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

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Table 3 Contents of volatile compounds in aqueous alcoholic wood extracts and toasting intensity effect (results expressed as lg per g of dry wood) Compound Toasting effect Toasting intensity Q0 QL QM QF Acetic acid * x 38.36a 47.59ab 53.17b 58.94b SD 24.43 27.22 20.70 20.22 Furfural *** x 7.04a 53.00a 103.77b 223.91c SD 4.87 20.44 48.61 105.15 5-Methylfurfural *** x 0.32a 4.75a 13.86b 31.41c SD 0.35 2.36 7.20 12.55 4-Hydroxy-2-butenoic acid lactone *** x 0.62a 0.78a 1.58b 2.44c SD 0.71 0.67 0.77 0.84 5-Hydroxymethylfurfural *** x 1.40a 9.71b 21.48c 41.48d SD 1.02 5.04 9.16 17.93 Guaiacol ** x 0.73a 1.09a 0.84a 1.57b SD 0.58 1.18 0.38 0.76 Eugenol *** x 1.73a 2.39ab 2.49bc 3.07c SD 1.34 1.25 1.44 1.39 Syringol *** x 0.24a 0.32a 0.80a 3.67b SD 0.34 0.35 0.61 2.23 4-Allyl-syringol *** x 1.06a 1.83ab 2.75b 4.15c SD 0.79 1.07 3.04 1.54 Vanillin *** x 4.75a 13.82b 25.87c 46.60d SD 2.24 4.22 12.96 14.15 Acetovanillone * x 0.65a 2.37b 2.31b 2.21b SD 0.95 2.95 1.97 2.59 Propanoic acid *** x 0.38a 0.30a 0.52a 1.08b SD 0.42 0.38 0.36 0.55 Hexanoic acid * x 4.85b 3.42a 3.48ab 2.80a SD 4.93 2.40 2.00 2.05 trans-b-Methyl-c-octalactone n.s. x 2.18 3.10 3.10 3.79 SD 0.92 2.11 2.15 2.97 cis-b-Methyl-c-octalactone + 4-methyl-guaiacol * x 9.57a 15.79b 14.92b 16.37b SD 11.40 17.53 17.76 15.84 Octanoic acid n.s. x 2.59 2.92 1.92 1.92 SD 2.00 1.99 0.82 1.13 Decanoic acid n.s. x 1.41 2.07 1.31 1.72 SD 0.81 2.39 0.52 1.09 Dodecanoic acid n.s. x 2.15 4.02 2.41 2.54 SD 1.44 3.38 1.83 1.31 x, means of fourteen values; SD, standard deviation; means followed by the same letter in a row are not significantly different at the 0.05*, 0.01** or 0.001*** level of significance; n.s.: without significant difference. 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 Q0 QL QM QF Guaiacol/Syringol Eugenol/4-Allyl-syringol Fig. 6. Effect of toasting level on the guaiacyl/syringyl ratio on the all woods analysed. Concerning the amounts of guaiacol, the toasting level has a significant effect on this compound, as well as the interaction wood origin · toasting level. The guaiacol amount increases with toasting level in CAM and I. Caldeira et al. / Journal of Food Engineering 76 (2006) 202–211 209 CFL woods; on the other hand for CNG, CAST and CFA the toasting had no effect and for the other woods the behaviour are different. Further research is needed to evaluate this question, but we hypothesize that two phenomenonÕs occur simultaneously: formation of guaiacol as result of thermal degradation of lignin and also itÕs decrease due to its thermal degradation. The vanillin amount increases with toasting level and the higher levels are found in high toasted wood, as referred by others authors (Artajona, 1991; Canas, 2003; Nomdedeu et al., 1988) and in disagreement with Chatonnet et al. (1989). It was also possible to discriminate each level of toasting based on the amounts of this compound. Regarding acetovanillone, the toasting level has a significant effect on this compound, as well as the interaction wood origin · toasting level. In fact the toasting
210 I. Caldeira et al. / Journal of Food Engineering 76 (2006) 202–211 level had only effect on the contents of this compound for CNF and CFL woods. For the majority of the acids the toasting process does not affect their contents, except for hexanoic and propanoic acids. For the former it was found a decrease with the increase in the toasting level and also it was detected effect of interaction factors; so the toasting process only affected the hexanoic levels of five types of wood (CNF, CNG, CAST, CFA and CAM). Toasting effect and interaction effect was also detected for propanoic acid. For CNF, CAST and CFA the toasting level did not affect the propanoic acid contents, although in the other types of wood studied, higher toasting level increased the quantity of this compound. It can be also noted that the toasting level effect on the amounts of cis-b-methyl-c-octalactone + 4-methylguaiacol was significant, but for the trans-b-methyl-coctalactone the toasting do not affect itÕs contents, which disagree with the results obtained using French oak wood by Chatonnet et al. (1989). The principal component analysis (Fig. 5) shows that the initial wood group division, made by the first component, seems based on the toasting level, which increases across the component. In fact the unheated woods are located in the