a brief history of yeast, part two

February 18, 2018

FINALLY- I am finishing this post on yeast. And I've decided not to write a two part post again unless I write both parts at the same time. Someone hold me to this, please.

That being said, I'm just going to dive right in where I left off in part one.

As you near the end of the commercial yeast process, you have a form of yeast called cream yeast which is ready to be further processed to become one of three final forms: fresh yeast, active dry yeast, or instant yeast. Let's go over these three forms of yeast.

Fresh yeast or cake yeast is the least processed of the three. It has a high moisture content and expires within about eight weeks of processing. It must be refrigerated at all times. As the least processed form of the three, it is also has the most leavening power. I've honestly never used fresh yeast (or even seen it at a standard grocery store) so I'm not going to spend any more time talking about it. Moving on!
a block of compressed fresh yeast- so different looking from its more processed counterparts! image credit: by hellahulla (own work) via wikimedia commons
Both active dry and instant yeast require one last step of drying. Active dry yeast, along with some of the leftover nutrient debris, is dried at a high heat. During this drying process, the debris forms a protective covering around the clumps of yeast. Because it is dried, active dry yeast has a lower moisture content than fresh yeast, making it shelf stable. However, the protective covering of debris puts the yeast in a semi-dormant state, which is the reason that you have to activate it by soaking it in warm water. Soaking or proofing active dry yeast wakes it up by dissolving the debris covering (see next paragraph for a more thorough explanation). Active dry yeast is dried at such a high heat that many of the yeast cells are killed in the process. Approximately 25% of yeast cells in a canister of active dry are already dead when you buy it (and this doesn't include the debris that is surrounding the yeast cells- so most of your 'yeast' in a canister of active dry is not yeast at all!).

To use active dry yeast, you must first dissolve it in warm water (about 110 degrees F) for several minutes. During this time, the mixture should bloom, or begin to foam and grow in volume. This signifies that the yeast is still alive and will have the power to make your bread rise. If nothing happens during this time, the yeast is not good and should be tossed out (otherwise you will be super bummed at the end of your baking experience). Most recipes that call for active dry will include this step in the recipe directions. However, if it is not included or you are subbing in active dry in a recipe that calls for instant yeast, make sure you measure out how much water you use to dissolve the yeast and subtract that from the total liquid called for, or it will throw off the recipe's proportions.

Finally, we get to instant yeast, my go-to yeast! About 30 years about active dry yeast was invented, French yeast manufacturer Lesaffre developed instant yeast, which launched in 1973 under the name SAF-instant, which is still available to this day. Instant yeast is dried in a very similar manner to active dry yeast, but at a lower heat, so the drying is gentler, and all of the dried yeast will be alive/active when it comes to you. It is not surrounded by debris like active dry yeast. Instant yeast is the variety of yeast that goes by many names and is often called fast rising yeast, rapid rise yeast, or bread yeast. There are several prevalent misconceptions about instant yeast, which I would like to discuss. 
remember this photo from yeast, part one? this is my go-to yeast. also showcasing my messy fridge in the background!
Myth #1: Instant yeast and active dry yeast can be substituted at a 1:1 ration

This seems super logical, right? I just told you that both forms of yeast are made in the exactly same way- the only difference being the temperature at which they are dried. It is actually because of this difference in processing that you need less instant yeast than active dry. Instant yeast is more concentrated. It contains about 25 percent more living yeast cells per spoonful than active dry yeast. In my opinion, you're getting more bang for your buck when you buy instant yeast because of this.

Interestingly, if you google "substitute active dry yeast for instant" many of the website that come up will tell you that you can substitute at a 1:1 ratio, even some websites that I normally trust and often use as a resource. They claim that the active dry yeast will just be a little slower in getting the dough to rise. I guess that's technically true- you can substitute at a 1:1 ratio without epically disastrous results. But should you? Now that's an entirely different question. And the answer is: no. You should not. Luckily, it's pretty easy to figure out how much of whatever you're subbing to use- use 25 percent less yeast when subbing instant for active dry. 

So, if your recipe call for 1 tablespoon of active dry yeast, you would only use 2 1/4 teaspoons of instant yeast. Alternatively, if you are going the other way, you would want to increase the yeast by 25 percent. If a recipe called for 1 tablespoon of instant yeast, you would want to use 3 3/4 teaspoons of active dry yeast.

As you can see from the numbers above, if you're making a recipe that calls for a small amount of yeast, the substitution ratio doesn't make a huge difference. However, if you're making a recipe with a large amount of yeast- for example if you were doubling a bread recipe that originally called for 1 envelope, or 2 1/4 teaspoons, of instant yeast and you subbed in active dry, you would need to add over a teaspoon- so yeah, the substitution ratio is kind of important!

Myth #2: Instant yeast provides a 50% faster rise time

As I mentioned above, many sources claim that you can sub active dry and instant for each other in a 1:1 ratio and the only difference is that the active dry rise will be a little bit slower. Let's dissect what this statement truly means for your baked goods.

