Yeast: Everything you should know


A conspicuous fact about baking is that part of it involves a key ingredient “yeast”. We have seen numerous processes utilizing the physiological properties of this tiny microscopic egg shaped fungus from bread baking, beer brewing to even wine production. But what makes yeast so important? What role does it play in bread baking? What benefit food-wise does this microbe “yeast” which has been a focus of study for several years with over 50,000 published write-ups worldwide have? Hopefully, your boring days of unimaginably toilsome dreams with those pee-wee microbes are over and finally going to get answers to some if not all of your questions.

What exactly is yeast?

  • Yeast are microbes of the fungus kingdom originating hundreds of millions of years ago with over 600 species identified. Each Specie could have thousands of strains, performing different functions and even look different.
  • Yes, they are living things that grow, respire, reproduce and feed just like you do. Their feeding process which makes bread dough rise is enough evidence for that.

Are they harmful?

Just like there are good and bad humans, there are also good and bad yeast! From oral to vaginal infections in humans, this microbe is responsible for a fungal disease common to about a million HIV & AIDS patients causing at least 600,000 deaths yearly according to Wikipedia. They are also accountable for food spoilage worldwide.
  • Another question you might be interested in is whether or not “Active raw dry yeast is edible?” No. The only form available for human consumption is the nutritional yeast and that is because it has been deactivated. The reason why any other form shouldn't be consumed is because to some extent it can survive in the stomach, and because it can react and convert food and fermentable sugars present in the stomach to carbon dioxide (CO2), consuming a large amount of active raw yeast could lead to a heavy concentration of CO2 in the stomach. “As if its presence in earth with a volume approximately 25 septillion times greater than that of a fully expanded stomach poses not enough threat” That doesn't really mean you’ll die when you consume it, as a matter of fact, acids in the body eventually will neutralise and render them harmless in the body. The biggest threat would be consuming yeast when you are “Yeast allergic”.
In addition, naturally occurring yeast can be found on the skin of fruits and berries such as apples, peaches or even grapes. With confidence I can say that the vast and important benefits of yeast makes it the heart and soul of bread baking.

Why is Yeast important in baking?

Yeasts are biological leavening agents, which means they can cast foaming actions (release of gases like CO2 or H2) that lightens, expands and softens the medium they are in (mostly dough). Some brilliant result of this action are breads, French brioche, Nigerian masa, bons, rolls, excreta. Majority of yeast recipes are soft, light, well- risen and most of all have a spongy texture.
What happens in bread dough is similar to that of an inflated balloon where air expands the balloon because it has nowhere to flow and finally explodes if elastic limit is reached. Bread Flour (High protein flour) contains two major protein Gliadin and Glutenin that change shape and bond together (in a molecular sense) to form an elastic network of proteins called gluten (dough in general) in the presence of water.
This gluten has the ability to trap in air, expand and explode much like a balloon. Because doughs are generally covered with starch after kneading, you’ll have to wash them in water to see a real picture of gluten. Doughs are rich in fermentable sugars.
Now when yeast is added to the dough mixture (flour and water),
  • It breaks down fermentable sugars present in the dough into a gas CO2 and ethanol. The gas released inflates the dough with bubbles and the dough rises to become soft and light, giving a spongy texture to the dough. How far the dough stretches depends on the strength of the gluten network which in turn depends on how well you knead the dough.
In short, this fungus is important in baking because it serves as leavening agents, agents for strengthening gluten network, and aid the formation of well-risen, good-looking, puffy recipes!

What other processes apart from baking are they used?

Aside baking, there are numerous processes utilizing the useful physiological properties of this fungus. The most important ones include
  • Beer Brewing
  • Production of wine
  • Topping for pasta dish, breads or rice cakes, popcorn, salads, or even in soups (in its deactivated form)
  • Treatment of hair, skin etc.

What is a perfect substitute for it?

Sincerely speaking, Yeast has no ideal substitute and that is because there are some properties that can only be found in it. However there are processes/recipes involving numerous ingredients that can make you partial substitute for it. Also its alternatives could be baking soda or baking powder.

How long do yeast-baked products last?

“How long do yeast baked products last” is a question that depends on “preservation and ingredients”. Since different products include different ingredients, I can generally say that yeast baked products without preservation can last from a few hours to a couple of weeks.

Forms of yeast

Fallaciously speaking they exist in two basic types, they are:
  1. Baker’s yeast: A general class for all yeast used during baking process. They are available in different forms which include
  • Deactivated: Simply dead yeast with no leavening properties, mainly used to increase the extensibility of dough I.e. pizza or sometimes consumed.
  • Nutritional: It is a form of deactivated yeast known for its significant source of some vitamin B-complex. It is sold commercially as a food product.
  • Active dry: A form that is temporarily deactivated, and requires activation before use. Method of deactivation involves coating yeast cells with dry dead cells with some growth medium. It is available in different brands
  • Instant: Much like the “active dry” but has smaller granules, and does not require activation before use. It is available in different brands
  • Rapid-rise: A form of instant yeast with smaller granule size, which dissolves faster and expels larger amount of CO2 more that any yeast hence resulting to a faster rise of dough as the name implies. It is available in different brands.
To learn about different types of yeast, when and how to use them, check this article “”
2.  Brewing Yeast: A general class for all yeast used during brewing process. They include
  • Top-fermenting: Also known as Ale, are yeast that prefer to rise to the surface of the fermenter during fermentation. They are most active at temperatures ranging from 10 to 25 degrees Celsius. Some styles made from ale are stouts, wheat beers, altbier and so much more
  • Bottom-fermenting: Also known as larger yeast, are those that prefer to settle at the bottom of the fermenter during fermentation. They are most active at temperature ranging from 7-15 degrees Celsius. Some styles made from them are American Malt liquors, Bocks, Pilsners and so much more.
These microbes are halfway responsible for the flavour and aroma of the beer, and leave by-products of flavour compounds during fermentation process.

Using baking powder, baking soda and yeast together?

There are very few recipes that make use of both baking powder or baking soda and yeast together. Yeast is slower than baking powder when it comes to leavening action, but in nutrition and flavour it comes first. So I think a proper combination of both could yield a well-risen recipe with a balanced nutrition and flavour in the quickest amount of time. A balanced combination of baking soda (small amount) in a yeast dough could enhance rise, whereas a heavier amount could rise the dough too quickly for it to support the gases, eventually degassing. So instead of having something that is well-risen, airy and light you could end up with something that is too dense. In addition, you can always test to see whether or not a recipe concords with both (in varying amounts). Left to me, I would use yeast or chemical leaveners, but not both.
baking powder and yeast

Some Interesting facts about yeasts

  • It was for long considered to be globular structure rather than living organism.
  • It is evolutionally diverse with different types performing different functions.
  • The word itself “yeast” means to bubble, boil or foam.
  • It is a very slow leavening agent. Yes, slower than baking powder and baking soda.
  • It can be accountable for the flavour and aroma in beers.
  • Strains of some of its species produce killer toxins which are used in treating yeast infections.
  • It can compete with each other.
  • It is everywhere.
  • It reproduce at very fast rate thousands of new cells, especially at lukewarm temperatures.

In conclusion

Yeasts has played a major role in the food industry for quite some years now. The very useful nutritional, baking, brewing and even healing properties embedded in it makes it almost irreplaceable in all respect. In addition to that, it shouldn't also be forgotten that this so called “useful microbe” was and is continually responsible for thousands of deaths and infections in humans worldwide.

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