Quality of Different Coloured Tomatoes Depending on the Growing Season

Abstract

Abstract Tomatoes have been widely used in nutrition, as well as in nutritional medicine. Red tomatoes are used for the treatment of anaemia, they contain the antioxidant lycopene, and the high concentration of organic acids promotes digestion. Yellow tomatoes have valuable amounts of ß-carotene, the pigment that gives orange and yellow tomatoes their colour, and helps to neutralise free radicals that may damage cells. The size of brown tomatoes is smaller than an average tomato, but they are sweeter, due to higher concentration of fructose. Cherry tomatoes are among the smallest tomatoes commercially available, but they are known for being rich in carotenoids, lycopene and phenolic compounds. The aim of the study was to evaluate how the concentration of biologically active substances differs depending on the tomato growing season. The study examined four varieties of tomatoes (Bolzano F1 — yellow, Chocomate F1— brown, Encore F1 — red, Strabena F1— red cherry) grown in an industrial greenhouse “Mežvidi” (Latvia) using additional light. The concentration of biologically active substances (lycopene, ß-carotene, total phenolic compounds, and soluble solids) was determined in two vegetation periods — autumn (November) and spring (March). The obtained results showed that tomatoes harvested in autumn contained more biologically active substances than in spring, as many biological processes in plants occur more rapidly at the beginning rather than in the middle or at the end of the vegetation season. Therefore, the concentration of secondary metabolites in tomatoes is higher at the end of the season. In autumn, cherry tomatoes Strabena contained the highest amount of pigments, total phenols, and soluble solids, and therefore the taste index of this variety also was the highest. In spring, pigment concentration was significantly lower (on average by 20–30%), and phenols and soluble solids concentration (oBrix) was not significantly lower — on average by 2–4%. Of the large-fruit tomatoes, at the beginning of vegetation season (autumn), the highest amounts of pigments were in red tomatoes (Encore) — lycopene concentration 4.63 ± 0.04 mg·100 g−1; yellow tomatoes Bolzano were rich in phenolic compounds — 128.46 ± 3.25 GAE mg·100−1, and brown tomatoes Chocomate had the highest soluble solids concentration — 4.48 ± 0.05 oBrix. In spring, the concentration of biologically active substances was lower on average by 10–15%, regardless of the colour and variety of the tomato.