Cheon Eunjin, Mattes Richard D
Department of Nutrition Science, Purdue University, 812 W State Street, West Lafayette, IN 47907-2059, USA.
Chem Senses. 2021 Jan 1;46. doi: 10.1093/chemse/bjab023.
Nonesterified fatty acids (NEFA) are effective taste stimuli. The quality they impart has not been well characterized. Sourness, and "fattiness" have been reported, but an irritation component has also been described and how these transition with gradations of aliphatic chain length has not been systematically studied. This study examined intensity and quality ratings of NEFA ranging from C2 to C18. Oral sites and the time course of sensations were also monitored. Given all NEFA contain carboxylic acid moieties capable of donating hydrogen ions, the primary stimulus for sour taste, testing was conducted with and without sour adaptation to explore the contribution of sour taste across the range of NEFA. Short-chain NEFA (C2-C6) were rated as predominantly sour, and this was diminished in C2 and C4 by sour adaptation. Medium-chain NEFA (C8-C12) were rated as mainly irritating with long-chain NEFA (C18) described mostly as bitter. The latter may reflect the lack of "fatty" lexicon to describe the sensation. Short-chain NEFA were mostly localized to the anterior tongue and were of rapid onset. The sensation from medium-chain NEFA was attributed to the lateral tongue, whereas medium- and long-chain NEFA sensations were predominantly localized to the back of the tongue and throat and had a longer lag time. The findings indicate there is a systematic transition of NEFA taste quality and irritation with increments in chain length and this is consistent with multiple modes of transduction.
非酯化脂肪酸（NEFA）是有效的味觉刺激物。它们所赋予的味觉特性尚未得到充分描述。据报道有酸味和“油腻感”，但也有人描述了一种刺激成分，并且这些特性如何随脂肪链长度的变化而转变尚未得到系统研究。本研究考察了碳链长度从C2到C18的NEFA的强度和味觉评级。还监测了口腔部位和感觉的时间进程。鉴于所有NEFA都含有能够提供氢离子的羧酸部分，而氢离子是酸味的主要刺激因素，因此在有和没有酸味适应的情况下进行了测试，以探究酸味在整个NEFA范围内的作用。短链NEFA（C2 - C6）的评级主要为酸味，并且在C2和C4中，酸味适应使其酸味减弱。中链NEFA（C8 - C12）的评级主要为刺激性，而长链NEFA（C18）大多被描述为苦味。后者可能反映了缺乏描述这种感觉的“油腻”词汇。短链NEFA大多集中在前舌，且起效迅速。中链NEFA的感觉归因于舌侧，而中链和长链NEFA的感觉主要集中在舌后部和喉咙，且延迟时间更长。研究结果表明，随着链长增加，NEFA的味觉质量和刺激存在系统性转变，这与多种转导模式一致。
