Active dry yeast (ADY)

About

Active dry yeast is the older granular form — larger particles than instant, with a protective layer of dead cells that must be hydrated in warm water (100–110 °F) for 5 minutes before mixing. It's interchangeable with instant dry, but you need about 25% more by weight, and you have to hold back a portion of your recipe water for the proof. Most modern brands have improved enough that the proofing step is functionally cosmetic, but if your packet is older, the proof confirms the yeast is still alive (foamy, smells beery).

History

Active dry was developed during World War II by Fleischmann's for the U.S. military — bakeries needed a shelf-stable yeast for forward operations. Instant dry, refined in the 1970s in France, eventually displaced it for most commercial baking.

Substitutes

• Instant dry yeast (IDY) — use 0.8×; skip the proof step