Qualitative and Quantitative Sex-Related Differences in the Perception of Single Molecules from Coffee Headspace

Abstract

One of the still-debated topics regarding the olfactory function concerns the presence or absence of sex-related differences in individuals. In this study, we checked for a relationship between the olfactory function of females and males and their ability to perceive single molecules, and researched how this can influence the intensity with which the complex odor formed by a set of single molecules is perceived. First, females and males were classified as normosmic or hyposmic based on the TDI olfactory score obtained using the Sniffin' Sticks test. Subsequently, the headspace of roasted coffee beans, as a complex olfactory stimulus, was broken down into single molecules by means of a chromatographic column; these were simultaneously conveyed to a mass spectrometer (for their subsequent classification) and to the human nose, which acts as a chemical sensor by means of an olfactometer port. The results obtained with this gas chromatography-olfactometry approach show both qualitative and quantitative differences between females and males, with females performing better than males. In addition, the odor intensity reported by females when sniffing pen #10, containing coffee aroma, is significantly higher than that reported by males. In conclusion, these data highlight that the human ability to perceive both single compounds and complex odors is strongly conditioned, not only by the olfactory function of individuals, but also by their sex.

Keywords: GC-O technique; VARUs intensity; gender; individual variability; smell.

Figure 1

Effect of the TDI olfactory status on the ability to perceive single molecules. (A) Mean values ± SE of the number of total- and coffee-molecules smelled during the GC-O experiments by subjects, according to their TDI olfactory status. * Indicates significant differences between individuals with normosmia or hyposmia (p < 0.0001; Fisher’s LSD test subsequent to one-way ANOVA). (B) Mean values ± SE of the number of total- and coffee-molecules smelled during the GC-O experiments by females and males, according to their TDI olfactory status. Different letters indicate significant differences between individuals with normosmia or hyposmia (females: a-a_i; males: b-b_i; p < 0.01; Fisher’s LSD test subsequent to one-way ANOVA). * Indicates significant differences between females and males within the same TDI olfactory status (p ≤ 0.012; Fisher’s LSD test subsequent to one-way ANOVA).

Figure 2

Relationship between TDI olfactory score and ability to perceive single molecules. Correlation analyses between TDI olfactory score and the number of total- and coffee-molecules smelled by subjects of both sexes together (A), only females (B) or only males (C).

Figure 3

Relationship between effect of the TDI olfactory status on the intensity perceived for coffee-odor pen. (A) Mean values ± SE of the intensity perceived for coffee-odor pen by subjects according to their TDI olfactory status. * Indicates significant differences between individuals with normosmia or hyposmia (p = 0.0002; Fisher’s LSD test subsequent to one-way ANOVA). (B) Mean values ± SE of the intensity perceived for coffee-odor pen by each female and male separately, according to their TDI olfactory status. Different letters indicate significant differences between individuals with normosmia or hyposmia (females: a-a_i; males: b-b_i; p < 0.01; Fisher’s LSD test subsequent to one-way ANOVA). * Indicates significant differences between females and males within the same TDI olfactory status (p ≤ 0.027; Fisher’s LSD test subsequent to one-way ANOVA).

Figure 4

Relationship between TDI olfactory status and intensity perceived for coffee-odor pen. Correlation analyses between the intensity perceived for coffee-odor pen by each female (A) and male (B).

Figure 5

Relationship between the intensity perceived for coffee-odor pen and number of single molecules. Correlation analyses between the number of total- and coffee-molecules smelled and the intensity perceived for the coffee-odor pen by each female (A) and male (B).