Wild yeast cultivation — capturing and concentrating the wild Saccharomyces and non-Saccharomyces yeasts from fruit skins, grains, and the environment — is the foundation of natural wine production, sourdough bread, and traditional fermented beverage production. The Noma Guide's documentation of wild yeast cultivation provides practical parameters for home fermenters seeking to work with local yeast populations.
- **The substrate selection:** Fruit skins carry the highest wild yeast populations — unwashed organic fruit is the richest source. Grapes, plums, and apples consistently carry productive wild yeast populations. - **The capture medium:** A sugar-water solution (5–10% sugar) in which the fruit skin/whole fruit is suspended — the wild yeasts proliferate in this environment over 24–48 hours, producing visible CO₂ bubbling. - **Temperature:** 22–28°C — the optimal range for wild yeast proliferation. - **Selecting for specific organisms:** Wild yeast populations are diverse — some produce off-flavours (ethyl acetate from excess Kloeckera apiculata activity produces a nail polish note). The first 24 hours of fermentation tend to be dominated by apiculate yeasts; Saccharomyces cerevisiae (the wine/bread yeast) typically dominates after the first 24 hours as the alcohol concentration inhibits the less alcohol-tolerant species. - **The starter:** The captured wild yeast culture is used to inoculate bread dough, fermented beverages, or other fermentation substrates.
Noma Fermentation