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What Is Yeast?

What Is Yeast?

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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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Every Question You've Ever Had About Yeast, Answered

Conversion rates, substitutes, sourdough starters&mdasheverything.

All right, folks, let&rsquos talk yeast. In case you hadn't heard, baking has become our new national pastime&mdashor maybe it's been yours all along&mdashand it's led to an onslaught of questions about yeast. Like, what does one do if there's only one kind of yeast at your store and it's not the kind you need? Or worse&mdashwhat if there's no yeast of any kind to be found at all? Is your recipe doomed? And, for those lucky enough to encounter a fully-stocked shop&mdashwhat's the difference between all these different types of yeast?

We're prepped to answer all those questions, but first:

What is active dry yeast?

This partially dehydrated, granular yeast is the more common variety of yeast that you&rsquoll see at the grocery store. Active dry yeast is sold in packets or small jars and provides an airy, light texture, while adding a punch of wheat-y, nutty flavor to whatever it is used to leaven. This shelf stable product was developed by Fleischman&rsquos Company during World War II so that the U.S. Army could make bread without having to refrigerate fresh yeast (which typically lasts in the refrigerator for no more than two weeks).

As any bread pro would tell you, the dormant yeast cells in active dry yeast need to be proofed. In order to do this, you should always dissolve the yeast in lukewarm liquid such as water, milk, or beer (about 110°F), and wait for it to bloom. Bakers typically add sugar or honey at this point as well to feed the yeast.

A thin layer of fuzzy bubbles should form at the top of the liquid after about 5 to 10 minutes, and this is how you know that the yeast is still alive. If it doesn&rsquot bloom, that&rsquos because the yeast has probably expired &mdash remember, active dry yeast should keep at room temperature for about six months on average. Once the yeast has been rehydrated in your proofing process, you'll continue to follow along on your baking recipe to add the rest of your dry and wet ingredients.

Where does it come from?

Like bacteria and other microorganisms, wild yeast live all around you. They live on the surfaces of your home, on your skin, on your fruit and vegetables, in your flour.

Knowing this, you can create an environment that encourages their growth: one that is moist and carbohydrate-rich. Tossing a few pieces of unsulphured dried fruit into a jar and pouring in water does just that. In less than a week, that jar will fizz and bubble with activity, and your yeast water is ready for baking.

While capturing wild yeast for brewing and baking is an age-old practice that spans millennia across cultures, this particular technique of preparing a yeast water starter with fruit, herbs, and other plant matter is rooted in Japanese artisan baking, and popularized by Junko Mine who wrote about her method here.

The Mystery of "YEAST"

Instant Yeasts are Rapid Rise (Fleischmann's), Perfect Rise(Red Star) and Quick Rise (SAF). They're all the same thing.

No rehydration is required of instant yeasts. Fleischmann's says on their web site that RapidRise™ yeast actually loses its fast rising capabilities if dissolved in liquid, and will require two complete rises. I assume that holds true for other instant yeasts.

Active Dry yeast has larger granules and is necessary to dissolve completely for the yeast to work. Therefore, Active Dry works best if dissolved in warm water (100° to 110°F).

One envelope (2-1/4 tsp) of yeast (active dry or instant) can raise 4 cups of flour (or about 1 pound)

Yeast dies at 140 degrees F, so be sure that the liquid you add to your dough is not hot. It should be warm, about 95 - 110 degrees F. Use a thermometer until you remember how warm it should feel and then you can just do it by touch. Mr. Food Science himself, Harold McGee, says that yeast activity is best at 95 degrees F/35 degrees C.

Salt can kill yeast or decrease its effectiveness if it comes in direct contact. For this reason, add the salt in a recipe along with the bulk of the flour, when you add that.

1 envelope of yeast is about 2 -1/4 teaspoons.

You don't have to refrigerate yeast, but if you do, it's better to bring it to room temperature before using.

What is Yeast – How Does Yeast Work

Yeast is a tiny plant-like microorganism that exists all around us – in soil, on plants and even in the air. It has existed for so long, it is referred to as the oldest plant cultivated by man.

