Dry Yeast

Table of Contents

Introduction

Dry yeast for baking bread in ovens (at home) is normally dry baker’s yeast.

The use of fresh yeast (yeast cakes or compressed yeast) in home baking is rare – recipes or formulas that mention fresh yeast are decades old. Some commercial formulas and some reference materials refer to “fresh” yeast, compressed yeast cakes, the industrial product of cultivated yeast, processed and preserved in a wet medium, usually refrigerated.

In 1999, Beth Hensperger, in her Bread Bible said that the yeast on the market for the home baker included cakes of fresh yeast and dry yeasts:

  • active dry yeast. The inner yeast cells are active, unless the yeast has dried out and expired. It has to be “proofed” (activated) in warm water, and fed with sugar or starch;
  • instant – as of 1999, a new product from Europe. It does not have to be proofed in water – it is activated by contact with moisture in the dough; and
  • quick-rise and/or rapid-rise.

Beth Hensperger also mentioned, in her Bread Bible, bread machine yeast, manufactured by Fleishmann’s and Red Star. She said it was finely granulated and coated with ascorbic acid. If the manufacturers told her how bread machine yeast actually differed from instant and quick/rapid rise dry yeast, she did not say.

Most 20th century home baking books had been written with active dry yeast as the yeast to be used. It a dry powder. The particles are clumps of dormant living yeast organism, in shell of dead yeast cells. It needs to be exposed to water. The common practice, confusing called proofing, was to soak dry yeast in warm (not hot) water to break up the dead cell coating and revive the dormant living yeast

Instant yeasts, whether called instant, quick-rise, rapid-rise or bread machine yeast are dry yeasts make up of clumps of dormant cells, coated in chemicals. The clumps are smaller than clumps or grains of active dry yeast. It does not need to be proofed or activated. It become active on contact with water in a dough while the flour and water are mixed when the water dissolve the coating.

Recipes for home bakers generally use volume measurements.

Yeast: Science, Technical, historical

Yeast is a eukaryotic (single-celled) microorganisim. Yeasts are fungi. There are hundreds of species. The principal species used in processing carbohydrates in baking, brewing, and wine-making, and as a food product (nutritional yeast) is Saccharomyces cerevisiae (“S. cerevisiae”). Many varieties (“strains”) of S. cerevisiae are used in food processing, and are grown, processed, and marketed in different ways. Sources suggest that 1 gram of yeast contains about 20,000,000,000 (20 billion) individual yeast cells. This number will have been calculated from assessments of the number of cells in even smaller samples, which may have include some wet medium or dry coating.

Brewers differentiate: yeasts that form a film on top of a wort like S. cerevisiae are ale yeasts. Yeasts that accumulate and ferment on the bottom of a wort are yeasts for lagers.

The beginning of brewing and baking were historically related. However, the history of food was largely not recorded. Yeast infested grain mashes. Yeast consumed starch (fermentation) producing carbon dioxide and alcohols. Carbon dioxide trapped in webs of gluten, makes bread rise. Alcohols flavour bread, and have other purposes. These accidents started cycles of experimentation, learning and imitation.

At some points, bakers obtained yeast by buying by-products of brewing. Industrial yeast production in the 18th and 19th century produced compressed or “caked” fresh yeast in blocks or “cakes” to industrial bakers.

By 1999, yeast manufacturers were introducing new dry yeast products to the market. Mergers and acquisitions realigned brands. The American brand Red Star was sold to the European manufacturer LeSaffree. The proliferation of types and names arose because manufacturers used different techniques and marketing terms. The manufacturers do not explain (to retail consumers and home bakers) how rapid/quick-rise, instant yeast and bread machine yeast products are made, or how they differed. Bakipan, another American brand acquired by Lesaffre, for instance, says that its “Fast Rising Instant Yeast [is] … cake yeast in a semi-dormant state. The drying process in its manufacture reduces moisture content, giving it a longer shelf life than cake yeast while retaining optimum activity. … Bakipan® Fast Rising Instant Yeast is a fast-acting yeast that can shorten the rise times for traditional baking …” Specifications and methods are not noted on the packaging or published widely – perhaps only for some customers.  The manufacturers don’t, according to what home bakers say on the Web, respond to inquiries from home bakers.

