Department of Public Health, California State University, Fresno, CA 93740-8031, USA.
Int J Environ Res Public Health. 2022 Dec 15;19(24):16829. doi: 10.3390/ijerph192416829.
Characterization of taste- and flavor-producing metals, namely iron and copper, in drinking water is a multifaceted subject. Both metals are essential nutrients, can be toxic, and are known to produce unpleasant tastes and flavor sensations in drinking water. Ingestion of trace metal contaminants through drinking water is a probable source of human exposure. Biochemical mechanisms of metallic flavor perception have been previously described; however, less is known about how variations in salivary constituents might impact individuals' sensitivities to metallic flavors and beverage consumption behaviors. This research presents findings from in vitro experiments, using artificial human saliva, to better understand the role of salivary lipids and proteins on metallic flavor production as measured by biomarkers of metal-induced oxidative stress. The results indicate that metal-induced lipid oxidation, as measured by thiobarbituric acid reactive substances (TBARS), is dominated by salivary proteins, is slightly inhibited in the presence of salivary nitrite, and is detectable by the TBARS method at and above respective concentrations of 9 µM (0.5 mg/L) and 90 µM (5 mg/L), which are both above the aesthetic standards for iron (0.3 mg/L) and copper (1.0 mg/L) in drinking water. Preliminary study with human subjects indicated that reduction in metallic flavor sensitivity, as measured by the best estimate flavor threshold for ferrous iron among 33 healthy adults aged 19-84 years old (22 females), corresponded with reduced drinking water consumption and increased caloric beverage intake among older subjects (>60 years), as determined by a validated self-reported beverage intake questionnaire. These findings provide insights for further research to examine how salivary constituents can impact humans' sensory abilities in detecting metallic off-flavors in water, and how reduced metallic flavor sensitivity may influence beverage choices and drinking water consumption.
水中味觉和风味产生金属（即铁和铜）的特性是一个多方面的课题。这两种金属都是必需的营养物质，但也可能有毒，已知它们会使饮用水产生不愉快的味道和风味。通过饮用水摄入痕量金属污染物是人类暴露的一个可能来源。金属风味感知的生化机制以前已经有过描述；然而，对于唾液成分的变化如何影响个体对金属风味的敏感性以及饮料消费行为，人们知之甚少。本研究通过使用人工唾液的体外实验，提供了一些发现，以更好地了解唾液脂质和蛋白质在金属风味产生中的作用，金属风味产生由金属诱导的氧化应激生物标志物来衡量。研究结果表明，金属诱导的脂质氧化（通过硫代巴比妥酸反应物质 (TBARS) 来衡量）主要由唾液蛋白质主导，在存在唾液亚硝酸盐的情况下略有抑制，并且在各自浓度为 9 µM（0.5mg/L）和 90 µM（5mg/L）以上时，TBARS 方法可检测到，这两个浓度均高于饮用水中铁（0.3mg/L）和铜（1.0mg/L）的美学标准。对 33 名年龄在 19 至 84 岁之间（22 名女性）的健康成年人进行的初步研究表明，铁的最佳估计风味阈值（二价铁）的金属风味敏感性降低与老年人（>60 岁）的饮用水摄入量减少和高卡路里饮料摄入量增加相对应，这是通过经过验证的自我报告饮料摄入量问卷确定的。这些发现为进一步研究提供了思路，以检验唾液成分如何影响人类在水中检测金属异味的感官能力，以及金属风味敏感性降低如何影响饮料选择和饮用水消费。
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