Postharvest Biology and Technology 53 (2009) 1–10 Contents lists available at ScienceDirect Postharvest Biology and Technology journal homepage: www.elsevier.com/locate/postharvbio Modelling the level of the major glucosinolates in broccoli as affected by controlled atmosphere and temperature Rob E. Schouten a,∗ , Xiaobing Zhang a , Ruud Verkerk b , Jan A. Verschoor c , Els C. Otma c , L.M.M. Tijskens a , Olaf van Kooten a a Horticultural Supply Chains, Wageningen University, Marijkeweg 22, 6709 PG Wageningen, The Netherlands b Product Design and Quality Management Group, Wageningen University, 6700 EV Wageningen, The Netherlands c Group AFSG, Wageningen UR, P.O. Box 17, 6700 AA Wageningen, The Netherlands article info Article history: Received 1 December 2008 Accepted 8 March 2009 Keywords: HPLC Gas exchange Glucoraphanin Multi-response Biological variation abstract This study describes the effects of controlled atmosphere (CA) and temperature on glucosinolate (GLS) levels in broccoli. Gas exchange rates were measured in three climate rooms with twelve containers each holding 20 randomly selected broccoli (cv ‘1997’) taken from one large batch of broccoli during a three- week period. Broccoli heads were stored at three temperatures and subjected to four levels of O 2 and three levels of CO 2 . GLS were measured on individual broccoli heads using a HPLC-based protocol. Infor- mation about the GLS development over time was extracted by analysing ‘replicate’ broccoli containers (containers stored at the same temperature and gas conditions) that were removed periodically during the storage period. The most striking feature was the large variation in GLS concentrations at harvest with the propagation of variation over time clearly affected by CA and temperature. Decay of the four most important GLS over time was described by a sigmoid model based on the decompartmentalisation of the enzyme myrosinase that hydrolyses GLS. Gas exchange parameters were estimated using the standard gas exchange model; the parameters of the GLS decay were estimated using a batch model that describes the propagation of the GLS variation as function of O 2 , CO 2 , time, temperature, the average biological age and biological variation (R 2 adj 88%). This approach was used to study the effect of regular and modified atmosphere conditions on GLS keeping quality. Storage under regular atmosphere during chain simu- lation showed that the keeping quality for all four GLS is between four and seven days, while storage under 1.5 kPa O 2 and 15 kPa CO 2 showed a keeping quality of at least 14d, indicating that to preserve the nutritional quality of broccoli, MA packaging is a viable option. © 2009 Elsevier B.V. All rights reserved. 1. Introduction Broccoli (Brassica oleracea var. italica) combines high levels of vitamins, carotenes, dietary fibres, glucosinolates (GLS) and other phytochemicals. Broccoli is a highly perishable vegetable with a shelf-life of only a few days. Colour is one of the main external qual- ity attributes of broccoli. One of the main internal quality attributes is the level of GLS. The hydrolysis products of GLS are responsible for the characteristic flavour of brassicaceous vegetables (Drewnowski and Gomez-Carneros, 2000). More importantly, a body of evi- dence has formed that one group of GLS breakdown products, the isothiocyanates, protects against carcinogenesis, mutagenesis, and other forms of toxicity of electrophiles and reactive forms of oxygen. This is due to the induction of phase II detoxication enzymes and the simultaneous inhibition of phase I enzymes, ∗ Corresponding author. Tel.: +31 317 483527; fax: +31 317 484709. E-mail address: Rob.Schouten@wur.nl (R.E. Schouten). responsible for the activation of carcinogens (Jones et al., 2006). For instance, isothiocyanates have been implicated in mitochondria- meditated apoptosis in cancer cells (Tang et al., 2006), the reduction of developing cardiovascular problems such as hypertension and atheriosclerosis (Wu et al., 2004) and the defence of the skin against UV radiation (Talalay et al., 2007). Controlled atmosphere (CA) is a very effective method to retain the colour of broccoli (Schouten et al., 2009) and also seems to point to GLS retention. Rangkadilok et al. (2002a) found that the level of glucoraphanin (GR), the most abundant GLS in broccoli, was signifi- cantly higher with a CA treatment (1.5% O 2 and 6% CO 2 ) compared to regular atmosphere during 25 d storage. Also, modified atmosphere packaging (MAP) storage at 20 ◦ C for up to 10 d showed retention of GR levels compared to the control (regular atmosphere). Schreiner et al. (2007) found that MAP packaging (1% O 2 and 21% CO 2 ) is suitable to maintain GLS levels of mixed packaged broccoli and cauliflower for 7 d at 8 ◦ C. On the other hand, Winkler et al. (2007) simulated transport at either 1 or 4 ◦ C up to 28 d and marketing conditions at 8, 15 or 20 ◦ C for 3 d and found that GR levels were 0925-5214/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2009.03.001