Contents lists available at ScienceDirect Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio UV-B radiation hormesis in broccoli florets: Glucosinolates and hydroxy- cinnamates are enhanced by UV-B in florets during storage Arturo Duarte-Sierra, Syed Mohammad Munzoor Hasan, Paul Angers, Joseph Arul* Department of Food Science and Plant Research and Innovation Centre, Laval University, Quebec, QC, G1V 0A6, Canada ARTICLE INFO Keywords: Broccoli UV-B radiation Oxidative stress Glucosinolates Hydroxy-cinnamates Gene expression ABSTRACT Abiotic stresses are oxidative in nature and cause generation of reactive oxygen species (ROS) in plant bodies. Severe stresses can be harmful to the plant tissue, whereas sub-acute or lower doses of stresses could enhance or induce protective mechanisms, a biological phenomenon known as hormesis. The objective of this work was to examine the effect of hormetic as well as high doses of UV-B on the quality along with glucosinolate and hy- droxy-cinnamate contents in broccoli florets during storage. An UV-B dose of 1.5 kJ m -2 was found to be hormetic from the color retention response. Color development, weight loss and respiration rate were monitored during 21 d of storage at 4 °C. The gene expression of dihomomethionine N-hydroxylase (CYP79F1), tryptophan N-hydroxylase 2 (CYP79B3), phenylalanine N-hydroxylase (CYP79A2), phenylalanine ammonia-lyase (PAL), chalcone synthase (CH) and flavanone 3-hydroxylase (F3H1) in the treated broccoli was also evaluated. The antioxidant capacity and the profiles of glucosinolates and hydroxy-cinnamates were determined for up to 14 d in broccoli florets stored at 4 °C by LC–MS. The hormetic dose of UV-B was effective in delaying the yellowing of broccoli florets. The initial respiration rate of the florets treated with the hormetic and a high dose (7.2 kJ m -2 ) was significantly high. The antioxidant capacity of florets was higher in UV-B treated florets relative to the control. The titers of indole-type glucosinolates and hydroxycinnamates in broccoli were significantly (p < 0.05) higher with both doses of UV-B compared to the non-exposed florets. UV-B appears to exhibit balanced effects with respect to quality preservation and enhancement of phyto-compounds in broccoli florets. Results showed a good correlation between gene expression of CYP79B3, and the titers of indole glucosinolates in the treated broccoli florets, suggesting that the target of UV-B is likely to be the branch pathway of indole glucosinolates. 1. Introduction Broccoli is an excellent source of nutrients including vitamin C, folic acid, vitamin K, and essential minerals. It also contains powerful health- promoting phytochemicals and antioxidants, including glucosinolates, the organo-sulfur compounds, phenolic acid derivatives, and flavonols (Duarte-Sierra et al., 2012, 2019). It is increasingly appreciated that a significant correlation exists between the intake of these phyto-com- pounds and protection against cancer and cardiovascular diseases (Fahey et al., 1997). Broccoli has become an important vegetable in the human diet worldwide due to its health-promoting properties and its high nutritional value. Nevertheless, the levels of glucosinolates (GLS) tends to decrease in the edible parts of the vegetable after it is detached from the source plant, and more importantly, during its postharvest storage (Schouten et al., 2009). They are also a part of the defense mechanisms against diseases in Brassicas and may be triggered by biotic as well as abiotic stresses (Doughty et al., 1995; Pereira et al., 2002; Textor and Gershenzon, 2009). Abiotic stresses are environmental factors that are of particular importance because of their negative impact on the yields of industrial crops worldwide (Gong et al., 2013). The most common abiotic stresses encountered during the production of fruit and vegetables are drought, nutrient deficiencies, extreme temperatures, salinity and light (Toivonen and Hodges, 2011). In the presence of one or more of these stresses, plants respond to them at the molecular, cellular, tissue, ana- tomical and morphological levels in order to cope with the unfavorable conditions (Fraire-Velázquez et al., 2011). At the molecular level, a cascade of events take place after the perception of a stress, which comprises cellular calcium spiking, cytoplasmic acidification, genera- tion of reactive oxygen species (ROS), generation of signals and signal transduction, kinase cascades, activation of transcription factors and gene expression leading to defense responses, including secondary metabolites, heat shock factors and PR proteins (Atkinson and Urwin, 2012; Zhao et al., 2005). https://doi.org/10.1016/j.postharvbio.2020.111278 Received 5 April 2020; Received in revised form 17 June 2020; Accepted 20 June 2020 ⁎ Corresponding author. E-mail address: joseh.arul@fsaa.ulaval.ca (J. Arul). Postharvest Biology and Technology 168 (2020) 111278 0925-5214/ Crown Copyright © 2020 Published by Elsevier B.V. All rights reserved. T