Chair of Food Chemistry and Molecular Sensory Science, Technische Universität München, Lise-Meitner-Str. 34, Freising D-85354, Germany.
J Agric Food Chem. 2021 Dec 22;69(50):15334-15344. doi: 10.1021/acs.jafc.1c06163. Epub 2021 Dec 7.
A quantitative H NMR-based approach was established, which allowed the direct and noninvasive analysis of molecular interactions between key coffee odorants and high-molecular-weight (HMW) melanoidin polymers. A clear distinction between covalent and noncovalent interactions was achieved by monitoring the time dependency of odorant-polymer interactions, resulting in four scenarios: covalent, π-π, covalent and π-π-, as well as no interactions. Evaluation of temperature influence on e.g. 2-furfurylthiol (FFT), revealed an altered behavior with increased π-π stacking at lower temperatures and accelerated covalent interactions at higher temperatures. Human sensory experiments with HMW material and a coffee aroma reconstitution model showed a drastic reduction of "roasty/sulfury" aroma notes, as well as an increased "sweetish/caramel-like" flavor. The lack of interactions between the "sweetish/caramel" smelling 4-hydroxy-2,5-dimethyl-3(2)-furanone with the HMW melanoidins in combination with the high binding affinity of coffee thiols explains the sensory evaluation and is obviously the reason for the fast disappearance of the typical "roasty/sulfury" aroma impressions of a freshly prepared coffee brew.
建立了一种基于定量 1H NMR 的方法，该方法允许直接和非侵入式分析关键咖啡香气与高分子量（HMW）类黑素聚合物之间的分子相互作用。通过监测香气-聚合物相互作用的时间依赖性，实现了对共价和非共价相互作用的清晰区分，从而产生了四种情况：共价、π-π、共价和 π-π-以及没有相互作用。评估温度对例如 2-糠硫醇（FFT）的影响时，发现随着温度的降低，π-π 堆积增加，而随着温度的升高，共价相互作用加速。使用 HMW 材料和咖啡香气重建模型进行的人体感官实验表明，“烘烤/硫磺”香气特征明显减少，同时“甜/焦糖样”风味增加。“甜/焦糖”气味的 4-羟基-2,5-二甲基-3(2)-呋喃酮与 HMW 类黑素之间缺乏相互作用，以及咖啡硫醇的高结合亲和力解释了感官评估，显然是新鲜制备的咖啡中典型“烘烤/硫磺”香气特征迅速消失的原因。
