What Is Yeast?

Staff Writer
Nature’s little wonder gives us the finer things in life

Yeast — it’s everywhere, and it’s alive. It’s in the air, in our foods, and puts the bubbly in our champagne. Some might even go so far as to say that it’s one of the foundations of civilization — the ancient Egyptians began using yeast to bake bread more than 5,000 years ago, and it was used to make alcoholic beverages many centuries before then. If it weren’t for yeast, we’d all still be eating flatbread, drinking flat beer, and sipping on grape juice. But what is it, exactly? (Photo courtesy of flickr/kpishdadi)

Simply put, yeast is a single-celled life form that takes in starch or sugar, and ferments it, producing carbon dioxide and alcohol in the process. It is this process that gives yeast its leavening properties, and allows us to enjoy a warm, crusty baguette and the buzz from a cold, frosty beer. Yeast thrives in moist, warm environments — between 70 and 115 degrees Fahrenheit — but not too warm, as it begins to die off beyond 120 degrees. Salt also slows down the growth of yeast.

There are two main types of yeast for sale on the market. If you’re making bread, you’ll want to utilize baker’s yeast, which commonly comes in the form of active dry yeast. Sold in ¼-ounce packets, baker’s yeast is a powder consisting of inactive cells, which once rehydrated, begin to metabolize sugar and give off carbon dioxide — which causes bread to rise. Quick-rising varieties can cut baking time in half, and can be used in place of regular dry yeast, as long as rising time is adjusted.

Brewer’s yeasts are primarily used in making beer. They come in different varieties, but they all share one trait — they are non-leavening. They are a good source of B vitamins, and are often added to food products for their nutritional value. (Photo courtesy of flickr/HeadCRasher)

When baking with yeast, it’s important to make sure it’s still alive. Otherwise, you’ll be wasting your time and energy and end up with a baseball bat instead of a baguette. Proof the yeast by dissolving it in warm water (between 105 and 115 degrees) and feed it some sugar. Put it in a warm spot in your kitchen, and come back in about five to 10 minutes. If you get some foaming action, that’s a good sign the yeast is alive and kicking. If not, it’s time to go bug your neighbor.

The best way to store yeast packets is to keep them in a cool, dry place. You can also keep them in the fridge or freezer, but remember to let it sit out for awhile so it can come up to room temperature before proofing. Most yeast packets also have an expiration date, but it’s always good to play it safe and proof anyway.

So don’t forget — next time you bite into a soft, chewy pretzel, chug an ice cold brew with your bratwurst, or sip on a glass of red wine with your grilled steak, it’s all thanks to one of nature’s magical workhorses, yeast.

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