Which aspect of beer tasting is primarily affected by the cleanliness of the glass?

The cleanliness of the glass has a significant impact on the aroma of the beer. When the glass is not properly cleaned, residues from previous beverages or contaminants can interfere with the beer's scent, which is a critical element of its overall flavor profile. Aroma is largely responsible for how we perceive flavors, as a significant amount of taste is derived from our sense of smell.

If the glass is dirty, it can mask the delicate aromas that the brewer intended to showcase, preventing the taster from fully experiencing the complexity of the beer. A clean glass ensures that these aromas are not altered by foreign residues, allowing for a more accurate and enjoyable tasting experience.