The study was conducted in the greenhouse of the company Paradajz d. o. o. in Renkovci on a cluster tomato variety grown in an integrated way on a hydroponic system, on growing slabs made of coconut fibre and peat. The aim of the study was to determine the time of onset of technological ripeness based on measurements of morphological and biochemical changes in the fruit during ripening. The measurements were carried out on fruits in two stages of ripening, fully red and orange-coloured fruits. In early spring (April–May), the degree of fruit ripeness was also determined from the beginning of flowering to technological ripeness. Technological ripeness was determined using a colour index and measurements of the content of sugars, organic acids, vitamin C, carotenoids, especially lycopene and phenolic compounds. No significant differences in sugar content were found between red and orange fruits. Orange fruits had a significantly higher content of malic acid and fumaric acid compared to red fruits. The red fruits reached the desired ratio between the colour parameters a and b (0.99) and were marketable, while the orange fruits reached the lower limit (0.60) of the parameter values for assessing marketability. The content of carotenoids, especially lycopene, was significantly higher in the red fruits than in the orange fruits. The ripeness class of the fruit had no influence on the content of vitamin C and phenolic compounds, with the exception of dihydrochalcones and flavanones, which were significantly higher in red fruit than in orange fruit. The weather conditions are decisive for the speed of ripening and colouring of the fruits. The first tomatoes reach technological ripeness 12–13 weeks after the first flowering.
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