Abstract
Light-emitting diodes (LEDs) are a promising light source to produce functional foods. In this study, we investigated the effects of LED irradiation patterns on anthocyanin content in broccoli sprouts. The results showed that, among red, green, and blue LEDs, monochromatic irradiation with blue LEDs was the most efficient. Mixed irradiation with red and blue LEDs was comparable to monochromatic irradiation with blue LED at the same photosynthetic photon flux density (PPFD). Additional blue LED irradiation during red LED irradiation was more efficient than the additional red LED irradiation. The amount of anthocyanins in the broccoli sprouts increased as the PPFD of the blue LED increased. Additionally, the dark period during the 40-h cultivation had no effect on the anthocyanin accumulation. Under pulsed irradiation, the anthocyanin content increased with a higher duty ratio. However, the pulse period did not affect the anthocyanin content within the range of 0.2-20 ms. When the total photon number was the same throughout the irradiation period, there was no difference in the effects of continuous and pulsed irradiation on anthocyanin content. These results suggested that longer irradiation with a higher intensity of blue LED light is important for efficient anthocyanin production in broccoli sprouts.
