The World of Yeast

I was reading the ingredients on the package of one of my favorite potato chips the other day and near the bottom of the list was “Torula Yeast”. As this is a very uncommon ingredient, I suspected many of you may have never heard of it. That spurred me to write this Cooking Tip about all kinds of yeast. It may be too hot right now to turn on the oven to yeasted items but it will not be too long before fall baking is something we all desire to do.

Before I explain the different types of yeast, let me mention the relationship between rising time (fermentation) and flavor. In our hurry-up world, we all seem to want results faster and faster. Even in the world of yeasts, manufacturers have developed products that lead to a faster rise. This may help you get that bread item on the table faster but it is often at the expense of a more complex flavor. Allowing your dough to slowly ferment, even overnight in the refrigerator, leads to more flavor. This may not be something we can or want to do all the time. Just realize that with convenience often comes decreased flavor.

Let’s start with the three major types of yeast followed by some newer creations. (One type that we will not be discussing as it is outside the scope of this Tip is a sourdough starter.) Today’s world of yeast is a bit confusing and I think, at times, the names are just a marketing ploy and do not necessarily translate to real differences between the types of yeast. That being said, let’s try to make some sense of this topic.

Fresh –this is also known as “cake” or “compressed” yeast. It is 70% water by weight and is composed of 100% living cells. It is soft and easy to crumble. To proof, allow it to soften in the water (95°-100°F) called for in your recipe along with a bit of sugar, which is food for the yeast. It should be foamy in about 10 minutes. Alternatively, you can add a teaspoon of sugar to the yeast and mix it together. If it doesn’t become looser, you can add just enough water to get it to loosen up. When it is bubbling, add it to your recipe.

It does produce the most carbon dioxide of any kind of yeast and yields a very distinctive flavor. However, it is not easy to find in most stores. It has a very short shelf life and so, you need to be aware of its expiration date. You can freeze this yeast but its activity may be lessened when you do you use it. You may need to use more or just accept a longer rising time. Before using the frozen yeast, allow it to come to room temperature before proofing it. Because this type of yeast is very moist, you may want to decrease the water in your recipe just a bit if the recipe was not written for fresh yeast.

Active Dry (ADY) – this yeast is 95% dry matter and is in the form of little granules made up of live yeast cells surrounded by dehydrated cells and a growth medium. This yeast requires proofing, which is rehydrating the granules in lukewarm water to activate them. This removes the dead cells that surround the live yeast. If the yeast is properly activated, it will foam after a few minutes in the water. If it doesn’t, don’t use it as your dough will not rise.

An interesting tidbit comes to us from King Arthur Flour. They say that the “classic ADY manufacturing process dried live yeast cells quickly, at a high temperature. The result? Only about 30% of the cells survived. Dead cells “cocooned” around the live ones, making it necessary to “proof” the yeast—dissolve it in warm water—before using. These days, ADY is manufactured using a much gentler process, resulting in many more live cells. Thus, it’s no longer necessary to dissolve ADY in warm water before using — feel free to mix it with the dry ingredients, just as you do instant yeast.” If this makes you nervous, go ahead and proof it first.

Instant – this is also in granular form, although smaller in size. It is about 95% dry matter. It undergoes a gentler drying process than active dry. This results in all the dried particles being alive. Its shelf life is at least 6 months in your panty and even longer when kept in the freezer. Instant yeast contains ascorbic acid, an ingredient not found in active dry yeast. It is a dough conditioner and is what makes the dough rise faster, improves the elasticity and increases the volume of the risen dough.

Its great advantage is that since the live yeast is not surrounded by dead cells, it does not require proofing in warm water. Just add it directly to the dough. It will activate quicker than other types as well as being a more consistent yeast. I know if you have been baking for a long time, it will be hard for you to skip this proofing step. I must admit that I see recipes that call for instant yeast and erroneously recommend proofing. It will not hurt anything to proof the yeast but it is an extra unneeded step.

RapidRise & Bread Machine yeasts are really just instant yeast. One of the manufacturers of these yeasts is Fleischmann’s (RapidRise is a name trademarked by them) and their website state that these yeasts are the same as each other and as instant yeast and can be used interchangeably. They explain these products in the following way – the yeast in these products is “grown with a higher level of nutrients and are dried to lower moisture content. The particle size of RapidRise and Bread Machine Yeast are finely granulated to allow complete hydration of the yeast cells during the mixing process … In addition, RapidRise and Bread Machine Yeast contain ascorbic acid resulting in increased loaf volumes.” This allows the baker to use the “rapid bake” cycle on bread machines. So, what is the difference between these two yeasts? Is there a difference, or as I mentioned, is it just marketing? To tell you the truth, I am not sure.

