Functional, Flavor and Visual Traits of Hydroponically Produced Tomato Fruit in Relation to Substrate, Plant Training System and Harvesting Time

Currently, a great portion of tomatoes is produced by soilless cultivation systems and the substrate selection among the various materials is one of the most important factors affecting yield and quality traits. On the other hand, grafting has been successfully used in soilless systems to ensure long-term cultivation. However, due to the high cost of grafted seedlings, plant training systems are sought. Given the fact that most literature refers to studies intended to mainly reveal production differences among treatments and the quality aspect was secondary, the present study was focused on the evaluation of tomato fruit functionality, flavor and visual traits. Tomato plants cv ‘Beef Bang F1’ were cultivated in a glasshouse hydroponic culture in four substrates: rockwool slabs, perlite in sacks, pumice in sacks and pumice in 9 L pots. The type of cultivated plants used were self-rooted or grafted onto ‘Defensor’ trained in single and double stems. Tomato fruit were harvested three times during the season (6 June, 31 July, 6 November). The fruit quality was measured based on visual (average fruit mass, and Minolta color values), flavor (dry mass, soluble solids content, titratable acidity, pH, flesh firmness) as well as functional traits (total phenolic content, ascorbic acid, lycopene, β-carotene, total carotenoid content and antioxidant capacity). Harvest time was the most important factor followed in many of these cases by the substrate (flavor and functional traits), as well as in certain cases by the plant grafting/training (flavor traits and antioxidants) or by both in some flavor traits and antioxidants. Correlation of color values with lycopene, though significant, was weak. Each individual harvest time revealed the rise in different parameters. Pumice, whether used in pot or in sack, enhanced the visual and flavor attributes the most, self-rooted plants and mid-summer harvest resulted in the highest tomato fruit quality.