Temperature Effects on Drinking Water Odor Perception
Thirteen volunteer panelists were trained according to Standard Method 2170, flavor profile analysis (FPA). Following training these panelists underwent triangle test screening to determine whether or not they could detect the odorants used in this study. Following triangle testing, panelists underwent directional difference testing to determine if temperature affected odor perception when presented with two water samples. Following directional difference testing, panelists used FPA and evaluated water samples that contained odorants at either 25°C or 45°C. Samples containing geosmin cooled to 5°C were also evaluated.
Sensory analyses experiments indicate that odor intensity is a function of both aqueous concentration and water temperature for geosmin, MIB, nonadienal, n-hexanal, free chlorine, and 1-butanol. The higher water temperature resulted in an increase in odor intensity for some, but not all, concentrations of geosmin, 2-methylisoborneol, trans-2, cis-6-nonadienal, n-hexanal, free chlorine, and 1-butanol. Additionally, above 400 ng/L of geosmin, 400 ng/L of MIB, and 100 ng/L the odor intensity was equal to or less than the odor intensity at 600, 600, and 200 ng/L, respectively. Henry's Law should predict that an increase in concentration would increase the amount of odorant the panelist comes into contact with; however, results demonstrated that at specific aqueous odorant concentrations odor perception did not follow Henry's Law. Odor response to drinking water containing isobutanal was affected by concentration but not water temperature.