All the Different Kinds of Yeast, and What You Really Want for Baking Bread

Thanks to COVID, people all over the country discovered the joys of baking bread, as well as the sorrows of futile attempts at procuring yeast, followed by even greater sorrows with failed loaves of bread due to using the wrong kind of yeast.  One might even guess that given the ongoing food shortages in the US and the potential for even greater scarcity in the coming months, yeast may be hard to locate at times.  But if you know how each type works, no one will detect any differences in your final products.

There are a lot of different kinds of yeast.  Most serve different purposes.  Some can be used interchangeably with little difficulty, while others cannot.  Here's what you need to know, at least as far as bread baking is concerned.

The different types of yeast 

• Brewer's yeast is a byproduct of the brewing industry.  After being used for making beer, it becomes incorporated into animal feed, food flavoring, or nutritional yeast.  It is a dry, inactive yeast without any leavening ability.  It is high in many B vitamins and is sold as a nutritional supplement.[1]
• Distiller's or wine yeast is for making alcohol, not bread.  It is bred for producing alcohol, not carbon dioxide, the gas that causes bread to rise and makes it light and fluffy.  It has some leavening ability, not much, so it takes much longer for bread to rise.
• Nutritional yeast has no leavening ability.  Some manufacturers sell it strictly for its vitamin and protein content in both powder and pill forms.  Others market it for use in food as a flavoring to substitute for chicken broth.[2] 
• Bread yeast is what we want for bread, and that's what the remainder of the article will focus on.

The different types of bread yeast
Now there are the numerous types of bread yeast to consider and the pros and cons of each so that you can make the best decisions for your family food storage program.

• Natural yeast is also known as wild yeast.  Unlike all the other forms of yeast, you cannot see natural yeast with the naked eye.  We only know it's there when then flour and water start to bubble.  The most well-known of the natural yeasts is sourdough.  It is what everyone used until the 1900s when scientists first isolated yeast and could then produce commercial yeast.  Keep in mind that bread from a sourdough yeast starter doesn't have to be sour--it all depends on how you work with it.  That's a topic for another post.  One cup of sourdough starter is the equivalent of 1 package of dry yeast (2 1/4 teaspoons).  Keep in mind that the quantities of flour and water in the recipe will have to be reduced.
• Fresh yeast is soft and moist and must be refrigerated, so it's not a good choice for food storage purposes.  It goes bad much more quickly than the other types and must be proofed (that's French for dissolved in water) before mixing with the other ingredients.  Fresh yeast will produce the most carbon dioxide and is more reliable and potent.[3]  If using a recipe that calls for dry yeast, you need double the amount of fresh yeast to substitute.  
• Dry yeast comes in several forms.  All of these forms should be stored in airtight containers in the refrigerator or freezer to extend shelf life. Proofing yeast is always a good idea. It's important to make sure that the yeast cells are still active and effective--that they will metabolize the sugar and produce carbon dioxide to raise the bread.
• Active dry yeast comes in little pellets about the size of poppy seeds.  Active dry yeasts are exposed to high heat that actually kills off the outer cells.  This yeast must be proofed in very warm water, about 105 degrees, to dissolve or slough off the outer layer of cells and reach and activate the yeast cells in the center.[4]  If this yeast is not proofed, it may not dissolve in the bread, your bread won't rise as well, and someone may bite into an undissolved pellet.  Not good.  Not tasty.  The process of proofing will also show that the yeast is still active.  This yeast is the one most commonly used commercially and works well in most recipes.[5]  
• Instant yeast is subjected to the same kind of drying process as active dry yeast, but at lower temperatures so that nothing is killed.  It doesn't need the sloughing off period of the active dry yeast and is ready to begin work right away.  While it doesn't need to be proofed, it's still a good idea to proof it and make sure the yeast is still good before adding in other ingredients.  This yeast isn't as sensitive to the water temperature, and bread will rise fairly quickly.  According to official sources, instant yeast will store for up to a year at room temperature.  (I've stored it for years in the freezer.)  Instant yeast also has additives, up to 7%, to enhance the dough.  SAF Instant Premium Yeast adds vitamin C to extend the shelf life.  Active dry yeast has a different flavor due to the dead cells (and opinions vary as to whether this is good or bad).  This difference in flavor isn't noticed in breads made with sugar, milk, and butter.[6] 
• Rapid rise yeast (also known as quick rise, bread machine, easy bake) is definitely faster, easier, and more convenient to use.  It's readily available at grocery stores.  Most describe it as a fine powder in appearance, and because it is a powder it doesn't need to be proofed before adding the other ingredients.[7]  This dissolves the fastest, so bread rises faster and is ready to bake sooner.  It's usually what is used in automatic bread machines.  Note that the speed of the rise may affect the taste of the bread.

All forms of dry yeast may be used interchangeably in recipes.  Some professionals say they can be substituted measure for measure.  Others recommend a bit of adjustment for best results:

• To substitute active dry yeast for instant, use 25% more, i.e., if the recipe calls for 1 teaspoon instant yeast, use 1 1/4 teaspoons active dry yeast.  
• To substitute instant yeast for active dry yeast, use 25% less, i.e., if the recipe calls for one package (2 1/4 teaspoons), use 1 3/4 teaspoons of instant yeast.  There is no need to proof it--just add it in with the other ingredients.[8]

Proof yeast in the following manner:  Dissolve the total amount of yeast the recipe calls for in a portion of the warm water (body temperature is great, or perhaps a tiny bit warmer) that will be used in the recipe.  Add a teaspoon of sugar to feed it.  Let set for 10-15 minutes.  The mixture should bubble nicely, indicating the yeast is still alive and effective.  If it does not, the yeast is no longer good and should be discarded.

Notes.  If making a sweet dough like cinnamon buns or brioche, increase the amount of instant yeast by about 30%.[9]  North American and Scandinavian recipes generally call for more yeast than average.  This makes breads rise faster and they may taste yeasty.  However, bread that rises slower is easier to digest. 


References: 
[1]https://redstaryeast.com/science-yeast/types-of-yeast/brewers-yeast/
[2]https://redstaryeast.com/science-yeast/types-of-yeast/nutritional-yeast/
[3] https://www.cooksillustrated.com/how_tos/6620-yeast-types
[4] https://www.epicurious.com/expert-advice/swap-different-types-of-yeast-article
[5] Ibid. 
[6] https://www.cooksillustrated.com/how_tos/6620-yeast-types
[7] https://www.epicurious.com/expert-advice/swap-different-types-of-yeast-article
[8] https://www.cooksillustrated.com/how_tos/6620-yeast-types
[9] https://www.tasteofhome.com/article/all-about-yeast/

 9.18.20