**6. Challenges and limitations associated with the postharvest use of LEDs**

The postharvest use of LEDs has various benefits in maintaining and preserving the quality of horticultural crops (**Table 1**). However, some negative impacts are aligned with the use of this technology. Irradiation with LED lights has been reported to slightly reduce the mass of fruit and vegetables due to enhanced moisture loss [45]. The reason behind this moisture loss could be the selection of a specific, harmful wavelength and long duration or exposure of LEDs to horticultural crops. The opening of stomata can also be induced by postharvest irradiation with LED lights, and that may result in treated fruit and vegetables losing moisture. Most studies, including our recent ones, have demonstrated that postharvest application of either red or blue LED lights can improve nutritional quality and preserve the quality of horticultural crops without negatively affecting their mass [19, 20, 46]. The higher intensity, longer daily exposure, and continuous illumination have been reported to cause abiotic stress, resulting in higher mass loss; this, however, depends on the wavelength or LED light spectra used [47]. It is, therefore, very important to pay special attention when selecting the intensity, duration of exposure and spectral composition, or wavelength of LEDs to apply to a specific horticultural crop.

### **7. Conclusions**

This review has demonstrated why LEDs are considered a novel technology in the food industry. This technology is constantly improving, and its application holds great potential in horticulture for food preservation. Importantly, LEDs are cost-effective and environmentally friendly, release minimal radiant heat, and have a monochromatic nature, which allows the selection of specific wavelengths, while excluding unwanted wavelengths that sometimes result in producing radiant heat. The application of LEDs postharvest has been shown to accelerate or delay ripening, improve color development, enhance the phytochemical concentration, improve nutritional quality, extend shelf life, and prevent fungal spoilage of various horticultural crops. It has, however, been noted that the recent research is focusing only on carotenoidaccumulating crops, such as pepper and tomato, with minimal focus on other crops. A deeper understanding of how various light spectra affect various crops and how the intensity of light and the duration of illumination affect various fruit and vegetables, especially highly perishable ones, is required. Merging of certain wavelengths still requires serious attention; it is also important to investigate the response of various crops to various ratios of wavelengths to decide on the combination that yields better

results. Further studies are required to reduce moisture loss as a result of LED illumination; in this case, the application of edible coatings in different formulations after LED illumination may potentially mitigate this effect. The sensory acceptability of fruit and vegetables treated with LEDs postharvest, as well as a deeper understanding of the mechanism involved in the postharvest irradiation of LED lights, still needs to be further investigated. Lastly, research revealed that LEDs can enhance healthrelated compounds present in fruit and vegetables; however, further studies need to be conducted to determine optimal ratios or combinations of LEDs and investigate which one achieves this optimally without negatively affecting other quality parameters of these commodities.
