What does wild yeast refer to in brewing?

Wild yeast in brewing refers to a variety of yeast strains that are not cultivated or controlled, which can contribute complex flavors and aromas to fermented beverages. The correct choice identifies wild yeast as encompassing varieties of Brettanomyces, which is known for producing distinctive, earthy, and funky characteristics often desired in certain styles of beer and cider, as well as non-brewing yeast strains that can be present in the environment.

The significance of incorporating wild yeast lies in its ability to induce spontaneous fermentation, particularly in styles like lambics or farmhouse ales. In these cases, brewers often leverage microorganisms from the environment, which can lead to a wide range of unique characteristics that differ from the predictability of cultivated yeast strains.

In contrast, the other options are too narrow and do not encompass the broad definition of wild yeast. They limit wild yeast to either specific strains, such as only Brettanomyces or only those cultivated for cider, which doesn't reflect the broader range of yeast types found in various fermentation environments. Additionally, describing wild yeast as a type of commercially cultivated yeast fails to recognize that wild yeast, by definition, should be natural and uncontrolled rather than domesticated for brewing purposes.