Dry Yeasts

Measurement

For cooking and baking measurement of active dry yeast, likeother ingredients for home cooking, was and is usually by volume. The teaspoon is the normal unit of measurement. A teaspoon is exactly 1/3 of a Tablespoon. The exact metric conversion, to the nearest .1 millilitre is 4.9 ml. It is common for spoons to be marked indicating that 1 teaspoon is 5 ml., 1 Tablespoon is 15 ml., ½ tsp. is 2.5 ml., etc.

Some reference materials provide general comparison of the weights of fresh yeast and the varieties of dry yeast.

Peter Reinhart, the author of popular books on artisinal technique for home baking, suggested at p. 15, in Crust and Crumb (1996), that active dry yeast and instant yeast weighed about 40% and 33%, respectively, of the equivalent amount of fresh yeast. At p. 28 in The Bread Baker’s Apprentice (2001), Peter Reinhart the values differently. The values:

ProductWeight (C&C)Weight (BBA)Volume (C&C)Volume (BBA)
Fresh1 oz.1 Tbsp.
Active dry.4 oz.1.25 tsp
Active dry.1 oz.1 tsp.
Instant.33 oz..11 oz.1 tsp.1 tsp.

Daniel Di Muzio, in Bread Baking, An Artisan’s Perspective (2010), said:

You need only about half the weight of [active dry] yeast called for in formulas that specify fresh yeast. …. The conversion factor [for instant yeast] versus fresh yeast is even lower. You only need 33-40 % as much instant yeast as fresh yeast …

Active Dry

Active dry yeast was developed in the 1940s. Active dry yeast was durable for months or years without refrigeration, unlike the compressed fresh yeast used by industrial bakers. Active dry yeast was and is manufactured by drying a yeast culture. The dried yeast was made up of “grains” resembling fine sand, which are actually clusters of thousands of yeast cells. The exterior of the grains was/is made of dead cells. The live dormant interior cells can be activated by putting the dry yeast in warm (not hot) water. This product had and has a serious expiry date. Active dry yeast was and is sold in 1/4 oz. (U.S.) packets. In the US a 1/4 oz.packet was 1 Tbsp. For some years one packet 2.5 tsp. As of about 2001 it was 2.25 tsp. Old packets of old style active dry yeast have not been manufactured or sold for decades.

Active Dry

Active dry yeast was developed in the 1940s. Active dry yeast was durable for months or years without refrigeration, unlike the compressed fresh yeast used by industrial bakers. Active dry yeast was and is manufactured by drying a yeast culture. The dried yeast was made up of “grains” resembling fine sand, which are actually clusters of thousands of yeast cells. The exterior of the grains was/is made of dead cells. The live dormant interior cells can be activated by putting the dry yeast in warm (not hot) water. This product had and has a serious expiry date. Active dry yeast was and is sold in 1/4 oz. (U.S.) packets. In the US, a 1/4 oz.

packet was 1 Tbsp. For some years one packet 2.5 tsp. As of about 2001 it was 2.25 tsp. Old packets of old style active dry yeast have not been manufactured or sold for decades. Bread recipes from the 1940’s until the introduction of the other dry yeast varieties refer to active dry yeast. Many specify with amounts of active dry yeast in packets or by measuring spoons, by volume. Active dry yeast is measured to the nearest quarter teaspoon in many home baking recipes and bread machine recipes.

Instant Yeast (and variants)

Instant yeast “grains”mail are smaller than grains of active dry, and chemically coated in ascorbic acid (Vitamin C) and sugar. Instant yeast activates on contact with the water when the dry ingredients are mixed with the wet ingredients, and almost never needs to be activated or prehydrated to propogate. See All About Dried Yeast, What is Bread Machine Yeast, the King Arthur flour Ingredient Guide, the King Arthur web article All About Yeast, and the King Arthur blog post “Which Yeast to Use”. See also Commercial Yeast in Fresh Loaf Baker’s Handbook, and What’s the Difference between Active Dry Yeast and Instant Yeast. For the history of baking yeast, and the ways it has been presented, Lesaffre’s Explore Yeast pages are informative.  A leading baking industry paper on instant yeast: Lallemande’s Update, Volume 2 # 9.

