涩味是最复杂的口腔感觉之一。当饮用葡萄酒、茶或其他含有多酚的食物时,会出现这种干燥、起皱的口感。这种干燥口感背后的确切机制尚不完全清楚。在这里,我们描述了一种系统的摩擦学方法来测量模型和真实唾液,以了解唾液蛋白(粘蛋白和富含脯氨酸的蛋白质 (PRP))对基于润滑的涩味的具体作用。我们的方法表明,润滑损失有两种途径,部分涉及反应性顺序很重要的不可逆分子机制。对于人类唾液,我们发现了两种润滑机制:(I) 使用酚类化合物,我们发现由于氢键形成而导致聚集引起的润滑损失,这主要取决于苯酚的大小:大的多酚允许聚集引起的润滑损失,但小酚不会。(II) 对于与唾液结合的金属盐,我们观察到由于静电相互作用而没有润滑损失的聚集。我们发现润滑损失是由唾液 PRP 层的特定去除引起的,而 PRP 存在下的粘蛋白聚集不会导致润滑损失。此外,我们表明添加能够减少蛋白质-多酚氢键的溶剂(例如乙醇)可以防止润滑损失。还可以通过添加可提供粘性润滑的高粘性流体(甘油)来补偿润滑损失。我们观察到由于静电相互作用而没有润滑损失的聚集。我们发现润滑损失是由唾液 PRP 层的特定去除引起的,而 PRP 存在下的粘蛋白聚集不会导致润滑损失。此外,我们表明添加能够减少蛋白质-多酚氢键(例如乙醇)的溶剂可以防止润滑损失。还可以通过添加可提供粘性润滑的高粘性流体(甘油)来补偿润滑损失。我们观察到由于静电相互作用而没有润滑损失的聚集。我们发现润滑损失是由唾液 PRP 层的特定去除引起的,而 PRP 存在下的粘蛋白聚集不会导致润滑损失。此外,我们表明添加能够减少蛋白质-多酚氢键(例如乙醇)的溶剂可以防止润滑损失。还可以通过添加可提供粘性润滑的高粘性流体(甘油)来补偿润滑损失。我们表明添加能够减少蛋白质-多酚氢键的溶剂(例如乙醇)可以防止润滑损失。还可以通过添加可提供粘性润滑的高粘性流体(甘油)来补偿润滑损失。我们表明添加能够减少蛋白质-多酚氢键的溶剂(例如乙醇)可以防止润滑损失。还可以通过添加可提供粘性润滑的高粘性流体(甘油)来补偿润滑损失。
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A tribological approach to astringency perception and astringency prevention
Astringency is one of the most complex oral sensations. This dry, puckering mouthfeel occurs when consuming wine, tea, or other foods containing polyphenols. The exact mechanism behind this dry mouthfeel is not completely understood. Here, we describe a systematic tribological approach to measure model and real saliva to understand the specific role of the salivary proteins (mucins and proline-rich proteins (PRPs)) on lubrication-based astringency. Our approach reveals that there are two routes towards lubrication losses, partly involving irreversible molecular mechanisms for which the order of reactivity matters. For human saliva, we find two lubrication mechanisms: (I) Using phenolic compounds, we find aggregation-induced lubrication losses due to hydrogen bond formation, which depend critically on phenol size: large polyphenols allow for aggregation-induced lubrication losses, but small phenols do not. (II) For metal salts combined with saliva, we observe aggregation without lubrication losses as a result of electrostatic interactions. We find that lubrication losses are caused by the specific removal of the salivary PRP layer, whereas mucin aggregation in the presence of PRPs does not lead to lubrication losses. Additionally, we show that the addition of solvents that are able to reduce protein-polyphenol hydrogen bonding (e.g. ethanol) can prevent lubrication losses. Lubrication losses can also be compensated by the addition of highly viscous fluids (glycerol) that can provide viscous lubrication.