Smoky, vanilla or clove-like? Structure-Odor Activity Relationships of Guaiacol Derivatives

Smoky smells, primarily comprising guaiacols, phenols, and cresols, are enjoyed in diverse foods and beverages, such as whiskey, smoked ham, cheese, or baked goods, such as pizza. They contribute to the flavor and smell experience when smoking tobacco products or when sitting at a fireplace. In other cases, smoky smells indicate potential locations of pyrolytic and combustion processes and may act as alarm signals. In the animal kingdom, interestingly, some compounds related to common constituents of smoke may serve as chemo-communication tools or even pheromones. However, previous studies on the odor properties of alkylated and halogenated guaiacols, phenols, and cresols demonstrate that smoky smell is not the same for everybody. When resolving the underlying chemical structures and carrying out systematic structure-odor activity relationship investigations, one realizes that there are obviously more complicated considerations for each of us in the smell of smoke. This chapter gives an overview of the sensory data of guaiacol and selected structurally related odorants, such as alkylated, alkenylated, methoxylated, and halogenated guaiacol derivatives.