Yeasts are too small to see, yet they have shaped the course of human history since before humans even knew that they existed. Yeasts are single-cell microorganisms (classified as fungi) and have a taste for sugar. They have been silently working alongside us for thousands of years, bubbling in bread dough, brewing beer, and fermenting wine. These microscopic organisms turn everyday ingredients fragrant loaves, frothy pints, and fine vintages, and they’ve done it since the dawn of civilization. From ancient bakeries in Egypt to modern breweries, yeast has been humanity’s invisible partner in creation, flavor, and survival.

Yeasts in nature

There are at least 1500 species of yeasts that are currently recognized and they can be found in nature pretty much everywhere. Plants, leaves, the shells of many cereals, on our bodies, inside our bodies, animals, flowers, fruit, soil – you name it! Different kinds of yeasts have, over time, found their own preferred environment and ideal conditions to thrive in. Some yeasts are more aggressive (like the ones that cause food to spoil or the ones that can cause yeast infections), while many others prefer to live in symbiosis with their host (not causing it/them harm and sometimes even providing health benefits).

Good and bad yeast

With so many different species, it’s no wonder that some are good and some are bad! Good yeasts, typically the ones we are most interested into, include:

• Baker’s yeast, often used as leavening agent for bread and similar and for brewing beer and other alcoholic beverages;
• Brewer’s yeast, which despite belonging to the same species as baker’s yeast, it is a byproduct of brewing. It is also a good source of nutrients, particularly B vitamins;
• Nutritional yeast, which is an inactive form of Saccharomyces cerevisiae known for its nutritional value, including protein and B vitamins;
• Marine yeast, responsible for the production of several compounds beneficial to nature.

On the other hand, Bad yeasts, typically the ones we are most interested in avoiding, include:

• Spoilage yeast, the ones responsible for food going bad;
• Pathogenic yeast, which can be harmful to both humans and animals. These are the ones to blame for yeast infections, for example!

Supporting humanity for millennia

As we said before, yeasts have been living side by side with humanity since long before we knew they existed. The oldest records (possibly as old as 1500BCE) of this ingredient being used for baking comes from Ancient Egypt. We do, however, have evidence that some beer-brewing and bread-making was already happening Sumeria and Babylonia as far as 8000 years ago.

The first physical description of yeasts came “very recently”. It was only in the 17th century that Anton van Leeuwenhoek, a Dutch Optician, became “the father of microbiology” by observing bacteria through a microscope for the first time. However, the word “yeast” didn’t exist until two centuries later, when the fermentation process started being studied more. It was only in 1857 that Louis Pasteur, a French Chemist and Microbiologist, was able to prove that yeasts are specifically responsible for the fermentation process – consuming sugars to feed and reproduce and producing alcohol and carbon dioxide as a byproduct.

Recipes with yeast

There are plenty of recipes involving yeast somewhere in the process! A nice and crunchy loaf of bread with a soft heart? Check. A mouth-watering rosemary-topped focaccia? Check. A refreshing apple cider?Check. Flatbread? Check, and yes, even the dough for flatbread needs to rise!

There is really plenty to go around and I really can’t list it all, but if this made you even a little curious to try out the magic of yeast for yourself, why not start from one of my recipes? Whether it is to make your own yeast or a delicious homemade pizza, try picking one from below!