Characterisation of odour-active compounds in aged rum Jorge A. Pino a,⇑ , Sebastian Tolle b , Recep Gök b , Peter Winterhalter b a Food Industry Research Institute, Carretera al Guatao km 3½, Havana, C.P. 19200, Cuba b Institute of Food Chemistry, Technische Universität Braunschweig, Schleinitzstraße 20, DE-38106 Braunschweig, Germany article info Article history: Received 22 June 2011 Received in revised form 4 November 2011 Accepted 30 November 2011 Available online 8 December 2011 Keywords: Rum Gas chromatography–mass spectrometry Gas chromatography–olfactometry Aroma extract dilution analysis Odour activity value Solvent-assisted flavour evaporation abstract The volatiles of rum matured in oak casks were carefully isolated by solvent extraction followed by sol- vent-assisted flavour evaporation. Among the 116 volatile compounds identified by GC–MS, seven of them were found for the first time in rum. Application of the aroma extract dilution analysis (AEDA) on the volatile fraction revealed 18 odour-active areas in the flavour dilution factor range of 32–1024. On the basis of the quantitative data and odour thresholds in 35% ethanol (v/v), the odour activity values (OAV; ratio of concentration to odour threshold) were calculated. Nineteen aroma compounds showed OAVs >1, among which ethanol, (E)-b-damascenone, ethyl butanoate, ethyl hexanoate, vanillin, (Z)-oak lactone, ethyl 2-methylpropanoate, 1,1-diethoxyethane, ethyl 2-methylbutanoate, 3-methylbutyl ace- tate, ethyl octanoate, ethyl decanoate, 2-phenylethyl acetate, 2-phenylethanol, 2-methoxyphenol, 4- ethyl-2-methoxyphenol, 4-propyl-2-methoxyphenol, c-nonalactone, and eugenol showed the highest values and should be considered as the most odour-active compounds. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Rum is a fairly tasteless and neutral spirit, traditionally pro- duced in the Caribbean and Central America countries. It is mainly derived from the fermentation and distillation of sugar molasses, the black treacle-like substance which remains after sugar crystal- lisation. Once the alcohol is obtained from the fermentation and distillation processes, it undergoes further processing such as per- colation through carbon filters, ageing in oak barrels and blendings, which give rum its characteristic flavour (Nicol, 2003; Persad- Doodnath, 2008). In general, rums can be divided into two classes according to both colour and flavour: white (rums are filtered to remove any colour gained during ageing) and dark or aged rums. Although both classes are representatives of rum flavour, undoubt- edly the aged rums possess the most balanced rum flavour (Persad- Doodnath, 2008). Similar to other distilled spirits, rum is organoleptically charac- terised by the content of many volatile compounds, also known as congeners, such as higher alcohols, esters, carboxylic acids, car- bonyl compounds, phenols, and furan derivatives, among others, which contribute to the peculiar flavour of the spirit (Cardoso, Bettin, Reche, Lima-Neto, & Franco, 2003; De Souza, Vásquez, Del Mastro, Acree, & Lavin, 2006; Herranz, De La Serna, Barro, & Mar- tin-Alvarez, 1990; Nascimento, Cardoso, & Franco, 2008; Nykänen & Nykänen, 1991; Pino, Marbot, Pérez, & Nuñez de Villavicencio, 1999; Pino et al., 2002; Pino, 2007; Queris, Pino, Martí, & Rodríguez, 2007; Sampaio, Reche, & Franco, 2008). This great diver- sity of compounds is produced through metabolic pathways and their genesis depends on many factors related to raw materials and the subsequent processes of fermentation, distillation and ageing, others are oak derived, while others depend on the type of technological treatment (Nicol, 2003; Persad-Doodnath, 2008). Nevertheless, only a smaller number of the so-called key odourants is obviously detected by the human odourant receptors (Schi- eberle, 1995). An approach to separate odour-active volatiles from the bulk of odourless food volatiles is the application of GCÀOlfac- tometry (GCÀO), odour activity values (ratio of concentration to odour threshold) or, more comprehensively, dilution to odour threshold techniques, such as aroma extract dilution analysis (Schieberle, 1995). Numerous publications have dealt with the identification of volatile components in rum so far (Cardoso et al., 2003; De Souza et al., 2006; Herranz et al., 1990; Nascimento et al., 2008; Nykänen & Nykänen, 1991; Pino et al., 1999, 2002; Pino, 2007; Queris et al., 2007; Sampaio et al., 2008), but only one study has made efforts to evaluate the aroma contribution of the volatile compounds. De Souza et al. (2006) used GCÀO with CharmAnalysis to detect b-damascenone, 1,1-diethoxyethane, ethyl 2-methylbutanoate, ethyl 2-methylpropanoate, ethyl but- anoate, oak lactone, vanillin and two unknown compounds as the most potent odourants in rum. Although dilution to odour thresh- old techniques are useful methods for the screening of important odourants in foods, these methods neither permit a study on the influence of the food matrix on odourant binding nor permit a study on the interactions of odourants when matching the overall odour impression of the food (Schieberle, 1995). 0308-8146/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodchem.2011.11.133 ⇑ Corresponding author. Tel.: +537 202 0983. E-mail address: jpino@iiia.edu.cu (J.A. Pino). Food Chemistry 132 (2012) 1436–1441 Contents lists available at SciVerse ScienceDirect Food Chemistry journal homepage: www.elsevier.com/locate/foodchem