Understanding Yeast Types
Different types of yeast have varying moisture contents and granule sizes, which means they cannot be substituted 1:1 by weight.
- Instant Yeast (IDY): The most concentrated form. It absorbs moisture rapidly and can be mixed directly into dry ingredients.
- Active Dry Yeast (ADY): Has a protective shell of dead yeast cells. It requires dissolving in warm liquid (blooming) before use and is slightly less concentrated than instant.
- Fresh Yeast (Cake Yeast): Has a very high moisture content (around 70%). It must be refrigerated and has a short shelf life, but provides excellent flavor.
Sourdough Starter Conversion Caveats
Converting a commercial yeast recipe to sourdough is complex. Sourdough relies on a symbiotic culture of wild yeast and lactic acid bacteria, which works much slower than commercial yeast.
Our tool uses a standard rule of thumb: ~14 grams of starter (100% hydration) for every 1 gram of instant yeast. However, you must also account for the flour and water present in the starter. For example, if the tool suggests 100g of starter, you should reduce your recipe's water by 50g and flour by 50g.
Note: Sourdough proofing times will still be significantly longer than commercial yeast, regardless of the amount used.
How Temperature Affects Yeast
Yeast activity is highly sensitive to temperature. The general rule in baking is that yeast activity doubles (or halves) for roughly every 10°C (18°F) change in dough temperature.
If your kitchen is significantly warmer than standard room temperature (20°C / 68°F), you can reduce the amount of yeast to maintain the original recipe's proofing timeline. Conversely, in a cold kitchen, increasing the yeast slightly can prevent excessively long rises.