We've already discussed how instant yeast is subjected to a gentler drying process, and therefore all yeast cells are still active, as opposed to active dry, which will only have about 75% active cells. So that right there is your answer- if your recipe calls for 1 teaspoon of active dry yeast, and you substitute 1 teaspoon of instant yeast, it's like adding 1 1/4 teaspoon of active dry. That's why it's faster- you are literally increasing the proportion of yeast in the recipe. Of course it will work faster! In theory, that's great- who doesn't love a good shortcut? But this is not a good shortcut. Depending on what kind of bread you are making, the length of the rise is crucial to your finished product. 
hotdog buns. these are an enriched dough, getting their flavor from the eggs and milk. 
Why a slow rise is important and necessary

If you're making an enriched dough (if there are additives such as eggs, butter, milk, etc), your rising time isn't as crucial to the flavor of the bread. This is because much of the flavor will come from the additives. It's still necessary to include any rises called for in the recipe as they are structurally important for your dough. That said, you can feel free to slightly speed up the rise by putting your dough in a warmer spot in your kitchen or maaaaybe increasing the amount yeast by a teensy bit (honestly, I still wouldn't recommend this). If you are trying to speed up the rising time, you should use the growth of the dough as an indicator for when it is ready to be shaped- usually you want it to double in size. 

However, if you are making a lean dough (no enrichments such as butter/milk/eggs are included), the long rise time is crucial to the flavor of the finished product. This is because all of the flavor in the bread is being developed during the rising time. The longer the rise, the more complex flavor you will have.

Rising time is also known as proofing or bulk fermentation. Technically speaking, in the bread world 'bulk fermentation' refers to the initial rise of the dough and 'proofing' refers to the second and final rise when the dough has been shaped. That said, most people who are not professional bakers use all three terms interchangeably, myself included. However, knowing the name of the first rise - fermentation - does give us a very good clue about why this step is the flavor-maker. By definition, fermentation is the production of alcohol. During the bulk fermentation period, the yeast is consuming sugars in the dough and expelling carbon dioxide and alcohol. The carbon dioxide provides structure to the dough as the bubbles of CO2 expelled are trapped in the matrix of gluten. The alcohol provides the flavor. Fermentation is an anaerobic reaction, so the yeast only begins to expel alcohol after its oxygen supply has been depleted. If you cut your rising time short, your dough will have structure from the CO2 but will not have much flavor because there wasn't time for the yeast to produce much alcohol.

Conversely, letting dough rise for too long causes it to be overproofed. This means the dough becomes over-aerated and the CO2 bubbles that we normally love and praise for providing structure to our bread actually overpower the gluten structure. Overproofed dough will be totally lacking in oven-spring and will probably have a disappointing uniform crumb. 

I didn't explain the dangers of under/overproofing dough just now with the goal of scaring you away from ever making a loaf of bread again. Actually, quite the opposite. I want you to feel extremely confident that if you follow the recipe and stick to the recommended proportions, you will come away with an amazing, flavorful, well-proofed loaf of bread. If you're looking for an different outcome than what your recipe is offering, find recipes that include steps to achieve your desired results (fast rise/slow rise/more flavor/etc) rather than tinkering with a recipe. Altering the formula of a bread recipe can be pretty dangerous if you don't understand exactly why you're changing what you're changing. There are some recipes I'll change slightly, but in general I still don't feel knowledgable enough about this stuff to mess with a recipe too much. 

Finally...

Remember to always store your yeast in the fridge or freezer once it has been opened. This is necessary because as soon as a container of yeast has been opened, it will slowly begin to absorb moisture from the air (remember- it's grown and packaged under extremely strict and hygienic conditions). This will cause it to become activated. If you try to use it in dough after this has happened, it will have lost all of its potency and won't give a good rise to your bread. Personally, I love buying the one pound red and blue SAF bags of Lesaffre yeast (pictured below). They are very cost effective and will last forever (literally years, depending on how often you use yeast) in the freezer.
SAF-instant, my favorite brand of yeast, next to King Arthur AP flour, my favorite brand of flour!
I'll finish this long-overdue post with two very different but very good bread recipes. The first, Oatmeal Bread, is an enriched dough. It takes its flavor from the eggs and butter and therefore the rising time is important in terms of structure, not flavor. The second is a very well known no-knead dough from Jim Lahey. In fact, this recipe is credited with starting the no-knead revolution. I chose it because A) it's delicious, and B) it's historically important, and C) it's an excellent example of a loooong rising time leading to an amazing flavor. You do have to plan ahead on this one, but it also happens to be very hands-off. To achieve the best results, you should bake it in a dutch oven. A baking stone will suffice if a dutch oven is not available. Click here to go to the recipe post!

Note: Since I tend to write such long posts, I've decided to start including the accompanying recipes in separate posts. The goal is to make it easier to get straight to the recipe if you've already read the above information and just want to get straight to baking!

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