Beth Hensperger mentioned instant yeasts sold as Regular Instant and Special Instant in her 1999 Bread Bible. Looking back, it is not possible to identify the manufacturer. Lesaffre brought instant yeast to the market in the U.S. under its own SAF brand. It manufactures and promotes SAF Instant Red and SAF Instant Gold. The Gold product is osmo-tolerant, and said to be “designed especially for doughs high in sugar (sweet breads)”. Lesaffre distributes SAF brand yeast to home bakers in the US through quasi-wholesale mail-order and online vendors like King Arthur Flour as a specialty baking product. Generic and store-branded instant yeasts are available.

Increasingly, general bread recipe books are written for instant yeast, also by volume. Books on artisinal bread baking do not distinguish quick-rise/rapid-rise yeast from instant yeast. Peter Reinhart said that instant yeast can be substituted for compressed fresh and active dry yeast for home bread baking, and for artisanal recipe uses. He came to accept that instant yeast should be rehydrated for artisanal breads in Artisan Bread Every Day (2009) at p. 13 (although fermentation should be slowed down with refrigeration to develop flavor and other features of artisinally baked bread). Other writers agree. See:

  • Peter Reinhart, Crust and Crumb (Ten Speed Press, 1998);
  • Peter Reinhart, The Bread Baker’s Apprentice (Ten Speed Press, 2001);
  • Peter Reinhart, Artisan Bread Every Day (Ten Speed Press, 2009);
  • Robert DiMuzio, Bread Baking; An Artisan’s Perspective (Wiley, 2010).

Some recipe and baking books suggest letting the yeast and ingredients warm to room temperature. Refrigeration preserves the product. Some  sources suggest that keeping yeast cold, including dried yeast, slows it down. Reinhart noted that instant yeast is potent but slow to awake in The Bread Baker’s Apprentice at p. 32, and in later books began to suggest putting instant yeast in warm (not hot) water was useful.

Quick-rise/rapid-rise yeasts are dried and coated differently than “instant” yeast, depending on the manufacturer or processor. Some have the words “Instant Yeast” on the label. See: Yeast: Dry vs. Rapid-Rise and the thread “Fast Active Fleishmann’s vs. SAF Instant” (about pizza dough). The equivalences were debated in forums like Instant Yeast vs. Fleishmann’s Rapid-Rise.

Peaks

Yeasts, once they activate, ferment and propogate, pick up speed and hit a peak. Some compressed and active dry yeasts have a second peak – home wine makers and home beer makers encounter this with their yeasts which have a vigorous first fermentation and a secondary fermentation. Bakers may time their bulk fermentation and final proof to take advantage of each. I found a graph on SAF instant yeast gas production (with the Cyrillic text and the red line for SAF in the post by Mariana January 2, 2018 in the forum Difference in Yeast Brands). I have not found comparison graphs for other instant yeasts.

Converting Active Dry to Instant

In 1999, Beth Hensperger, writing in her Bread Bible said that a quarter ounce (US Units) “packet” of active dry yeast was a Tablespoon. Modern active dry yeast grains are finer, and the product is more dense. Modern active dry yeast is still sold in quarter ounce packets. For a few years, a quarter ounce converted to 2.5 tsp. (.83 Tbsp). More recently, leading brands Fleishmann’s, Red Star (Lesaffre), SAF (Lesaffre) state that their quarter ounce packet of active dry yeast contains 2.25 tsp.

The amount of current active dry yeast to substitute for a packet of active dry in a recipe can be determined easily:

  • A quarter ounce packet is still a quarter ounce packet;
  • A home baker with a jar of modern active dry yeast can scoop 2.25 tsp. of modern active dry to substitute for a “packet” of active dry in an old recipe.

