The Use of Visible LEDs as Technology to Delay Postharvest Senescence of Vegetables: A Review

In the last decade, a lot of research works and reviews have evaluated the effect of LED treatments during the postharvest storage of green vegetables. The curious thing is that, for the same vegetable, some works have shown that LED treatments improve postharvest life, while other researches have shown the opposite. Knowledge of the effects of light on the postharvest metabolism of each vegetable is needed to understand such contradictory results and to develop appropriate applications of postharvest LED technology to improve product quality. In this review, the role of visible light in the regulation of the postharvest senescence of green vegetables will be discussed. The information obtained so far suggests that low-intensity visible light, either continuous or pulsed, can maintain the quality of green tissues after harvest by delaying the onset of senescence and/or by improving their nutritional quality. The results also showed that the effect of LED technology depends on the duration of treatment, the intensity and the quality of the light used, and the type of vegetable irradiated. Studies have shown that both, white and red light, are effective to delay senescence, whereas blue light primarily enhances the antioxidant system with little or no effect in delaying senescence. To date, the published evidence strongly suggests that phytochromes (photoreceptors activated by red light) and phytochrome-interacting factors (PIFs) are involved in the delay of postharvest senescence symptoms.