The effects of LED illumination spectra and intensity on carotenoid content in Brassicaceae microgreens Aušra Brazaityte ˙ a,⇑ , Sandra Sakalauskiene ˙ a , Giedre ˙ Samuoliene ˙ a , Jule ˙ Jankauskiene ˙ a , Akvile ˙ Viršile ˙ a , Algirdas Novic ˇkovas b , Ram  unas Sirtautas a , Jurga Miliauskiene ˙ a , Viktorija Vaštakaite ˙ a , Laurynas Dabašinskas b , Pavelas Duchovskis a a Institute of Horticulture, Lithuanian Research Centre for Agriculture and Forestry, Kaunas Str. 30, LT-54333 Babtai, Kaunas Distr., Lithuania b Institute of Applied Research, Vilnius University, Saule ˙ tekio al. 9-III, LT-10222 Vilnius, Lithuania article info Article history: Received 17 June 2014 Received in revised form 3 October 2014 Accepted 15 October 2014 Available online 22 October 2014 Keywords: Carotenoids Irradiance level Light-emitting diodes Light spectrum Microgreens abstract The objective of this study was to evaluate the effects of irradiance levels and spectra produced by solid- state light-emitting diodes (LEDs) on carotenoid content and composition changes in Brassicaceae micro- greens. A system of five high-power, solid-state lighting modules with standard 447-, 638-, 665-, and 731-nm LEDs was used in the experiments. Two experiments were performed: (1) evaluation of LED irra- diance levels of 545, 440, 330, 220, and 110 lmol m À2 s À1 photosynthetically active flux density (PPFD) and (2) evaluation of the effects of 520-, 595-, and 622-nm LEDs supplemental to the standard set of LEDs. Concentrations of various carotenoids in red pak choi and tatsoi were higher under illumination of 330– 440 lmol m À2 s À1 and at 110–220 lmol m À2 s À1 in mustard. All supplemental wavelengths increased total carotenoid content in mustard but decreased it in red pak choi. Carotenoid content increased in tat- soi under supplemental yellow light. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction Vegetable crops contain various phytochemicals that are impor- tant for normal health maintenance and nutrition of humans. One important class of phytochemicals is the carotenoids (Kopsell & Kopsell, 2006). Carotenoids are yellow, orange, or red isoprenoid pigments synthesised by all photosynthetic organisms and some bacteria and fungi but not by mammals (Botella-Pavia & Rodriguez-Concepcion, 2006; Cuttriss, Cazzonelli, Wurtzel, & Pogson, 2011; Flores-Perez & Rodriguez-Concepcion, 2012; Kopsell & Kopsell, 2006). According to various sources in the liter- ature, 500–700 carotenoids have been identified in nature, and 40 of them are regularly consumed by humans (Kopsell & Kopsell, 2006; Stahl & Sies, 2005). Two structural groups of carotenoids are found in human plasma and tissues. The oxygenated carote- noids, such as lutein, violaxanthin, neoxanthin, and zeaxanthin, are called xanthophylls, and hydrocarbon carotenoids, such as b- carotene, a-carotene, and lycopene, are called carotenes (Botella- Pavia & Rodriguez-Concepcion, 2006; Flores-Perez & Rodriguez- Concepcion, 2012). Generally, carotenoids are characterised by such functions as free-radical scavenging, enhancing the immune response, suppressing cancer development, and protecting eye tis- sues, but individual carotenoids differ in their protective roles. a- Carotene, b-carotene, and cryptoxanthins, which are pro-vitamin A carotenoids, are mostly associated with cardiovascular disease reduction. Zeaxanthin and lutein are components of the macular pigment in the eye and protect the macula from light-induced damage. Lycopene prevents cardiovascular diseases and prostate cancer (Botella-Pavia & Rodriguez-Concepcion, 2006; Kopsell & Kopsell, 2006). In plants, carotenoids are light-harvesting pigments in chloro- plasts and are important in the protection of plants against photo- oxidative damage (Botella-Pavia & Rodriguez-Concepcion, 2006; Cuttriss et al., 2011; Lefsrud, Kopsell, Wenzel, & Sheehan, 2007). Their increase or decrease is influenced by environmental condi- tions during growth and show different results for different plant species (Kopsell & Kopsell, 2006). As carotenoids are closely related to photosynthesis, the most important factors impacting caroten- oid content changes are light quantity and quality. According to the literature, in general, sun-exposed leaves accumulate signifi- cantly greater amounts of carotenoids of the xanthophyll cycle and of b-carotene, but such leaves do not contain a-carotene or have smaller amounts than that found in shaded leaves (Czeczuga, 1987; Demmig-Adams & Adams, 1992; Demmig- Adams, Gilmore, & Adams, 1996). In addition, other authors http://dx.doi.org/10.1016/j.foodchem.2014.10.077 0308-8146/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +370 37 555 476. E-mail address: a.brazaityte@lsdi.lt (A. Brazaityte ˙ ). Food Chemistry 173 (2015) 600–606 Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem