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

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4-allyl-syringol were also identified for the first time. Some authors reported the presence of other phenols, namely phenol, o-cresol, p-cresol, m-cresol, 4-ethylphenol and methyleugenol (Chatonnet et al., 1989; Nabeta et al., 1986; Nishimura et al., 1983) but these compounds were not found in our wood extracts. 3.2. Effect of wood origin The cooperage industry needs to have criteria for the control of raw material. Thus, we decided first to compare the 14 unheated wood samples (7 woods · 2 replicates), in order to evaluate the possibility of discriminating the different types of wood based on the levels of volatile compounds, and after that, we compare all the wood samples in order to evaluate if the wood discriminating pattern is influenced by the toasting process. I. Caldeira et al. / Journal of Food Engineering 76 (2006) 202–211 205 Table 1 includes the quantitative analysis of several volatile compounds in the unheated woods and the ANOVA results, whereas Table 2 presents the results from the analysis of all the different types of wood (unheated and heated woods). The high standard deviation indicates the strong variability of the contents of these compounds in the different types of wood, which is in agreement with the results of other authors (Canas et al., 2000; Chatonnet & Dubourdieu, 1998; Masson et al., 1995; Mosedale & Savill, 1996; Simon, Conde, Cadahia, & Garcia-Vallejo, 1996). The ANOVA showed (Table 1) that wood origin had a very highly significant effect on the quantity of cis-bmethyl-c-octalactone and eugenol, a highly significant effect in the levels of acetic acid, furfural, 4-hydroxy-2butenoic acid lactone, hexanoic acid, trans-b-methyl-coctalactone and vanillin, and a significant effect on the levels of guaiacol. Table 1 Contents of volatile compounds in aqueous alcoholic unheated wood extracts and wood origin effect (results expressed as lg per g of dry wood) Wood origin effect CNE CNF CNG CAST CFA CFL CAM Acetic acid ** x 12.22a 67.97d 50.65c 19.09ab 70.20d 13.67a 34.74bc SD 5.16 0.58 9.61 11.19 6.87 0.54 5.29 Furfural ** x 1.94a 12.51b 4.64a 2.27a 13.63b 4.51a 9.78b SD 0.67 3.27 0.06 0.81 3.32 1.47 0.28 5-Methyl-furfural n.s. x 0.00 0.28 0.00 0.25 0.77 0.28 0.63 SD 0.00 0.40 0.00 0.35 0.19 0.40 0.31 4-Hydroxy-2-butenoic acid lactone ** x 0.00a 1.27b 0.00a 0.27a 1.50b 0.00a 1.26b SD 0.00 0.48 0.00 0.39 0.35 0.00 0.43 HMF n.s. x 1.67 2.40 2.70 0.91 0.98 0.26 0.84 SD 1.29 0.43 0.07 0.14 1.38 0.37 0.05 Propanoic acid n.s. x 0.00 0.82 0.36 0.21 0.89 0.00 0.36 SD 0.00 0.04 0.50 0.30 0.40 0.00 0.51 Hexanoic acid ** x 0.64a 8.35b 1.47a 1.16a 8.76b 1.06a 12.52b SD 0.00 4.27 0.06 0.71 2.21 0.01 2.27 trans-b-Methyl-c-octalactone ** x 2.31bc 2.68bc 2.47bc 0.23a 1.93b 2.87c 2.73bc SD 0.23 0.79 0.24 0.33 0.06 0.35 0.21 cis-b-Methyl-c-octalactone *** x 6.72a 7.15a 5.30a 0.34a 4.93a 7.18a 35.40b SD 3.79 3.00 0.67 0.48 0.30 1.39 6.44 Octanoic acid n.s. x 0.75 3.24 2.15 1.41 5.64 1.04 3.92 SD 0.16 2.40 0.74 1.21 1.88 0.09 1.69 Decanoic acid n.s. x 1.60 0.51 2.40 1.42 1.55 1.51 0.87 SD 0.22 0.72 1.70 0.45 0.08 0.78 0.02 Dodecanoic acid n.s. x 2.03 1.56 3.82 0.88 1.01 3.86 1.92 SD 0.01 0.05 2.21 1.24 1.42 0.13 0.50 Guaiacol * x 0.42a 1.25b 0.32a 0.38a 1.19b 0.09a 1.48b SD 0.25 0.45 0.45 0.26 0.35 0.13 0.02 Eugenol *** x 0.94a 2.69b 1.08a 0.71a 1.17a 1.01a 4.48c SD 0.02 0.52 0.48 0.06 0.15 0.11 0.33 Syringol n.s. x 0.39 0.36 0.00 0.53 0.36 0.00 0.00 SD 0.56 0.51 0.00 0.21 0.51 0.00 0.00 4-Allyl-syringol n.s. x 1.07 0.45 1.40 1.53 0.33 0.66 2.00 SD 0.64 0.63 0.60 0.06 0.47 0.93 1.12 Vanillin ** x 4.78bc 4.78bc 5.50c 2.90ab 8.32d 1.21a 5.78c SD 1.32 0.10 0.56 1.25 0.89 0.29 0.06 Acetovanillone n.s. x 1.89 0.00 0.00 1.28 0.44 0.00 0.91 SD 1.24 0.00 0.00 1.81 0.63 0.00 0.13 x, means of two 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.
