Which two mouthfeel sensations are generally considered undesirable in coffee?

Astringency and metallic sensations are typically undesirable in coffee for several reasons. Astringency can create a dry, puckering sensation in the mouth, which most consumers find unpleasant, as it detracts from the overall enjoyment of the beverage. This can occur due to excessive extraction of tannins or compounds that lead to this dry feeling, making the coffee feel harsh rather than smooth and balanced.

The metallic sensation can arise from various sources, such as the brewing process, the water used, or the equipment itself. This taste disrupts the clean, pleasant flavors one would expect from a good cup of coffee. It can overpower the more delicate flavors and nuances, resulting in an unpleasant drinking experience.

In contrast, thickness and sweetness, bitterness and sourness, or oiliness and sweetness could be acceptable or even desirable depending on the coffee variety and personal taste preferences. For instance, some coffee aficionados enjoy a certain level of bitterness or sourness as part of complex flavor profiles, and some coffee beans can have a natural oiliness that contributes positively to the mouthfeel.