From the production of bread to the brewing of beer, yeast fermentation plays a critical role. Known scientifically as saccharomyces cervisiae, yeast is a single-cell microorganism that converts sugar to carbon dioxide and alcohol. The fermentation process causes bread to rise.
Yeast is commonly available in three forms -- active dry, instant dry and fresh. Active dry yeast is granules that went through a harsh drying process; in every 1 lb. of the yeast, 1/4 of the cells are dead. Instant dry yeast also is in granule form but went through a much gentler drying process, killing fewer yeast cells. Fresh yeast is in compressed blocks that contain about 70 percent moisture.
As a result of yeast forms' differences, recognizing a yeast type and making accurate conversion measurements is important.
Things You'll Need
- Scale that measures grams
Converting Fresh Yeast to Active Dry Yeast
Weigh the required amount of fresh yeast. Calculating the amount in grams rather than ounces is helpful for a more accurate measurement.
Multiply the weight of the fresh yeast by 0.4. This result is the scaled amount of active dry yeast required. If the yeast manufacturer provides a different scaling factor, then it is better to use its ratio for conversion.
Dissolve the active dry yeast in four times its weight in water before use. The water temperature should be between 105 to 115 F.
Converting Fresh Yeast to Instant Dry Yeast
Weigh the required amount of fresh yeast using a grams scale
Multiply the weight of the fresh yeast by 0.33. The result is the amount of instant dry yeast required. Instant dry yeast can be incorporated directly into dough without being dissolved first.
Multiply the weight of the fresh yeast by 0.77. The result is the amount of water that should be added to the final product to make up the moisture difference between the fresh yeast and instant dry yeast.
Tips & Warnings
- To reverse the calculations from instant dry yeast or active dry yeast to fresh yeast, simply divide, rather than multiply, the weights by the appropriate scaling factors.
- This equation can be helpful: 3 tbsp. dry yeast = 28.34g.
- Do not put yeast in direct contact with salt. It inhibits fermentation. Typical yeast dough contains 1.8 to 2.5 percent salt.
- "How Baking Works: Exploring the Fundamentals of Baking Science"; Paula Figoni; 2008
- "Bread: A Baker's Book of Techniques and Recipes"; Jeffrey Hamelman; 2004
- "Professional Baking"; Wayne Gisslen; 2009
- Photo Credit Jupiterimages/Comstock/Getty Images