Volatile composition of oak and chestnut woods used in brandy ...

Fournier, & Puech, 1995; Miller, Howell, Michaelis, &
Dickman, 1992; Mosedale & Savill, 1996; Nabeta,
Yonekubo, & MiYake, 1986; Sefton, Francis, Pocock,
& Williams, 1993), the seasoning of the staves (Chatonnet,
1995; Sefton et al., 1993) and the toasting of the
barrel (Artajona, 1991; Canas, 2003; Chatonnet, 1995;
Chatonnet, Boidron, & Pons, 1989; Dubois, 1989;
Maga, 1985; Nishimura, Onishi, Masuda, Koga, &
Matsuyama, 1983; Nomdedeu et al., 1988; Sarni, Moutounet,
Puech, & Rabier, 1990).
In spite of a substantial knowledge about volatile
composition of French and American oak wood, few
data are available for others woods, namely chestnut
and oak Portuguese woods (Borralho, 1994; Clímaco &
Borralho, 1996) and from a cooperage point of view
the first chestnut wood results were presented in preceding
works (Canas, Leandro, Spranger, & Belchior, 1998,
1999). In our previous work, it was found that the brandies
aged from chestnut barrels presented a good quality
(Belchior et al., 1998; Caldeira et al., 1998) and higher
levels of some phenolic compounds (Canas, Caldeira,
et al., 1998; Canas, Leandro, Spranger, & Belchior,
1999).
The aim of this study is to characterise Portuguese
chestnut and oak wood comparatively with French
and American oak wood, using volatile composition
and also to point out the modifications induced by the
heat treatment, made during the cooperage process.
2. Material and methods
2.1. Experimental design and wood sampling
A two factorial design (7 woods · 4 toasting levels · 2
replicates) was established and 56 wood samples were
taken.
The anatomical study (Carvalho, 1998) led to the
botanical identification of seven wood species: three
Portuguese oak wood, which were all Quercus pyrenaica
Willd. from three different sites in the north of Portugal
(CNE, CNF, CNG); two French oak wood, one from
Allier identified as Quercus sessiliflora Sallisb. (CFA)
and another from Limousin region identified as Quercus
robur L. (CFL); one American oak wood which was a
mixture of Quercus alba L./Quercus stellata Wangenh.
and Quercus lyrata Walt./Quercus bicolor Willd.(CAM)
and one Portuguese chestnut wood (CAST), from the
northern, identified as Castanea sativa Mill. From each
wood, six barrels were constructed, which were submitted
to heat treatment with 3 degrees of toasting: light
(QL), medium (QM) and strong (QF), with two replicates
of each. Before and after the toasting process of
the barrels, shaves were cut in order to get samples from
the wood. The two replicates of each wood, taken before
toasting, represent the fist level of toasting factor (Q0).
I. Caldeira et al. / Journal of Food Engineering 76 (2006) 202–211 203
The toasting process was controlled by the cooper 1 ,
which is about 10 min (light toasting), 20 min (medium
toasting) and 25 min (strong toasting) of slow toasting
the barrel, over a fire of the respective wood offcuts.
2.2. Wood extraction
Hydroalcoholic wood extracts were obtained with
50 g of milled wood (Hammer-Mill–Wiley) macerated,
under rotary agitation for 180 min at 20 °C, with
1000 mL of an ethanol–water solution at 55% v/v adjusted
to pH 4.2 with hydrochloric acid, according to
conditions previously selected (Caldeira, Pereira,
Clímaco, Belchior, & Bruno de Sousa, 2004).
The hydroalcoholic wood extracts were filtered
through a glass microfibre filter (Whatman GF/C) in a
Büchner funnel.
2.3. Wood moisture
The wood powder moisture was determined in a
moisture analyser (Mettler LJ 16-Switzerland).
2.4. Analysis of volatile compounds
The isolation of the volatile compounds, from the
hydroalcoolic wood extracts, was done by liquid/liquid
extraction with three successive aliquots of dichloromethane,
and the analysis of the compounds by GC
and GC–MS, was carried out as described by Caldeira
(2004) and Caldeira et al. (2004), with some modifications
on the GC conditions: each concentrated extract
was injected in a Carlo Erba 6000 Vega series equipped
with a flame ionisation detector (250 °C) and with a silica
capillary column (DB-WAX–J&W: 30 m-lengh,
0.32 mm-internal diameter, 0.25 lm-film thickness); elution
was carried out with hydrogen as carrier gas
(1.4 mL min 1 ); temperature program: 3.5 °C min 1
from 45 °C (5-min isothermal) to 210 °C (30-min isothermal);
the injector was at 250 °C, and approximately
0.8 lL was injected with a split ratio of 1:15.
Quantification was carried out by the internal standard
method; the response factor of volatile compounds
to the internal standard was arbitrarily fixed at 1.0 and
the results were expressed as lg/g of dry wood.
2.4.1. Reagents
All solvents used were analytical grade purchased
from Merck (Darmstadt, Germany) and the dichloromethane
were bidistilled.
2.4.2. Reference compounds
Acetic acid was purchased from Riedel-de-Haen (Seelze,
Germany); 2-methyl-1-butanol, 3-methyl-1-butanol,
1 Tanoaria J. M. Gonçaves, Palaçoulo-Portugal.