How does yeast work?

Yeast works by serving as one of the leavening agents in the process of fermentation, which is essential in the making of bread. The purpose of any leavener is to produce the gas that makes bread rise. Yeast does this by feeding on the sugars in flour, and expelling carbon dioxide in the process. As the yeast feeds on the sugar, it produces carbon dioxide. With no place to go but up, this gas slowly fills the balloon. A very similar process happens as bread rises. Carbon dioxide from yeast fills thousands of balloon-like bubbles in the dough. Once the bread has baked, this is what gives the loaf its airy texture.

Types of Yeast Used In Bread Making

There are two types of dry yeast: Regular Active Dry and Instant Yeast (also known as Fast-Rising, Rapid-Rise, Quick Rise, and/or Bread Machine Yeast). The two types of dry yeast can be used interchangeably. The advantage of the rapid-rise is the rising time is half that of the active dry and it only needs one rising.

You can speed up standard yeast bread recipes by changing the yeast in the recipe. Substitute one package Instant or fast-acting yeast for one package regular active dry yeast. Instant yeast is more finely ground and thus absorbs moisture faster, rapidly converting starch and sugars to carbon dioxide, the tiny bubbles that make the dough expand and stretch.

Active Dry Yeast – Cake Yeast or Compressed Yeast

1 package active dry yeast = about 2 1/4 teaspoons = 1/4 ounce
Active dry yeast has a larger particle size than Instant Active Dry Yeast, making it necessary to proof, usually with water, before using. Recommended water temperatures will vary by manufacturer between 100 degrees to 115 degrees F. as measured with an Instant Read Thermometer.

4 ounce jar active dry yeast = 14 tablespoons

1 (0.6-ounce) cube or cake of compressed yeast or fresh yeast) = 1 package of active dry yeast
Cake yeast (compressed yeast) is considered fresh yeast. It is sold in tiny cakes in the refrigerated section of many supermarkets. Fresh yeast does not keep well it will last about two weeks if refrigerated. It is mainly used by professionals as it is highly perishable and must be used within a short time of opening.

Storage of Active Dry Yeast:

Open Package – Active dry yeast will keep well beyond its expiration date printed on the package for one (1) year if unopened at room temperature. It will keep longer if frozen. Place directly in the freezer in its vacuum sealed container. If frozen, you can use it directly without thawing.

Unopened Package – If opened, active dry yeast will keep 6 months in the refrigerator and 12 months in the freezer. Keep yeast in its original container with the opened flap folded closed in a resealable plastic bag. tored at room temperature and opened without a protective outer container, it loses its power at about 10% per month.

Instant Yeast:

I use Instant Active Dry Yeast in all my breads. I use 1 teaspoon of instant yeast per cup of flour. If the recipe calls for over 3 cups of flour, I still use only 3 teaspoons.

1 envelope or packet of instant yeast = 2 1/4 teaspoons = 1/4 ounce

1 (0.6-ounce) cube or cake of compressed yeast = 1 envelope or packet of instant yeast

Substitution: To substitute instant or bread machine yeast for active dry yeast, use 25% less instant yeast than active dry. See Conversation Measurements below.

Instant or Rapid Rise Yeast does not require warm liquid to be activated. This type of yeast has been genetically engineered from different strains of yeast to produce breads. Rapid rise yeast is also more finely granulated than active dry yeast, so it does not need to be dissolved in water first. It can be added directly to the dry ingredients, making it a popular choice for use with bread machines.

Instant active or rapid rise yeast is added to the dry ingredients. Then, the liquid portion of the recipe’s ingredients, warmed to 120 to 130 degrees F, as measured with an Instant Read Thermometer, are added to make a dough.

When using Instant Active Dry Yeast, the bread recipe only needs one (1) rise. The first rise is replaced by a ten minute rest, and you do not need to “punch the dough down” afterwards. The second rise takes place after the dough has been shaped into a loaf.

