Postharvest LED Treatment of Tomatoes Harvested at an Early Stage of Coloration

The tomato plant is one of the most important vegetable crops, with a global production of around 188 million tones. The greatest losses in quantity and quality occur during storage, transport, and sale. The aim of the study was to determine the effect of irradiation on the quality and storability of the tomato ‘Tomimaru Muchoo’. Fruit harvested at the turning ripening stage were illuminated for the first two weeks at 15 °C with four visible LED light spectra, with different percentages of blue, green, and red light (BGR). The illumination times were 4 and 8 h per day (hpd). After illumination, the tomatoes were stored at 20 °C in the dark for 4 weeks. Immediately after 14 d of illumination, all tomatoes were fully ripe, although they showed varying red color intensity. In addition, all fruit retained very good quality and freshness. During further storage at 20 °C, there was a gradual decrease in tomato quality. However, LED lighting helped delay softening, reduce rotting, and thus maintain better tomato quality. Longer daily irradiation (8 h) delayed tomato senescence to a greater extent than shorter irradiation (4 hpd). Comparing the spectra, the greatest reduction in softening and rotting occurred in tomatoes illuminated with the spectrum containing the highest amount of blue light (56%). These tomatoes also maintained the lowest color index (a*/b*) throughout storage at 20 °C, which was especially evident in tomatoes that had been illuminated for 8 hpd. The light treatment influenced the maintenance of higher levels of ascorbic acid and antioxidant activity in tomatoes. However, irradiation did not increase the polyphenol content of tomatoes or reduce the lycopene levels in the fruit. Overall, the results showed that LED irradiation during storage improves storability and affects the health-promoting components of tomato fruit. It is a promising tool for reducing losses of horticultural produce.