Light-emitting diodes (LEDs) effect on the quality of ‘Carmine Jewel’ cherries during postharvest storage

Dwarf sour cherry (Prunus cerasus L.) is a cold-hardy, short-statured pie cherry released by the University of Saskatchewan. The cherries have higher sugar and acid contents than the pie cherries and may have market potential. In this study, we assessed the influence of blue and red light-emitting diodes (LEDs) on sour cherry ‘Carmine Jewel’ over a 3-week storage period in a walk-in cooler maintained at a temperature of − 2 °C. Both red and blue LED treatments increased the sour cherry rate of mass loss and soluble solid contents by 0.5−1.5 °Brix and pH by 0.05, but decreased the total acidity by 0.3% after 24 days of storage. In the meantime, LEDs influenced the color of the sour cherry skin. Compared to the dark treatment, the sour cherries had a lighter skin color (lower lightness (L*)). The red LED also significantly increased the red-blue (a*) parameters, resulting in a redder and brighter color. However, red LEDs might negatively influence the firmness, whereas blue LEDs did not significantly affect the firmness of sour cherries. For the secondary metabolites, both LEDs caused a significant increase in total phenolics in sour cherries after 24 days of storage. Blue LEDs appeared to influence this increase during the early storage period, specifically on days 3 and 6. Both red and blue LEDs consistently increased the anthocyanin content and ascorbic acid levels during storage, with more than 8 mg/L anthocyanins and 1−20 μg/mL ascorbic acids compared to the content under dark treatment after storage. The characteristics suggest that red and blue LEDs may play essential roles in the changes of primary and secondary metabolism. Anthocyanin compounds in sour cherries, including cyanidin-3-rutinoside, cyanidin-3-glusosylrutinoside, and cyanidin-3-glucoside, showed no changes in the dark treatment but were significantly increased under red and blue LEDs, with the red impact being larger. Cyanidin-3-sophoroside increased under dark treatment, but both LEDs had a more significant influence on its content, especially under the red LEDs. Neither red nor blue LEDs significantly influenced the microbial populations, although there was more than a 1.5 (lg (CFU/g)) increase in mold and yeast growth during storage. Similarly, both LEDs increased weight loss, which is not preferred for postharvest storage. This indicates the need to optimize radiation duration and light intensity in further studies. Therefore, LEDs can help improve certain qualities of sour cherries, and further adjustments are needed to achieve additional improvements.