Chair of Aroma and Smell Research, Friedrich-Alexander-Universität Erlangen-Nürnberg, Department of Chemistry and Pharmacy, Henkestraße 9, 91054 Erlangen, Germany; Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Straße 35, 85354 Freising, Germany.
Fraunhofer Institute for Process Engineering and Packaging IVV, Giggenhauser Straße 35, 85354 Freising, Germany; Agricultural Biochemistry Department, Faculty of Agriculture, Ain Shams University, P.O. Box 68, Hadayek Shobra, 11241 Cairo, Egypt.
Food Res Int. 2021 Dec;150(Pt A):110776. doi: 10.1016/j.foodres.2021.110776. Epub 2021 Oct 21.
Oak wood contains aroma-active compounds that contribute significantly to the chemical structure, olfactory and gustatory qualities of alcoholic beverages and vinegars as by-products that have been either fermented and/or aged in oak barrels. The chemical composition of cooperage oak is highly variable, depending on the degree of toasting and natural seasoning. However, it is unclear whether the odor of oak varies according to different geographical regions and pedoclimatic conditions. Especially in view of the actual challenges in forestry in relation to climate change, the present study aimed at elucidating the odorous constituents of nine natural oak samples from Germany, Austria and Hungary with respect to these influencing parameters. The odor profiles of the oaks were compared, the potent odorants were determined, and selected odorants were quantified using stable isotope dilution assays (SIDA). The majority of the identified odorants in all samples were fatty acid degradation products, followed by a series of odorants with terpenoic structure and others resulting from the degradation of lignin. Several different odorants including 2-propenoic acid and cinnamaldehyde are reported here for the first time in oaks from different growth regions. Odor activity values (OAVs), calculated based on odor thresholds (OTs) in water, revealed hexanal, (E)-2-nonenal, (Z)-3-hexenal, eugenol, vanillin, and whiskey lactone as potent odorants for the oak odor. Principal component analysis of the data obtained from sensory evaluation, comparative aroma extract dilution analysis (cAEDA) and their corresponding quantified odorants showed that the highest separation rate was obtained for Hungarian oak, whereas Austrian and Bavarian oak samples were more similar. Recombination experiments by mixing the dominant odorants in their naturally occurring concentrations revealed a good agreement of the smell properties of the model mixture with the smell of the respective original sample. These findings aimat evaluating and establishing a better understanding of the distinctive smell of oak wood and demonstrated the prospects of new oak sources.
橡木含有香气活性化合物，这些化合物对酒精饮料和醋的化学结构、气味和味道有重要贡献，它们是在橡木桶中发酵和/或陈酿的副产品。制桶橡木的化学成分高度可变，取决于烘烤和自然陈化的程度。然而，橡木的气味是否因不同的地理区域和土壤气候条件而有所不同尚不清楚。特别是考虑到林业在气候变化方面面临的实际挑战，本研究旨在阐明来自德国、奥地利和匈牙利的 9 个天然橡木样本的气味成分及其受这些影响因素的影响。比较了橡木的气味特征，确定了强烈气味的物质，并使用稳定同位素稀释分析（SIDA）定量了选定的气味物质。在所有样品中，大多数鉴定出的气味物质都是脂肪酸降解产物，其次是一系列具有萜烯结构的气味物质和其他源自木质素降解的气味物质。在不同生长地区的橡木中，这里首次报道了包括 2-丙烯酸和肉桂醛在内的几种不同的气味物质。基于水中气味阈值（OT）计算的气味活性值（OAV）表明，己醛、（E）-2-壬烯醛、（Z）-3-己烯醛、丁香酚、香草醛和威士忌内酯是橡木气味的强烈气味物质。基于感官评价、比较香气萃取稀释分析（cAEDA）及其相应定量气味物质的数据的主成分分析表明，匈牙利橡木的分离率最高，而奥地利和巴伐利亚橡木样本更为相似。通过混合天然存在浓度的主导气味物质进行重组实验，表明模型混合物的气味特性与相应原始样本的气味特性吻合较好。这些发现旨在评估和建立对橡木独特气味的更好理解，并展示了新橡木来源的前景。
