Which phenomenon can affect wine quality due to grape spoilage?

Botrytis cinerea is a specific type of fungus commonly known as noble rot. This phenomenon can significantly affect the quality of wine, particularly in the production of sweet wines. Under certain conditions, this fungus can result in a desirable concentration of sugars and flavors in the grapes, ideal for producing high-quality dessert wines, such as Sauternes or Tokaji. However, if the conditions are not right, it can lead to spoilage, resulting in unpleasant and undesirable flavors in the wine.

In contrast, ozone depletion, terroir, and photochemical smog do not directly influence grape spoilage in the same manner. Ozone depletion relates more to environmental issues rather than specific impacts on grape quality. Terroir is the composite of factors including soil, climate, and geography that influence the taste and character of wine, but it doesn't inherently cause spoilage. Photochemical smog impacts air quality and can negatively affect agriculture, but the direct correlation to spoilage in grapes is not as clear as with Botrytis cinerea. Thus, the impact of Botrytis cinerea on grape spoilage is a critical factor in understanding wine quality.