Originally, this was supposed to be a quick two or three paragraph post. In fact, the first sentence I just deleted said something like "This post will not be very long, but it is still an important topic!"

Well.

Some have called me loquacious. It could be somewhat true. I've always found it difficult to write a short letter or email. It seems that wordiness is in my nature. Another problem is that every time I decide to post on a topic, I become determined to learn as much about it as I can. In fact, I created a flow chart to illustrate how off topic I can sometimes get when working on a new post (spoiler alert: it ends with creating a flow chart... ). As my interest in learning about yeast grew while working on this, I eventually realized I was covering a little too much information for one post, so I decided to break it into two. This first post will cover a bit of history as well as a brief explanation of the commercial production of yeast. The question that we are ultimately working towards answering is: why on earth are there so many different kinds of yeast out there?


You may have noticed that there are several different names on the yeast found in that tiny corner of a shelf allocated to yeast at the grocery store. Instant yeast, active dry yeast, RapidRise, Quick-Rise, and bread machine yeast are just a few of the names you might see. Fresh yeast is another type of yeast you may see in a cookbook or online, but you likely won't find it on that little shelf since it must be refrigerated.

My theory is that yeast companies purposely try to come up with as many names as possible for the same product (yeast) in order to convince consumers that they need to keep about six different kinds of yeast on hand at any given time. ("Oh no! I want to make bread in my bread maker but I'm all out of bread machine yeast - must run out to the store and buy some immediately!") It's definitely a conspiracy, and don't even get me started on all of the conspiracies out there (Just kidding) (Maybe).

alllllll the different kinds of yeast at kroger (and a lil bit of corn starch)

Let's back up. Yeast. What is it, anyways? Yeast is a eukaryotic microorganism that originated about a gazillion years ago (literally hundreds of millions of years ago). There are around 1,500 different species of yeast out there, but the one that I love most is Saccharomyces cerevisiae, commonly known as brewer's or baker's yeast. S. cerevisiae has quite a few different applications (protein supplement, immune enhancer, some studies even show it to be a successful component of preventive medicine). In fact, it is so freakin' important that it was actually the first eukaryotic organism to have its entire genome sequenced. In case you were wondering (as I was), the sequencing was completed in 1996 by The International Collaboration for the Yeast Genome Sequencing. All these impressive facts about S. cerevisiae aside, I am focusing here on its awesome ability as a fermenter.

Cells of yeast are very, very, very small. They are so small, in fact, that it's almost impossible to describe how small they are. Here's my analogy for it: if you replaced every single person on the surface of the earth with a cell of yeast, you could fit the entire world's population in a one cup measure. Umm.... whoa. Honestly, you could probably even throw in all of the aliens living on Mars along with them and still have room to spare.

teensy tiny cells of yeast. image credit: bob blaylock via wikimedia commons

Baker's yeast's main purpose is as a catalyst. It facilitates the fermentation process, which is crucial in bread making. When it is added to a dough and activated, the yeast will begin to feed on the sugars in the dough. As it does this, it expels carbon dioxide. Since the CO2 really has nowhere to go as it is trapped in a matrix of starches, it simply expands right where it is, making thousands of CO2 bubbles, causing the dough to expand and lighten (aka letting the dough rise). During the baking process, the starches gelatinize and set and the yeast dies, leaving behind a web of empty bubbles.

Now that I've given you a very brief description of yeast's importance and how it works, let's get back to the question at hand - why are there so many different kinds of yeast out there? Honestly, there is really only one type of yeast you should ever want or need, and that's instant yeast. If you've been spending your days toiling away dropping bits of active dry yeast in tepid water and then waiting to make sure it blooms, this little nugget of information is going to blow your mind. Let me explain the difference between active dry and instant yeast.

active dry yeast vs instant yeast (vs pizza crust yeast?)

Active dry yeast is probably what your grandma uses to make bread- many people are more familiar with this type of yeast and thus feel more comfortable using it. To use active dry yeast, the first step you must always take is activating the yeast. You do this by sprinkling it over warm-ish water and waiting a few minutes to make sure it blooms, or poofs up a bit. When it does this, it's a sign that the yeast is still alive and is up to the task of making your bread rise. Many people are more familiar or feel most comfortable with this process because active dry yeast has been around longer than instant yeast. Active dry first came onto the scene in the 1940s. At the time, it completely revolutionized baking. Previously, the only form of yeast available to home bakers was fresh yeast or cake yeast, which is very perishable and must always be refrigerated. With the invent of active dry yeast, bakers now had a shelf stable yeast that lasted more than just a few weeks.

To get down to the nitty gritty differences between types of yeast, a little background on how baker's yeast is commercially produced can be helpful, or at the least, interesting. It's actually a very amazing process to consider. The yeast that you eventually find on that tiny sliver of shelf at the grocery store starts in a laboratory, where a few single, healthy, vigorous cells of yeast are selected to start a batch. They are isolated from the other cells and placed in a sterile test tube, along with any nutrients needed to grow. The cells of yeast in the test tube will then begin to multiply via budding, which is a form of asexual reproduction. These strict growing conditions ensure that only the strain of yeast desired will be produced. If the yeast were not started in a sterile test tube, it would likely be infiltrated by wild yeast that may be residing in the air or surroundings.

Flowchart via Dakota Yeast website

As the cells of yeast continue to multiple, they soon outgrow the test tube and are transferred into flasks and finally large fermentation tanks. The flasks and fermentation tanks contain wort, which is a mixture of minerals, vitamins, and molasses. The wort is food for the yeast and helps it to multiply even faster. The amount of wort fed to the yeast is carefully regulated in order to maximize growth while preventing any alcohol production. As the yeast continues to grow rapidly, it transferred into larger and larger tanks. The final tanks are huge, with capacities of 40,000-60,000 gallons. I can't really visualize a 60,000 gallon tank, but according to Fleischmann's (a large commercial yeast producer), they are as tall as a multiple-story building! As someone who grew up in a farming community, I am picturing a grain elevator full of yeast. Whoa. Another amazing part about this - when the yeast is initially transferred to the final, largest fermentor, it often only fills about a third of the space. The yeast then continues to multiply and will fill the entire fermentor in just 15-20 hours!

Finally, when the point is reached where just a few cells of yeast have multiplied and grown and multiplied and grown to fill the space of a multi-story building, it is ready to be harvested. At this point, the yeast is washed many times and then separated from the leftover growth nutrients through a process called centrifugation. If you're not familiar with this process, it basically means that you put everything in a tube and spin it around really, really fast, so that everything separates out from each other by density. A good visual is to imagine clothes spinning around in a washing machine. Once the yeast has been separated from the nutrient debris, it is in a liquid form known as cream yeast. It is ready for further drying so that it can be processed into one of three final forms: fresh yeast, active dry yeast, or instant yeast.

At this point, I am going to let you take a brain break from thinking about yeast and we will pick up right here in part two of this post. See you in part two, and let me know if you have any questions (I might not have the answer, but I'll definitely listen to the question)!

my favorite brand of yeast...more to come on this!