Because these yeasts are formulated to rise even faster than instant yeast, they are unsuitable for doughs that require a long rise, such as when you refrigerate the dough overnight. Neither are they good for doughs that undergo more than one rise. As I mentioned in the beginning, expect a blander and one-note flavor.

Pizza Yeast – this is a product made by Fleischmann’s. It is meant for people who want pizza dough in a big hurry and do not want to have to take the time to let the dough rise. It contains not only yeast but dough relaxers, which inhibit the formation of strong gluten strands. That allows the dough to be easily stretched and quickly rise in the oven.

The downside is flavor & texture. Cooks Illustrated found it to be “leathery, not crisp on the exterior and spongy and soft on the interior.” They also found the flavor to be very bland as one might expect with a dough that has very little fermentation time. A tester at tended to agree with this assessment.

Osmotolerant Yeast – this is a special strain of yeast that requires less water to function. Therefore, it is helpful in sweet doughs such as Challah. The sugar content of these doughs traps so much water that it interferes with activation of the yeast. If you make a lot of sweet doughs, you may want to consider trying this type of yeast as it will work faster than other types. The brand that is most available to home bakers is SAF in a gold package. Another brand is Instaferm.

Platinum yeast – this is a yeast marketed by Red Star. According to them, it is blended with “dough improvers” to make your dough more “forgiving”. Red Star’s regular instant yeast has the following ingredient list: “yeast, sorbitan monostearate, ascorbic acid”. Their platinum yeast contains “yeast, soy flour, ascorbic acid, sorbitan monostearate, wheat flour, enzymes”. So, as opposed to their regular yeast, it is not gluten free and also contains soy.

They also produce a Platinum Instant Sourdough yeast. Besides yeast, it contains sourdough culture. The ingredient list is “Cultured Rye Flour [rye flour, starter culture (Lactobacillus)], Yeast, Soy Flour, Ascorbic Acid, Sorbitan Monostearate, Wheat Flour, Enzymes”. It claims to give real sourdough flavor to your regular bread recipe. I have not tried it. If you have, let me know what you think.

Does the brand of yeast matter? Probably not as much as the type of yeast. Different manufacturers, though, might use different strains of yeast, which could mean different results. King Arthur Flour states that they do not like to use Fleischmann’s RapidRise. Even though the rising starts quicker than other brands, it also gives out sooner. They prefer SAF or Red Star because they like a longer rise, which leads to better flavor.

As with so many ingredients, I always recommend trying to stick with whatever is called for in the recipe. If you do need to substitute, here is a conversion chart.

Fresh yeastActive dry yeastInstant yeast
1 oz0.5 ozs0.4 ozs
—-1¼ teaspoon1 teaspoon

Cautions with yeast

  1. Don’t use hot water as it can kill the yeast. It should be lukewarm, 80-100°F.
  2. Try not to add salt before the first proofing as it also can kill yeast. If your recipe calls for adding things all at once, do not put the salt right on top of the yeast. I generally mix all the other ingredients first and then add the salt and mix again.
  3. Don’t use expired yeast.
  4. If you are substituting instant for active dry, you can add it directly to the dough but you should also add the water that your recipe would have called for in the proofing step.

All the types of yeast we have discussed so far are known as “Baker’s” yeast as we use them in baking. There is another type of yeast called “Nutritional” yeast. It has been heated to deactivate its leavening power. It is consumed by vegans and vegetarians as it is a source of Vitamin B-12. It also adds a savory flavor due to its high level of glutamic acid. Some use it as an alternative to salt, especially for sprinkling on popcorn.

Torula yeast – this yeast is also inactive as far as leavening ability but is very savory and somewhat smoky and adds a great umami punch to dishes. It has become a popular replacement for MSG (for a Tip on MSG, click here) in products that tout “natural” food products, such as my aforementioned potato chips.

Brewer’s yeast – this is what is used in brewing beer.

Whew, who knew there was so much to know about yeast? To tell you the truth, this Tip has probably just scratched the surface. I hope, though, it has given you the information you need to bake those great yeasted breads!