Influence of the Species and Geographical Location on Volatile Composition of Spanish Oak Wood (Quercus petraea Liebl. and Quercus robur L.) EMILIA GUCHU, † M. CONSUELO DI ÄAZ-MAROTO,* ,† IGNACIO JAVIER DI ÄAZ-MAROTO, § PABLO VILA-LAMEIRO, § AND M. SOLEDAD PE Ä REZ-COELLO † A Ä rea de Tecnologı ´a de los Alimentos, Facultad de Ciencias Quı ´micas, Campus Universitario, 10 Universidad de Castilla-La Mancha, 13071 Ciudad Real, Spain, and Departamento de Ingenierı ´a Agroforestal, Escuela Polite ´cnica Superior, Campus Universitario s/n, Universidad de Santiago de Compostela, 27002 Lugo, Spain The influence of the species and geographical origin on the volatile composition of wood samples from 80 Spanish oaks (55 Quercus petraea Liebl. and 25 Quercus robur L.) has been studied. Oak volatile components were isolated by simultaneous distillation-extraction and analyzed by gas chromatography-mass spectrometry. cis- and trans--methyl-γ-octalactones were the main con- stituents, the cis stereoisomer being predominant. Other important volatile components were furfural, 5-methylfurfural, guaiacol, eugenol, vanillin, or syringaldehyde. The main differences were established between species, Quercus petraea being significantly richer in volatile compounds than Quercus robur; however, the variability found among trees was high. Differences among geographical provenances were much less important than those found between species. KEYWORDS: Oak; Quercus petraea; Quercus robur; geographical location; volatile compounds INTRODUCTION Approximately 250 species of the genus Quercus exist distributed all over the world. However, only three are used for aging wines: Quercus petraea (sessile oak), Quercus robur (pedunculate oak), and Quercus alba (American oak). Although France is presently the first producer of wood of European oaks (Q. petraea and Q. robur) for use in wine aging, these two species can also be grown in other zones of Europe, such as Spain, Portugal, Hungary, or Russia. The chemical composition and sensorial characteristics of wood of French oaks have been widely studied, and a high variability between species, geographic provenance, and indi- vidual trees has been found (1-9). Volatile component con- centrations are usually greater in wood of Q. petraea oak than in Q. robur oak (8). Many volatile compounds have been found in oak wood, but only a few of them are significant because of their impact in the sensory characteristic of wines. cis- and trans- -methyl-γ-octalactones (oak lactones) have been described as being responsible for the oak flavor and having a low perception threshold (10, 11). Vanillin is the only aldehyde related to lignin that exerts some effect on the aroma of wines aged in oak. Small free phenols such as eugenol and guaiacol provide spice and smoke attributes (12). Oaks from central Europe (Bulgaria and Hungary) and Russia are being used as alternatives to French oaks in the barrel- making industry; however, there is little information about these types of oaks in the literature. Dı ´az-Maroto et al. (13) studied the volatile composition of Hungarian and Russian oaks by solid-phase microextraction (SPME). However, because high variability between trees of the same species and provenance was found for French and Spanish oaks (7, 8, 14, 15), more studies are necessary to characterize these types of oaks. At the moment, Spanish oaks are not used commercially at great scale; nevertheless, studies realized on their chemical composition, as well as their behavior during the wine aging process, have made clear their possibilities as an alternative to the traditionally exploited French and American oaks (3, 14- 16). Spanish oak forests are spread all over the northern and northwestern regions of the Iberian peninsula. Therefore, to draw conclusions on the potential of the Spanish oaks as alternatives to the oaks traditionally used in the aging of wines, it is necessary to study the chemical composition of a larger sample set of Spanish oaks from different regions. Variability among trees of the same species or region and differences in the treatments applied to the casks must be taken into account when species are differentiated, and the sampling method employed is of great importance. Towey and Water- house (17) reported variabilities of 30% on the chemical * Author to whom correspondence should be addressed (telephone 00-34-926-295300, ext. 3424; fax 00-34-926-295318; e-mail MariaConsuelo.Diaz@uclm.es). † Universidad de Castilla-La Mancha. § Universidad de Santiago de Compostela. 3062 J. Agric. Food Chem. 2006, 54, 3062-3066 10.1021/jf053055z CCC: $33.50 © 2006 American Chemical Society Published on Web 03/22/2006