Postharvest UV-B and Photoperiod with Blue + Red LEDs as Strategies to Stimulate Carotenogenesis in Bell Peppers

Abstract

Background: Our objective was to evaluate carotenoid accumulation in bell peppers during shelf life under different light conditions. Methods: Fruit stored for 6 d at 7 °C received a 9 kJ m−2 UV-B treatment, while non-UV-treated were used as control (CTRL). Subsequently, all peppers were disposed for a retail sale period of 4 d at 20 °C with a photoperiod of 14 h under fluorescent light (FL) + 10 h under darkness (D), FL, or blue + red LEDs (BR LED). Results: Total antioxidant capacity (TAC) was increased by the UV-B treatment and the photoperiods supplemented with FL and BR LED, which was directly related to the carotenoid content. In fact, CTRL peppers (225 mg β-carotene kg−1) under FL+BR LED showed an increase of ~33% of 13-cis-β-carotene, ~24% of all-trans-β-carotene, and ~27.5% of 9-cis-β-carotene compared to FL + D and FL + FL. Capsaicinoids showed an increase by ~22%, ~38%, and ~27% in the content of capsanthin, capsanthin laurate, and capsanthin esters, respectively, after the UV-B treatment, which was even enhanced after the LED-supplemented photoperiod by ~18% compared to FL+D. Conclusions: Illumination with BR LEDs + UV-B during the retail sale period nights is recommended to increase the bioactive content of bell peppers via carotenoid accumulation to 270 mg β-carotene kg−1.

Anything New under the Sun? An Update on Modulation of Bioactive Compounds by Different Wavelengths in Agricultural Plants

“…Angus) fruits, exposed to UV-B radiation (8.94 W m −2 , 19 min and 30 sec) 6 days after the harvest, and then kept under different light conditions for up to 4 days to simulate a retail sale period. The carotenoid profile highlighted that such a positive effect was particularly evident when UV-B treatment was followed by storage under fluorescent/blue-red LED day/night photoperiod [220].…”

UV and Visible Spectrum LED Lighting as Abiotic Elicitors of Bioactive Compounds in Sprouts, Microgreens, and Baby Leaves—A Comprehensive Review including Their Mode of Action

“…In fact, the wounding of fresh carrot has been demonstrated to be effective also in combination with UV-A, UV-B, and UV-C lighting, whose application has been related to the production of ROS and, consequently, to the production of antioxidant compounds to fight against such oxidative processes [18,19]. In this sense, a direct correlation has been found between the UV-B application and the biosynthesis of nutraceuticals, which was recently corroborated in red prickly pears [20], broccoli by-products [21], carrots [22], and red bell peppers [8,23] to enhance the accumulation of glucosinolates and sulforaphane, phenolics, and carotenoids, respectively. These studies showed that the external stress provoked by UV increases the transcription of genes (FMO GS-OX5 -flavin-monooxygenase glucosinolate S-oxygenase 5-and MYB51) involved in the biosynthetic pathway of glucosinolates [2], as well as the genetic code in charge of the secondary metabolism to counteract the ROS action when UV RESISTANCE LOCUS 8 (UVR8) is activated [24].…”

UV-B Radiation as Abiotic Elicitor to Enhance Phytochemicals and Development of Red Cabbage Sprouts

“…In this sense, UVR8, as main UV-B receptors, are in charge to activate several transcription factors, such as COP1 (linked to HY5), as main stimulator of the PHYTOENE SYNTHASE (PSY), the first enzyme of carotenogenesis [13,57,58]. This behaviour has been recently shown in red peppers after a UV-B dose of 6 kJ m −2 applied before a short retailing period, which increased by 20 % the carotenoid accumulation, especially in combination with a blue + red LED photoperiod during the nights at supermarkets [59].…”