It will take approximately one hour in a warm place (longer in the refrigerator as a slow rise) until the dough is just about doubled in bulk.

Storage of Instant Yeast: Instant yeast will keep a year at room temperature if unopened. If opened, it will keep 6 months in the refrigerator and 12 months in the freezer. Keep yeast in its original container with the opened flap folded closed in a resealable plastic bag.

Sourdough Starter:

Sourdoughs were originally produced by wild yeasts. The wild yeasts in the San Francisco area produce a unique flavor in breads. Some sourdoughs are over a hundred years old. The starter (or sometimes called a sponge) is a flour and water mixture that contains the yeast used to rise the bread. You can buy dried versions and then activate them or you can make your own, catching the wild yeasts indigenous to your area.

Or purchase Packaged Sourdough Starter Mix at the grocery store or by mail-order. This is what I originally did many years ago.

Conversion Measurements for Using Different Yeasts in Recipes:

Multiply the amount of instant yeast by 3 for the equivalent amount of fresh yeast.

Multiply the amount of active dry yeast by 2.5 for the equivalent amount of fresh yeast.

Multiply the amount of instant yeast by 1.25 for the equivalent of active dry yeast.

Expiration Date and Testing Yeast:

Expiration Date (printed on the yeast’s package) – Yeast does expire. Yeast will last longer than the date printed on the packet if it is kept in the refrigerator. It will last even longer in the freezer (for up to a year or even more).

Testing Yeast – Sugar is used in testing yeast. To test yeast: Add 1/2 teaspoon of sugar to the yeast when stirring it into the water to dissolve. If it foams and bubbles within 10 minutes, you know the yeast is alive and active.

Measuring Yeast:

You do not need to be exact in measuring yeast. Remember itis going to multiply like crazy anyway. A little less is fine the dough will rise more slowly and may taste better. NOTE: Too much yeast will give an unpleasantly yeasty flavor and aroma.

Check out all of Linda’s Bread Making Hints:

Check out Linda Bread Recipes using the Bread Machine.

What are the different types of yeast called for in recipes?

Yeast is all around us all the time! This very second. A sourdough starter, the foundation of sourdough bread, is made with wild yeast that’s captured from the air, then fed with flour and water (it’s like an ant farm for microorganisms). But commercially made yeast is better for beginners because it’s easier to work with and produces more consistent results.

You’ll see two main types of dry yeast at the grocery store. Active dry yeast, which often comes in flat packs of three, is what we call for in our Shockingly Easy No-Knead Focaccia because it’s the most widely available. The granules are large—they’re actually made up of live yeast cells surrounded by dead cells (that’s right, not all of the cells are alive) and a growth medium. The yeast is most often activated in warm water or milk, sometimes with a source of sugar, before it’s incorporated into the other ingredients. (If you’re confused, just remember: Activate your active dry yeast.) This hydration phase also gives you a chance to make sure that the yeast is alive—more on that below.

The alternative to active dry yeast is instant yeast, which is finer and can be mixed directly into the dry ingredients, no activation necessary. It contains 100-percent living cells, which means that instant yeast is more powerful than active dry. If a recipe calls for active dry yeast but you want to use instant, a good rule of thumb is to decrease the volume by 25% (for example, if a recipe calls for 1 tsp. active dry, use ¾ tsp. instant). Instant yeast also has a longer shelf-life than active dry: It’s often sold in bulk and can be kept in the refrigerator for years! If you bake a lot but can’t find instant yeast in your area, it might be worth it to buy it online.

Harvest the Yeast Around You!

You’ve heard it: Yeast is everywhere in the air. Now you just need to capture it in a medium and cultivate it. That is actually pretty easy if you can manage to keep the growth of bacteria out. This means, working very clean is key.

I will explain two different ways of making yeast, though I have so far only tried one way myself and the other version is the result of some research. What you will not have – and I just mention that so you will not be disappointed – is a nice cube of fresh yeast as some are fortunate to buy at bakeries or even groceries. However, your homemade yeast will be working just as fine!