206 I. Caldeira et al. / Journal of Food Engineering 76 (2006) 202–211 Table 2 Contents of volatile compounds in aqueous alcoholic wood extracts (unheated and heated woods) and wood origin effect (results expressed as lg per g of dry wood) Compound Wood origin effect CNE CNF CNG CAST CFA CFL CAM Acetic acid ** x 31.23a 63.46cd 77.26d 34.33a 52.16bc 45.67ab 42.51ab SD 13.55 23.76 22.73 16.79 15.63 21.09 22.17 Furfural n.s. x 105.53 78.99 138.33 86.38 92.85 83.58 92.85 SD 157.07 56.70 140.92 113.73 50.96 45.81 80.32 5-Methyl-furfural n.s. x 10.40 9.63 16.80 11.04 10.70 14.14 15.39 SD 17.03 9.87 20.64 13.63 8.14 8.67 15.38 4-Hydroxy-2-butenoic acid lactone ** x 0.59a 1.05ab 1.84c 1.37bc 1.48bc 1.53bc 1.61c SD 1.03 0.57 1.43 1.02 0.34 1.22 0.86 HMF ** x 13.15a 23.53bc 26.42c 16.60ab 13.22a 23.06bc 13.63a SD 14.92 23.90 26.26 16.03 12.31 21.15 14.09 Propanoic acid * x 0.37a 0.44a 0.99b 0.40a 0.53a 0.67ab 0.57a SD 0.63 0.39 0.58 0.33 0.40 0.54 0.53 Hexanoic acid ** x 1.21a 4.13b 3.43b 3.75b 4.95bc 1.55a 6.43c SD 0.40 3.28 2.50 2.21 3.16 0.75 4.99 trans-b-Methyl-c-octalactone ** x 3.07bc 2.95bc 3.10bc 0.66a 1.60ab 5.63d 4.26cd SD 0.88 0.94 1.93 0.31 0.95 3.07 1.04 cis-b-Methyl-c-octalactone + 4-methyl-guaiacol ** x 9.15bc 11.24c 8.80bc 0.88a 4.50ab 17.99d 46.59e SD 4.54 6.93 4.71 0.72 2.38 13.06 9.43 Octanoic acid n.s. x 2.02 2.53 2.10 2.61 2.87 1.77 2.48 SD 1.83 2.49 0.81 1.24 2.07 1.14 1.47 Decanoic acid n.s. x 2.31 2.19 1.31 1.26 1.13 2.17 1.02 SD 0.80 3.39 1.00 0.40 0.49 1.06 0.31 Dodecanoic acid n.s. x 3.01 3.82 2.26 1.60 1.64 3.34 3.77 SD 2.12 4.56 1.34 0.77 1.10 1.81 2.13 Guaiacol ** x 1.59c 0.77a 1.00ab 0.93ab 1.07abc 0.62a 1.43bc SD 0.25 0.45 0.45 0.26 0.35 0.13 0.02 Eugenol ** x 1.74ab 2.82d 1.86abc 2.11bcd 1.22a 2.65cd 4.55d SD 0.86 1.34 1.11 1.14 0.36 1.73 0.47 Syringol n.s. x 0.86 1.38 1.37 0.91 0.79 2.05 1.44 SD 1.81 2.11 2.47 0.91 1.02 2.21 2.42 4-Allyl-syringol n.s. x 1.30 2.13 1.85 2.72 2.87 2.99 3.26 SD 1.25 1.61 1.79 1.09 4.34 2.13 1.67 Vanillin ** x 15.10a 18.86ab 21.13ab 24.70bc 24.17b 32.82c 22.56ab SD 11.62 15.38 16.95 20.34 18.17 26.91 18.92 Acetovanillone * x 0.47a 1.93abc 1.59ab 2.60bc 1.60ab 3.63c 1.37ab SD 1.05 4.02 2.56 2.01 1.25 2.71 1.08 x, means of eight 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. When the analysis was performed with all the different types of wood samples (Table 2) it was detected a wood origin effect on the same variables, namely acetic acid, 4-hydroxy-2-butenoic acid lactone, hexanoic acid, trans-b-methyl-c-octalactone, cis-b-methyl-c-octalactone + 4-methyl-guaiacol, guaiacol, eugenol, and vanillin with exception for the furfural, HMF, propanoic acid and acetovanillone levels. However the results of unheated wood discrimination, based on the majority of analysed compounds, were quite different from those obtained with all the different types of wood. Only for the amounts of hexanoic acid, trans-b-methylc-octalactone, cis-b-methyl-c-octalactone and eugenol, the wood discrimination was similar on both analyses. The two isomers of b-methyl-c-octalactone, which have high sensory impact (Abbott, Puech, Bayonove, & Baumes, 1995; Boidron, Chatonnet, & Pons, 1988), allow to distinguish between French and American oak extracts and their related aged beverages (Guichard, Fournier, Masson, & Puech, 1995; Guymon & Crowell, 1972; Onishi, Guymon, & Crowell, 1977). In this work, we found a significant effect of wood origin on trans and cis isomer amounts in unheated woods (Table 1). Concerning the Portuguese chestnut wood, it is remarkable that it has a significant low level of these two isomers. In fact, in a previous work on the chestnut volatile evaluation, the b-methyl-c-octalactone isomers were not found (Clímaco & Borralho, 1996). On the contrary to other results (Masson et al., 1995; Mosedale & Savill, 1996) we found that CFL wood has higher amount of trans isomer than CFA wood (Tables 1 and 2). It was verified that cis-b-methyl-c-octalactone contents, permits the formation of two groups, one constituted by the CAM with the highest amounts of this compound, and another with all the other types of wood. These results are in agreement with other authors
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