How Does Tomato Quality (Sugar, Acid, and Nutritional Quality) Vary with Ripening Stage, Temperature, and Irradiance? HÉLÈNE GAUTIER,* ,† VICKY DIAKOU-VERDIN, † CAMILLE BÉNARD, § MARYSE REICH, # MICHEL BURET, # FRÉDÉRIC BOURGAUD, § JEAN LUC POËSSEL, ⊥ CATHERINE CARIS-VEYRAT, # AND MICHEL GÉNARD † INRA, UR1115 Plantes et Systèmes de culture Horticoles, Domaine St. Paul, Site Agroparc, F-84914 Avignon, France, ENSAIA, UMR1121 Agronomie et Environnement, 2 Avenue Foret de Haye, F-54500 Vandoeuvre, France, UMR408 Sécurité et Qualité des Produits d’Origine Végétale, INRA, Université d’Avignon, F-84000 Avignon, France, and INRA, UR1052 Génétique et d’Amélioration des Fruits et Légumes, Domaine Saint-Maurice, F-84143 Montfavet, France The objective of this study was to understand the respective impact of ripening stage, temperature, and irradiance on seasonal variations of tomato fruit quality. During ripening, concentrations in reducing sugars, carotenes, ascorbate, rutin, and caffeic acid derivates increased, whereas those in titratable acidity, chlorophylls, and chlorogenic acid content decreased. Fruit temperature and irradiance affected final fruit composition. Sugars and acids (linked to fruit gustative quality) were not considerably modified, but secondary metabolites with antioxidant properties were very sensitive to fruit environment. Increased fruit irradiance enhanced ascorbate, lycopene, -carotene, rutin, and caffeic acid derivate concentrations and the disappearance of oxidized ascorbate and chlorophylls. Increasing the temperature from 21 to 26 °C reduced total carotene content without affecting lycopene content. A further temperature increase from 27 to 32 °C reduced ascorbate, lycopene, and its precursor’s content, but enhanced rutin, caffeic acid derivates, and glucoside contents. The regulation by light and temperature of the biosynthesis pathways of secondary metabolites is discussed. KEYWORDS: Ascorbate; carotene; fruit temperature; irradiance; phenolics; Solanum lycopersicum; sugars; tomato INTRODUCTION Fresh tomatoes are produced year-round in the greenhouse under contrasting environmental conditions, triggering seasonal variations in their gustative and nutritional quality (1–5). Fruit gustative quality fluctuates with the sugar/acid ratio, which generally increases during summer and decreases during winter. Little is known about the environmental regulation of tomato metabolites that are responsible for variations in fruit nutritional quality (6). Tomato contains carotenes (mostly lycopene and -carotene, a precursor of vitamin A), vitamin C, in its reduced form, ascorbic acid (AA) and its oxidized form, dehydroascorbic acid (DHA), and several phenolic compounds such as flavonoids (quercetin and kaempferol derivatives including rutin, and naringenin chalcone) and hydroxycinnamic acid derivatives [caffeic, ferulic and p-coumaric acid derivatives including chlorogenic acid (7)]. Several factors can affect these antioxidant concentrations, such as the ripening stage, cultivation practices (water availability, mineral nutrients), and climatic environment (mostly light and temperature (8)). Antioxidants play an important role by scavenging oxygen-active species generated during ripening (9), under excessive radiation (10) and cold or heat stress (11). Ascorbic acid and some phenolics tend to accumulate from the green to midripe stage, whereas the total carotenes increase constantly during the ripening process (8). Seasonal changes in phenolic contents (12) or ascorbate (13) have generally been related to light environment, probably due to their role in photoprotection (14). The soluble phenol content of plants grown under high light is approximately double the content of low-light plants (12). Similarly, transferring plants from shade to sunshine leads to increases of 66% of the ascorbic acid content of ripe fruits (15). However, ascorbate may also decrease with increased fruit solar exposure, probably due to increased ascorbic acid degradation with elevated temperatures (16). The effects of temperature on phenolics and ascorbate have not yet been properly assessed (8). Carotene biosynthesis is * Author to whom correspondence should be addressed [telephone +33 (0)4.32.72.23.45; fax 33 (0)4.32.72.22.82; e-mail gautier@ avignon.inra.fr]. † INRA, UR1115 Plantes et Systèmes de culture Horticoles. § ENSAIA, UMR1121 Agronomie et Environnement. # UMR408 Sécurité et Qualité des Produits d’Origine Végétale, INRA. ⊥ INRA, UR1052 Génétique et d’Amélioration des Fruits et Légumes. J. Agric. Food Chem. 2008, 56, 1241–1250 1241 10.1021/jf072196t CCC: $40.75  2008 American Chemical Society Published on Web 02/01/2008