Bioactive Compounds, Antioxidant Activity and Color of Hydroponic Tomato Fruits at Different Stages of Ripening

Abstract

This experiment was carried out in order to study the simultaneous effect of on-vine ripening and examined cultivars on fruit quality, color development and antioxidant content in two different types of tomatoes. ‘Admiro’ and ‘Komet’ (normal average fruit weight) and ‘Cheramy’ (cherry type) cultivars grown in hydroponic culture were used. Dry matter, soluble solids, titratable acidity, ascorbic acid, lycopene, b-carotene, total phenolic, total flavonoid content and hydrophilic antioxidant activity were measured in six ripening stages. Color of fruits was determined by CIELab system. The L*, a*, b* values were used to calculate hue angle (h^o), chroma (C*) and a* to b* ratio. In all analysed cultivars total phenolic content increased as ripening progressed, reached the maximum at the pink stage and subsequently declined, while the trend of ascorbic acid was cultivar dependent. DPPH radical scavenging activity showed significant moderately strong positive correlations with total phenolics and ascorbic acid. The content of β-carotene increased constantly during ripening while lycopene content registered a sharp rise, especially in the last stage of ripening when 47.2% of the lycopene content was accumulated. During ripening the lightness (L*) decreased because tomato fruit colour became darker while the ratio of red to green colour increased as a result of carotenoids synthesis. Among color indexes, hue angle (h^o) was best correlated with lycopene content (r = −0.758), followed by a* (r = 0.748), C* (r = 0.708) and a*/b* (r = 0.683). Better correlations were established between main carotenoids content (lycopene + b-carotene) and each of the color indexes.