Contents lists available at ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem Cultivar-specific responses in red sweet peppers grown under shade nets and controlled-temperature plastic tunnel environment on antioxidant constituents at harvest Chembi Solomon Lekala a , Khalil Saber H. Madani c , Anh Dao Thi Phan c , Martin Makgose Maboko b , Helen Fotouo a , Puffy Soundy a , Yasmina Sultanbawa c , Dharini Sivakumar a,c, ⁎ a Phytochemical FoodNetwork Research Group, Department of Crop Sciences, Tshwane University of Technology, Pretoria West, 0001, South Africa b Agricultural Research Council – Roodeplaat, Vegetable and Ornamental Plants, Private Bag X293, Pretoria 0001, South Africa c Queensland Alliance for Agriculture and Food Innovation, Center for Food Science and Nutrition, The University of Queensland, Australia ARTICLE INFO Keywords: Capsicum annuum L. Growing condition Bioactive compounds Capsanthin Vitamin C Lutein ABSTRACT Antioxidant constituents such as carotenoids (capsanthin, phytoene, lutein, β-cryptoxanthin), polyphenols content (p-coumaric, ferulic, p-hydroxybenzoic, caffeic acid, sinapic acid, and quercetin-3-glucoside) and mar- ketable yield were investigated in 11 sweet pepper cultivars grown under controlled temperature plastic tunnel and white shade net. Marketable yield was not affected by either of the environments, while the interaction between cultivar and growing environment significantly affected the accumulation of antioxidant constituents. The principal component analysis illustrated that controlled temperature plastic tunnel improved the accumu- lation of carotenoid components and ascorbic acid and vitamin C content in most cultivars. On the contrary, white shade nets favoured the accumulation of phenolic compounds and ORAC activity in most cultivars. A strong correlation was noted between phytoene and carotenoid components in this study (capsanthin r = 0.60; P < 0.001; lutein r = 0.75; P < 0.001; β-carotene r = 0.78; P < 0.001) while ORAC correlated with phenolic compounds. Based on this study, it is possible to refine the choice of environment and cultivar to enhance individual antioxidant constituent groups to improve health benefits for consumers. 1. Introduction The fruit of red sweet pepper (Capsicum annuum L.), a member of the Solanaceae family, are a rich source of essential minerals, anti- oxidant compounds such as carotenoids (capsanthin, capsorubin, cap- solutein, lutein and β-carotene) (Gómez-García & Ochoa-Alejo, 2013), ascorbic acid and secondary metabolites such as phenolic compounds (ρ-coumaric, ferulic, sinapic, gallic and chlorogenic acids) and flavo- noids (quercetin D-glucoside, kaempferol) (Hallmann & Rembiałkowska, 2012). These antioxidant compounds have been as- sociated with numerous health benefits (Kaur & Kapoor, 2001). Re- search has shown that ripe peppers demonstrated higher antioxidant properties than green unripe peppers (Cervantes-Paz et al., 2012). Capsanthin and capsorubin are two prominent carotenoids (k-xantho- phylls) responsible for the red colour of sweet peppers (Hornero- Méndez, Gómez-Ladrón-de-Guevara, & Mínguez-Mosquera, 2000). The carotenoid components, β-carotene, α-carotene and β-cryptoxanthin are known as sources of provitamin A. In addition, the conjugated double bonds and cyclic end groups in carotenoids are important as supplementary pigments for photosynthesis and also in providing photo-protection (Bartley & Scolnik, 1995). Dietary phytoene and phytofluene are precursors of the coloured carotenoids and are cur- rently gaining popularity due to their antioxidant capacity (Meléndez- Martinez, Mapelli-Brahm, Benítez-González, & Stinco, 2015). Phenolic compounds in sweet peppers are predominantly found in the pericarp (skin) and are highly regarded as important compounds due to their free radical scavenging properties (Marín, Ferreres, Tomaäs-Barberaän & Gil, 2004). However, phenolic compounds are present in free or bound forms in fruit and vegetables; in the bound state they are joined to sugar molecules via O-glucosides (hydroxyl groups) or C-glucosides. Bound phenolics have shown higher antioxidant capacity than free phenolics (Liyana-Pathirana & Shahidi, 2006). Free phenolics are https://doi.org/10.1016/j.foodchem.2018.09.097 Received 21 June 2018; Received in revised form 11 September 2018; Accepted 16 September 2018 ⁎ Corresponding author at: Phytochemical FoodNetwork Research Group, Department of Crop Sciences, Tshwane University of Technology, Pretoria West, 0001, South Africa. E-mail address: SivakumarD@tut.ac.za (D. Sivakumar). Food Chemistry 275 (2019) 85–94 Available online 17 September 2018 0308-8146/ © 2018 Elsevier Ltd. All rights reserved. T