The attribute rating test for sensory analysis.
This new sensory method evaluates the intensity of an odorant by using a modified "paired-comparison" format. It can be applied to any situation for which the odor-causing agent is known and a purified standard is available. The attribute rating test requires that a standard solution of the odorant be prepared at a concentration that is both readily recognized by most individuals and likely to evoke customer complaints. Within an hour individuals can be trained to compare the odor type and intensity of the standard to water samples, then rate the odor in the sample as "not detected," "less than the standard," "equal to standard," or "greater than the standard." The attribute rating test was successfully used by a full-scale water treatment facility to monitor the intensity of geosmin in the source water and to determine the effectiveness of powdered activated carbon for controlling its earthy-odor in treated water.