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Yeast 101

Active or instant? Slow rise or fast? Baker Peter Reinhart has the scoop on yeast.

by Peter Reinhart

fromFine Cooking
Issue 91

Yeast Tips

  • Instant yeast stays good, unopened, for at least a year.
  • When substituting instant yeast for fresh, use one-third the amount called for; that is, for every ounce of fresh yeast, use 1/3 ounce of instant.
  • To substitute instant yeast for active dry, use 25% less instant.

Differences in Yeast


I see so many different packets of dry yeast at the store. What’s the difference between active dry, instant, and quick-rise yeast? Are any as good as fresh yeast?

Tom Sevrin, Franklin, TN


Some bakers disagree about this, but nearly all breads and pastries will perform equally well with any of the available yeast products (fresh, active dry, quick rise, or instant). Active dry yeast, developed about 150 years ago, is sold in sealed, foil-lined packets. But in the packaging process, about 25% of the yeast cells die off, releasing a small amount of glutathione, which causes relaxation of gluten (this makes it a good yeast for pizza dough, but it’s not ideal for all dough products).

Instant yeast, also called quick rise or rapid rise, came along about 30 years ago and has become more popular as its availability has increased. Because none of the yeast cells die during packaging, it requires 25% less instant yeast than active dry yeast to leaven a loaf. The biggest advantage of instant yeast is that it dissolves directly in dough without having to be hydrated in warm water the way active dry yeast often does. (The mini baguette recipe uses active dry yeast without first hydrating it, but it works in this case because the dough is exceptionally wet.)

Fresh yeast, also called compressed or cake yeast, is sold refrigerated in foil-wrapped blocks and cubes. It’s a moist product and has a limited shelf life of about three weeks, even if refrigerated. It is also harder to find for home baking. Professional bakers have traditionally liked this type of yeast because it’s what they learned to bake with, but many of them are now switching to instant yeast because of its extended shelf life and ease of use.

Holding Bread Dough in the Refrigerator


Once bread dough rises, is there a way to hold the dough if you are unable to bake it right away?

Christine Barron, via email


Bread dough can be held in the refrigerator to slow down the rising, in a process called retarding. You can do this at various stages of the breadmaking process. The best time is after it’s had its first rise. Retarding actually improves the flavor of breads with low amounts of yeast and few or no enrichments (such as French bread), but with high-yeast and enriched doughs, the flavor will not be as good as if you baked it on the first day.

How to Avoid Overfermentation


Sometimes when I make bread (especially brioche) I notice a very strong, unpleasant alcohol taste in the finished loaf. What causes this and how can I avoid it?

Jennifer Davis, Lethbridge, Alberta, ca


What you are smelling is yeast fermentation—the conversion of sugars into alcohol and carbon dioxide. When dough overferments, it gives off a stale beer smell. Some of this alcohol will bake off, but some of it may remain in the finished bread. Dough made with a high percentage of yeast and sugar, such as brioche and other soft, rich bread products, are more vulnerable to overfermentation than crusty breads such as French or Italian bread, which use small percentages of yeast. If your bread is overfermenting it may be because the dough is too warm or, if kept overnight in the refrigerator, it did not cool down quickly enough to stop the fermentation. Try making the dough with colder water or reduce the yeast by about 10%. Brioche, especially, should be chilled immediately after mixing to control the fermentation.

Photo: Scott Phillips

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