The Effect of Melatonin and Ecklonia maxima Extract on Bruising Incidence and Physicochemical and Antioxidant Properties of Tomato Fruit During Shelf-Life

Tomato (Solanum lycopersicum L.) fruit is highly susceptible to bruising, a physiological defect that reduces market quality and quantity. However, there is limited information regarding postharvest technologies for reducing bruising damage in tomato fruit. Therefore, in this study, we evaluated, for the first time, the effectiveness of melatonin and Ecklonia maxima extract (SWE) technologies alone and in combination in reducing bruising and preserving the postharvest quality of tomato fruit. To achieve this, fully matured red fruits were bruised by dropping a 110 g steel ball from a 60 cm height onto the tomato surface. Thereafter, fruits were dipped into distilled water (control), an optimized amount of 100 µM of melatonin, 1% SWE, and their combination (melatonin followed by SWE) for 5 min. The treated fruits were stored at 24 ± 1 °C and 65% ± 5 for 12 days. Bruise incidence and physicochemical and antioxidant properties were determined during shelf-life at 3-day intervals. The results showed that the melatonin alone and in combination significantly (p < 0.05) reduced bruise area and weight loss compared to the control. After 12 days of shelf-life, bruise area was significantly reduced in tomatoes treated with SWE + melatonin (92.07 mm2) and melatonin alone (94.91 mm2) compared to the control (203.80 mm2). Similarly, weight loss % was significantly lower in tomatoes treated with SWE + melatonin (2.17%), melatonin (2.58%), and SWE (2.80%) compared to the control (3.21%). Fruit color lightness was significantly higher in fruit treated with SWE compared to the those treated with melatonin and SWE + melatonin and control fruit. The TSS was significantly lower in the control compared to biostimulant-treated fruit (3.87 vs. average 4.63°) on day 12. The effect on the oxidative stress markers and antioxidant properties was inconsistent during 12-day storage. The findings demonstrate the potential of melatonin and SWE as postharvest treatments for reducing bruise-associated quality deterioration in tomato fruit during ambient storage. Further studies are required to investigate the physiological and molecular mechanisms underlying these responses.