Contents lists available at ScienceDirect Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio Changes in the volatile profile of citrus fruit submitted to postharvest degreening treatment Sawsen Sdiri a,1 , José L. Rambla b,1 , Cristina Besada a , Antonio Granell b , Alejandra Salvador a, ⁎ a Centro de Tecnología Postcosecha del Instituto Valenciano de Investigaciones Agrarias (IVIA), Carretera Náquera-Moncada, Km. 4.5, 46113, Moncada,Valencia, Spain b Instituto de Biología Molecular y Celular de Plantas (CSIC-UPV), Universidad Politécnica de Valencia, Ciudad Politécnica de la Innovación, Edificio 8E, Ingeniero Fausto Elio s/n, 46022 Valencia, Spain ARTICLE INFO Keywords: Oranges Mandarins Ethylene Quarantine treatment Volatiles Aroma-active compounds SPME GC/MS ABSTRACT Despite citrus fruit are considered as non climacteric, ethylene is effectively used to accelerate external colour change of early-season citrus fruit in the Mediterranean area and is generally assumed to have no effect on internal fruit ripening. In this study we investigated if this postharvest degreening treatment has any effect on the volatile profile of early-season citrus fruit. The experiment was carried out under commercial conditions, thus a quarantine treatment was also simulated. Degreening of early-season citrus varieties (‘Navelina’ oranges (Citrus sinensis (L.) Osbeck), ‘Clemenules’ and ‘Oronules’ mandarins (Citrus reticulata Blanco) and three mutations of ‘Oronules’ namely ‘Prenules’, ‘Basol’ and ‘Clemenrubí’) with ethylene produced reproducible and variety- specific changes in the levels of fruit volatiles. The volatile profile in response to ethylene in ‘Oronules’ and ‘Clemenrubí’ presented quite dramatic changes with higher levels of some esters such as ethyl propionate and ethyl octanoate. The volatile profile of ‘Navelina’, ‘Prenules’ and ‘Basol’ was only slightly affected by ethylene exposure and Clemenules’ did not show significant differences in the levels of aroma active compounds between degreened and control fruit, as would be expected for non climacteric fruits. On the whole, the results indicate that despite citrus being a non climacteric fruit some aspects of its ripening could be still sensitive to external exposure to ethylene. 1. Introduction The plant hormone ethylene regulates many aspects of plant de- velopment and also coordinates plant responses to biotic and abiotic stresses in coordination with other hormones (Vanstraelen and Benková, 2012). One of the developmental processes more character- istically regulated by ethylene is the ripening in climacteric fruits (Klee and Giovannoni, 2011). Competence to ripening seems to depend on the activation of system II for ethylene treatment that wouldn’t occur in non climacteric fruit like citrus nor in climacteric fruit before the de- velopmental activation of important factors (McAtee et al., 2013). Early-season citrus fruit grown under the Mediterranean climates reaches internal maturity while the peel remains green thus requiring a degreening treatment in order to enhance external colour change. On the beginning of the season, degreening treatment is widely applied using exogenous ethylene application under standard conditions of temperature and relative humidity (Sdiri et al., 2012a). Ethylene exposure during degreening treatment has been shown to have no effect on neither the internal quality attributes nor on the levels of some bioactive compounds, consistent with citrus being non cli- macteric fruit (Martínez-Jávega et al., 2008; Sdiri et al., 2012b). The effect of postharvest treatments such as coating and storage on the volatile composition of fresh citrus fruit has been extensively in- vestigated (Hagenmaier and Shaw, 2002; Porat et al., 2005; Obenland et al., 2008, 2011; Tietel et al., 2010b). However only a very limited number of studies have been conducted on the effect of ethylene on the volatile profile of degreened fruit (Mayuoni et al., 2011), and no in- formation exists about the effect of postharvest treatments on the vo- latile compounds of early season citrus fruit. Fresh citrus fruit releases a complex combination of a subset of more than 300 volatile organic compounds (VOCs), which include hydro- carbon terpenes, alcohols, aldehydes, esters and ketones (Rouseff et al., 2009; González-Mas et al., 2011; Miyazaki et al., 2010). Although hy- drocarbon terpenes are the predominant chemical class within citrus volatiles, this fraction makes little contribution to the odor perception because of their high odor thresholds. Aldehydes and esters are classes of compounds with a higher impact on citrus aroma. Thus, aldehydes have long been described to contribute to the orange aroma with citrus- http://dx.doi.org/10.1016/j.postharvbio.2017.07.001 Received 5 May 2017; Received in revised form 26 June 2017; Accepted 2 July 2017 ⁎ Corresponding author. 1 These two authors contributed equally to this work. E-mail address: salvador_ale@gva.es (A. Salvador). Postharvest Biology and Technology 133 (2017) 48–56 0925-5214/ © 2017 Published by Elsevier B.V. MARK