Univ. Bordeaux, Unité de recherche Œnologie, EA 4577, USC 1366 INRA, ISVV , 33882 Villenave d'Ornon cedex , France.
Univ. Bordeaux, CNRS, Bordeaux INP, ISM, UMR 5255 , 33400 Talence , France.
J Agric Food Chem. 2019 Sep 11;67(36):10137-10144. doi: 10.1021/acs.jafc.9b03185. Epub 2019 Aug 29.
Volatile extractive compounds from high-quality oak wood ( sp.) are responsible for important pleasant olfactory notes, such as coconut, wood, vanilla, caramel, and spice. Recently, a new off-flavor reminiscent of rancid butter has been detected in oak wood. Using gas chromatography-olfactometry (GC-O) coupled to several detection modes, such as nitrogen-phosphorus detection (GC-O-NPD) or mass spectrometry (GC-O-MS) and multidimensional GC-O coupled to time-of-flight mass spectrometry, six compounds containing nitrogen atoms were identified. The volatiles were suggested to belong to 2,5-disubstituted pyrazines family, which was confirmed by comparison with synthetic reference compounds. For this purpose, symmetric and dissymmetric 2,5-dialkylpyrazines were prepared from methyl esters of corresponding aliphatic amino acids (Val, Leu, and Ile) by a three-step, one-pot reaction under mild reducing conditions. Organoleptic descriptors and odor detection thresholds were also determined, whereas a bacterial origin explaining these off-flavors was hypothesized.
高质量橡木（sp.）中的挥发性萃取物化合物是重要的宜人嗅觉成分的来源，如椰子、木材、香草、焦糖和香料。最近，橡木中检测到一种新的异味，让人联想到腐臭的黄油。使用气相色谱-嗅觉测定法（GC-O）结合多种检测模式，如氮磷检测（GC-O-NPD）或质谱（GC-O-MS）和多维 GC-O 结合飞行时间质谱，鉴定出六种含氮化合物。这些挥发性物质被认为属于 2,5-取代的吡嗪家族，这通过与合成参考化合物的比较得到了证实。为此，通过温和还原条件下三步一锅法，从相应的脂肪族氨基酸（缬氨酸、亮氨酸和异亮氨酸）的甲酯制备对称和非对称 2,5-二烷基吡嗪。还确定了感官描述符和气味检测阈值，而假设了一种细菌来源来解释这些异味。
