tomatoes at the field level when growing a given variety, it is necessary to know the effects of both environmental factors and the agricultural techniques used. Temperatures below 12 • C strongly inhibit lycopene biosynthesis and temperatures above 32 • C stop this process altogether. The effects of the temperature on the synthesis of other antioxidants have not yet been properly assessed. The effects of light have been studied more thoroughly, apart from those on vitamin E. The effects of water availability, mineral nutrients (nitrogen, phosphorus, potassium and calcium) and plant growth regulators have been studied, but results are sometimes contradictory and the data often incomplete. During the ripening period, lycopene content of tomatoes increases sharply from the pink stage onwards, but no sufficient attempts have been made so far to assess the changes in the other antioxidants present in the fruit. This paper reviews the present state of the art.

M. 2005. Effect of photoselective filters on the physical and chemical traits of vine-ripened tomato fruits. Can. J. Plant Sci. 85: 439-446. The effects of several wavelength selective light filters placed on developing mature green tomato fruits were studied to determine whether light environment during fruit ripening has an impact on fruit composition. Juice titratable acidity and fruit fresh and dry weight varied little with the different filters. Reducing the red/far-red light ratio with a green filter to simulate vegetation shade slightly delayed ripening. Reducing infrared light (700-1100 nm) reduced vitamin C and soluble sugars content. A drastic reduction in photosynthetic light (97%) reduced both β-carotene (-23%) and lycopene (-29%) contents and red coloration (-21%). Significant correlations were found among the content of soluble sugars, vitamin C and lycopene, but these components increased differently according to the spectral composition of the light transmitted to the fruit. The content of lycopene and β-carotene increased with exposure to photosynthetic radiation and more precisely with exposure to blue light. In contrast, the content of vitamin C and sugar increased with infrared light exposure. . L'effet de filtres sélectifs de différentes longueurs d'onde placés sur des fruits de tomate verts en maturation est étudié afin de déterminer si l'environnement lumineux durant la maturation des fruits influence leur composition. L'acidité titrable du jus et le poids frais et le poids sec sont peu modifiés par les différents filtres. La diminution du rapport rouge clair / rouge sombre avec un filtre vert simulant l'ombrage par la végé-tation retarde légèrement le mûrissement. Une diminution du rayonnement dans le proche infra-rouge (700-1100 nm) diminue la teneur en vitamine C et en sucres solubles. Une diminution importante du rayonnement photosynthétique (97%) diminue à la fois les teneurs en β-carotène (23%), lycopène (29%) et la coloration rouge des fruits (21%). Les teneurs en sucres solubles, vitamine C, et lycopène sont corrélées mais augmentent différemment selon la composition spectrale du rayonnement transmis au fruit. Les teneurs en lycopène et en β-carotène augmentent avec le rayonnement photosynthétique arrivant au fruit et plus particulièrement avec la quantité de lumière bleue. Par contre les teneurs en vitamine C et en sucres augmentent avec le rayonnement infra-rouge.

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