Negative description (also called phenolic) for the smell and taste, especially of white wines in the context of a wine appeal, where this is generally undesirable compared to red wines. Although these contain much less phenols than red wines, they are much more susceptible to errors due to excessive phenol content. Causes of phenol-rich grape material are strong sun exposure (which is intensified by strong defoliation) and drought stress. Such wines have a rough, bitter and overly astringent taste. However, phenol clay is also used as an alternative term for horse sweat, which, when strongly expressed, means a wine defect (phenol defect). As measures against excessive phenol content in wine, various substances such as gelatine, albumin, casein or PVPP are added to the grape must and/or wine.