You can’t control the growth of your wild yeast and there is a chance that with the yeast, some harmful bacteria are growing, too.

If you are pregnant or your immune system is compromised in any way, you should not use homemade yeast.

How To Make Your Own Yeast For Baking Bread

Maybe you were an avid baker before the novel coronavirus outbreak, or perhaps the current social distancing and stay home restrictions have inspired you to take up the hobby for the very first time.

Whatever the reason, we fully support the latest trend of baking your own bread at home. And, since stores everywhere are reportedly running out of yeast, we're here to help.

One of Rach's culinary staff members, Janette Zepeda, is sharing how to make your own yeast at home using a surprising ingredient: raisins!

While Janette says that there are several ways to make your own starter for baking bread, this is the way she was taught in culinary school.

"My husband and I both lived in the Bay Area for about five years, and raisin starter was a big trend," she says.

It's an eight-day process, but it can actually be quite exciting, Janette assures us. (It's the little things! ?) And, of course, you end up with a satisfying (edible!) payout at the end. Plus, the whole point is that we all have newfound free time, so you might as well use it to learn a useful new skill, right?

How To Make Starter

Day 1

To begin, here's what you will need:

  • 1 ¼ cups spring water or filtered water ("Not tap water, because the chlorine will kill the living bacteria you need to make the starter," Janette says.)
  • 1 tablespoon sugar
  • 100 grams (a little over ½ a cup) chopped or whole raisins
  • One quart-sized glass jar
  • Plastic wrap, to cover

Add the water, sugar and raisins to the jar. Cover the jar with plastic wrap, or use a rubber band to keep a coffee filter in place, and leave out at room temperature. Then, you just wait seven days. Trust the process &mdash you don't need to mix, Janette continues.

On day seven, you should see small bubbles and smell a fruity, alcoholic aroma.

On day eight, you'll see larger bubbles and the smell will be stronger. Once this happens, strain the raisin water, discarding the raisins.

Day 8

Here's what you will need:

To your raisin water, add the flour and sugar. Keep in a warm place until it rises &mdash it should double in size &mdash then place in the refrigerator.

"Now, here is the exciting part!" Janette says. You have to keep a starter going &mdash also known as feeding the starter &mdash by following the directions below.

Keep in mind that while you can feed your starter every day, if you are more of a casual baker, once a week is your best bet, according to Janette.

Every time you feed your starter, you want to take it out of the fridge until it's at room temperature. You should also always feed it equal parts flour and water.

How To Feed Your Starter

  1. Take out and discard ¼ cup from your room temperature starter
  2. To the remaining starter, add ⅔ cup lukewarm water and ⅔ cup all-purpose flour
  3. Mix well
  4. Let sit at room temperature until the starter bubbles, then place back in the refrigerator for another week

How To Prep Your Starter For Baking Bread

When you're ready to bake, bring your starter out of the fridge, discard ¼ cup, add water and flour and mix. You'll want to do this every time before you bake, even if you've already fed your starter that week.

Leave it out for 8-12 hours at room temperature until it doubles in size.

"This is usually a good indication that your starter is ready and strong enough to make some delicious bread," Janette says.

How to Use Nutritional Yeast

Because nutritional yeast is high in nutrients, but is still dairy-free and usually gluten-free, it remains a useful and flavorful supplement for people with food allergies or sensitivities, as well as anyone on a restricted diets. It is low in fat and contains no sugar or soy. If you have never eaten nutritional yeast before start small and do your homework. Its high fiber content may cause a tummy rumble (a little goes a long way, regardless).

Stir it into soups and sauces, or blend it into dips, mashed potatoes, and pur cauliflower. Sprinkle it over hot popcorn, pasta, vegetable bowls, and avocado toast, and incorporate it into crisp homemade seed crackers. Toss it over raw sliced tomatoes, and scatter it across your favorite quick pickles. Make it the secret weapon in your mac and no-cheese. And nutritional yeast is close to essential if you would like your new nut cheese project to sing with flavor.


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