Developing hexanal as an odor reference standard for sensory analysis of drinking water

There are many analytical and sensory methods to analyze drinking water for flavor and off-flavors before it reaches consumers. Flavor profile analysis (FPA) is one of the most comprehensive methods. A well-trained panel is essential for FPA and although taste standards are well established, FPA training lacks an odor reference standard. In search of an odor reference standard, four different panel groups were trained and tested for n-hexanal at various concentrations (1–1000 μg/L) over 14 months. The Weber–Fechner plots for n-hexanal showed a linear and overlapping relationship for all panels. Analytical measurements demonstrated that the headspace concentration of n-hexanal was constant after 5 sniffs at 45 °C and it remained constant during FPA sessions for up to 4 h. The panelists liked the grassy odor of n-hexanal, which did not result in fatigue, and testing demonstrated that approximately 95% of the population can detect n-hexanal's odor. n-Hexanal is proposed as an odor reference standard for FPA training to define odor intensities because it is chemically stable, follows Weber–Fechner law, mimics grassy odors found in drinking water, and was acceptable to the human panelists.