negative branch of this component, in opposite to the strongly toasted woods, which are located in positive branch of this component. Nevertheless it seems that the division between the successive toasting levels is not clear. This could be due to the strong variability resulting from many uncontrolled parameters during the heat treatment. The variables, which influence most the first component, are the furanic aldehydes (furfural, 5-methyl-furfural, HMF), 4-hydroxy-2-butenoic acid lactone, vannilin, propanoic acid and volatile phenols with a syringyl-type structure, namely syringol and 4-allyl-syringol. The increase in toasting level enhances the quantity of these compounds in wood. These results could explain the sensory significant differences found in the brandies aged, in these barrels (Caldeira, Belchior, Clímaco, & Bruno de Sousa, 2002). 4. Conclusions This present work permitted the identification, for the first time, of the 4-hydroxy-2-butenoic acid lactone in oak and chestnut wood, moreover, also for the first time, 2 + 3-methyl-1-butanol, benzaldehyde, acetovanillone, b-methyl-c-octalactone, guaiacol, 4-methylguaiacol, 4-propylguaiacol, 4-ethylguaiacol, eugenol, isoeugenol, 4-methylsyringol and 4-allyl-syringol were identified in chestnut wood. These results pointed out that the unheated wood discrimination is possible based on certain volatile compounds namely eugenol, cis-b-methyl-c-octalactone, furfural, 4-hydroxy-2-butenolactone, hexanoic acid and guaiacol. Nevertheless after the toasting process, wood discrimination is weaker and it is only possible to discriminate the American oak wood from the other types of wood based on amounts of eugenol and cis-bmethyl-c-octalactone present. For the seven woods studied, including the Portuguese chestnut, this work showed that the increase in the level of toasting is related to the increase in the levels of many compounds. The most affected were furanic aldehydes (furfural, 5-methylfurfural, HMF), volatile phenols (syringol and 4-allyl-syringol), propanoic acid, 4-hydroxy-2-butenolactone and vanillin. Acknowledgements The authors thank Madalena Miguel for technical assistance, Sun Baoshan and Marlene Vaz for manuscript revision and PAMAF-IED-2052 for the financial support. References Abbott, N., Puech, J.-L., Bayonove, C., & Baumes, R. (1995). Determination of the aroma threshold of cis and trans racemic forms of b-methyl-c-octalactone by gas chromatography-sniffing analysis. American Journal of Enology and Viticulture, 46(3), 292–294. Alford, E. D., & Leffingwell. J. C. (1998). GC/MS of liquid ‘‘hardwood smoke’’ extract. Available from http://www.leffingwell.com/ smoke1.htm. Artajona, J. (1991). Caracterisation del roble según su origen y grado de tostado, mediante la utilizacion de GC y HPLC. Viticultura/ Enologia Profesionalm, 14(5/6), 61–72. Belchior, A. P., Caldeira, I., Tralhão, G., Costa, S., Lopes, C., & Carvalho, E. (1998). Incidência da origem e queima da madeira de carvalho (Q. pyrenaica, Q. robur, Q. sessiflora, Q. alba/Q. stellata + Q. lyrata/Q. bicolor) e de castanho (C. sativa) em características fisico-químicas e organolépticas de aguardentes Lourinhã em envelhecimento. Ciência e Técnica Vitivinícola, 13(1–2), 107–118. Boidron, J. N., Chatonnet, P., & Pons, M. (1988). Influence du bois sur certaines substances odorantes des vins. Connaissance de la Vigne et du Vin, 22(4), 275–294. Borralho, A. C. R. (1994). Estudo de substâncias provenientes da madeira no envelhecimento de vinhos tintos. Suas incidências na qualidade. (pp. 27–35). Relatório final do curso de Engenharia Agro-Industrial, Universidade Técnica de Lisboa, Lisboa. Brenna, E., Fuganti, C., & Serra, S. (2003). Enantioselective perception of chiral odorants. Tetrahedron: Asymmetry, 14, 1–42. Caldeira, I. (2004). O aroma de aguardentes vínicas envelhecidas em madeira. Importância da tecnologia de tanoaria. (pp. 65–94). Dissertação para obtenção do grau de doutor em Engenharia Agro-Industrial, Instituto Superior de Agronomia–Universidade Técnica de Lisboa, Lisboa. Caldeira, I., Belchior, A. P., Clímaco, M. C., & Bruno de Sousa, R. (2002). Aroma profile of portuguese brandies aged in chestnut and oak woods. Analytica Chimica Acta, 458, 55–62. Caldeira, I., Canas, S., Costa, S., Lopes, C., Carvalho, E., & Belchior, A. P. (1998). Influence de lÕorigine du bois et de la technologie de fabrication des fûts sur la qualité des eaux-de-vie Lourinhã pendant
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