Olfactory Characterization of Typical Odorous Pollutants Part I: Relationship Between the Hedonic Tone and Odor Concentration

Abstract

The hedonic tone is a suitable evaluation index which can truly reflect the psychological impact of an odor. To find out the relationship between the odor concentration (OC) and hedonic tone (H), dimethyl disulfide, limonene and butyl acetate were presented as typical odorants with different characters. A panel of 16 persons was engaged to rate the hedonic tone of a series sample with various concentrations according to the nine-point scale. The relationship between the hedonic tone and OC was established based on a multivariate logistic regression analysis. The research results demonstrated that the smell of dimethyl disulfide is unpleasant at various concentration levels, and its perceived unpleasantness is increased with OC, and at the critical point (H = −0.5), the odor index of dimethyl disulfide is 0.5 (OC = 3 OUE·m−3). For limonene, its smell is pleasant when the odor index is between 1.4 and 3.3 (OC = 25~1995 OUE·m−3). For butyl acetate, the average results showed an unpleasant character with the corresponding odor index of 1.87 (OC = 74 OUE·m−3). Each odorant has a unique hedonic behavior curve from which the annoyance potential of different odorants can be clearly discriminated, with the order of dimethyl disulfide > butyl acetate > limonene. The regression equations showed a quadratic nonlinear function between the hedonic tone and OC.