Converting a specific amount by volume – e.g. 2 tsp. – of active dry yeast in an old recipe to modern active dry yeast, or to instant yeast will involve parsing the recipe to determine what an author meant, and a little math.

Differences between active dry and Instant yeast:

  1. Instant yeast has smaller particles; it is denser. 1 tsp. of instant is heavier than 1 tsp. of active dry. Online sources say that 1 tsp. of instant is 3.1, 3.12 or 3.15 g,;
  2. Instant yeast has less coating and has more active yeast cells. It starts fermenting faster and is more “potent”;
  3. Instant yeast is harder to weigh. 1There is a problem filling a true teaspoon – or even verifying that a teaspoon measures exactly 4.9 ml. Many manufacturers make a teaspoon that measures 5 ml. It is necessary to weigh repeatedly with a verified teaspoon and average the readings. There may be variation depending on how the yeast has been processed and handled, and temperature. I measured SAF Instant Red, and thought 1 tsp. was 2.8 g. I tried again SAF Instant Red again and got weights from 2.95 to 3.32 g. for 1 tsp. It may be ≧3.3 g. for other brands. I use the standard 3.12 g. as 1 tsp.
Product (1 tsp.)Weight, U.S. oz.Weight, (metric) grams
Active dry0.12.83
Instant0.113.12
Online sources say that 1 tsp. of instant is 3.1, 3.12 or 3.15 g.

Substituting dense, more potent instant yeast for active dry means less volume and a decrease in weight. The bakers’ rules of thumb at the end of the 20th century for converting instant and (modern) active dry yeast by volume were:

  • 5 parts active dry = 4 parts instant. 1.25 tsp. active dry = 1 tsp. of instant, per Peter Reinhart; and
  • 4 parts active dry 3 parts instant. 4 tsp. active dry = 3 tsp. of instant.

The 5 parts to 4 ratio suggests that the amount of instant yeast to substitute for active dry yeast is 4/5 (80%) of the active dry yeast. The ratio may be 6/7 (86%). Either ratio is close enough to be useful, if a home user mixing enough ingedients for one or two loaves can be precise whether measuring by volume or by weight.

Conversion of active dry yeast in a recipe by weight is simple, if a baker is sure that a recipe refers to active dry yeast that was as effective as modern active dry yeast, which weighs 2.83 grams per teaspoon, has a scale that is precise enough and knows the right conversion factors. 1 tsp. of active dry yeast might be converted 2.1 grams of instant yeast. 80 or 85% of 2.83 g. would be 2.3 g. or 2.4 g.

Any given online converter may not use accurate information about the products, or make rounding errors. [Update -the Omni calculator, as of late 2022, is fast and close enough to be useful with the amounts used to mix dough for 1 or 2 large or medium loaves.]

More conversions, not entirely consistent. These cannot be easily measured with measuring spoons or weighed without a very precise scale:

Active dry
tsp.
Active dry
US oz.
Active dry
grams
Instant
grams
Instant
US oz.
Instant
tsp.
7.02.252.25
2.57.06.71.242.15
2.25
1 packet
after 2005
.256.46.2.222
5.51.75
2.25.664.2.18
1.754.93.65
1.54.253.13
3.12.111
1.25.1253.52.6
1.12.832.1.86
1.6.06.5
.752.11.4
.5.051.41.3.43
.8.03.25
.25.025.7.5

Bread Machine

Instant yeasts, rapid/quick-rise yeasts, and bread machine yeasts vary in some ways, but are equivalent for bread machines. Beth Hensperger suggested using bread machine yeast in bread machine recipes in the Robotic Kneads chapter of her Bread Bible. In The Bread Lover’s Bread Machine Cookbook, Bread Hensperger suggested that SAF brand instant yeast was a more efficient yeast for bread machine baking, providing different amounts of yeast for instant yeast and bread machine yeast for individual recipes. This advice was not helpful.

I use instant yeast in my bread machine (and for all bread baking).

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