How to activate fresh yeast

Posted on Last updated: December 27, 2020 Categories Cooking School

If you want to bake with confidence, learning how to activate yeast is the first step. For some reason, this terrifies about 99% of the people I know. Not just the activating, but the rising, kneading and baking that usually comes with it. But baking soft cinnamon rolls or a loaf of homemade bread won’t happen without it. This the part you don’t want to miss–let me show you how easy it is!

How to activate fresh yeast

Maybe you’ve heard or lived the horror stories of trying to bake with yeast. You didn’t make bread. You made hockey pucks.

You didn’t make cinnamon rolls, you made petrified stone for your flower bed. Flat, hard, dry stuff that just didn’t do what you thought it would. What went wrong? It was something with your yeast which works as the leavening agent (the thing that makes bread rise).

There are only two things you can do to yeast: 1) not wake it up or 2) kill it. Both of which will make your bread flatter than a flitter. Because we all have absolutely no idea what a flitter is, but it sounds good.

Where do I get yeast?

You’ll find yeast in the baking aisle near the flour. It’s sold in a jar (way too much for most people to use) or in a three pack strip. Simply cut one or two packets from the strip to use as your recipe states. Each packet is about 2 1/4 teaspoons of the jarred kind.

Is there more than one kind of yeast?

Yep. You’ll probably see “fast acting” (sometimes called Rapid Rise) and regular. I just use regular. You aren’t going to save any time with the rapid rise kind really. There’s also fresh yeast, but it’s harder to find and not worth talking about right now.

Before you activate yeast

Before you properly activate your yeast with my method, do me a favor and check the expiration date on the package. Flip over the strip and make sure it’s still in date. Even if it expires that month, you should be fine. Just don’t use it if it’s out dated. It’s probably useless and there’s no point in risking in.

How to activate yeast step 1: Warm water

This is the part that usually gets people, but it’s easy. Yeast needs warm water to activate. How warm? Experts say about 110 degrees but who’s checking that? Here’s how I do it: run some tap water until it’s warm. Not hot. Just warm. Now bump the faucet till you can say “Well, that’s definitely hotter than warm. Not so hot I want to wash dishes in it or anything, but hot enough.”

That’s the temperature you want. Fill your cup with the amount of water called for in the recipe (usually a cup) and sprinkle your packet of yeast over the top of the water. You don’t even need to stir it in. That’s what I did in this picture:

How to activate fresh yeast

How to activate yeast step 2: Add a little sugar

Once you get the yeast on the water, add about a teaspoon of granulated sugar. Yeast is fed by sugar and this will help it multiply and activate with a little snack in its belly. Basically it speeds up the process.

Drop in the sugar and give it a stir with a spoon. After a couple of minutes it will start to look cloudy and have a little bit of foam on top. Be patient. The time is not yet! It looks like this:

How to activate fresh yeast

How to activate yeast step 3: Give it time

Depending on how warm your house is and how warm your water is, this step may take longer for some people. TV people say “five minutes” until your yeast starts to foam, but in my house where it’s cool right now, this step can take up to 15 minutes.

Sometimes I just stand there and watch my yeast like a nut case waiting to see something bubble to the top (and it will). When I see that, I just go ahead and throw it in my dough. But if you want to be totally sure, wait for this kind of foam or activity in the cup:

How to activate fresh yeast

Once you see the foam, you’re ready to use your yeast in any recipe it calls for. If you DON’T see foam and you’ve been patient (given it 15 minutes or so), try again with another packet. If you made your water hot, try reducing that heat a bit and give it another try.

Just don’t go on and put it in your recipe like that. Lord knows nobody wants to waste hours baking something that is dead on arrival.

Still have questions? Watch me here:

Are you ready to bake? I knew it. ?

Still have questions about how to activate yeast or anything on this topic? Comment below and let me know–I’m glad to help!

Yeast is a single-celled organism classified in the kingdom Fungi, and requires moisture, oxygen, food, and appropriate temperatures in order to survive. Under these suitable conditions, the yeast will reproduce and generate alcoholic fermentation. During fermentation, yeast and bacteria consume sugars, and the resulting products are alcohol and carbon dioxide.

Generally speaking, bread dough is an ideal environment for the yeast, providing all the necessary conditions for its needs.

  • Water is needed by the yeast, since the semipermeable yeast cell wall can only absorb small molecule nutrients in a dissolved state. It is well known by bakers that salt retards the activity of yeast fermentation, due to osmotic pressure exerted on the yeast cells by the salt. Salt, being hygroscopic (attracting moisture), draws water out of the yeast cell, reducing the amount available to the yeast, and this is why there is a decrease in fermentation from the presence of salt. Sugar acts the same way. It too is hygroscopic, and once a dough contains more than 10% sugar, a decrease is noted in the rate of fermentation.
  • Oxygen, obtained mostly by the mixing of the dough, enables the yeast to metabolize nutrients and to multiply. Although yeast requires oxygen for its reproduction, in reality there is almost no reproduction occurring in bread dough, and the rise we see is almost entirely due to gas production during fermentation. Available oxygen is used up within a matter of minutes after dough mixing, and fermentation occurs in an anaerobic environment.
  • Dough temperature is crucial for yeast activity. For commercial yeast, the optimum temperature for fermentation is 86° to 95°F or even higher. It is important to note, however, that a dough temperature in this range is inappropriate; although fermentation would be favored, it would occur at the expense of flavor development, which requires lower temperatures. Wild yeasts prefer a narrower temperature zone than commercial yeast, and in general perform better at slightly lower temperatures than commercial yeast.

During fermentation, food is provided to the yeast by the conversion of starches (by amylase enzymes) into sugar. The yeast ferments the sugar, and as a result of this fermentation, carbon dioxide gas and alcohol are produced. The CO2 is trapped by the gluten network in the dough, and provides volume to the baked loaf. The alcohol is largely evaporated during the baking of the bread. Another by-product of fermentation is heat.

Kinds of yeast

In nature, there are dozens of genera of yeast, hundreds of species, and thousands of subspecies or strains. Saccharomyces cerevisiae is the strain that has been chosen for commercial yeast, because it has characteristics that favor rapid gas production. Commercial yeast is available in a number of forms, from cream yeast (a liquid form of compressed yeast, it is usually delivered in tank trucks to storage bins, and is used in very large operations), to compressed yeast (also called cake yeast or fresh yeast), and finally, active dry yeast and instant yeast. There is also osmotolerant yeast, which is designed for enriched formulas with less water.

Conversions

When converting from fresh yeast to dry yeast, it is important to adjust the weight of the yeast. Although it is best to follow the conversion ratio provided by the manufacturer, there are general conversion guidelines that may prove helpful.

  • To convert from fresh yeast to active dry yeast, multiply the fresh quantity by 0.4. Active dry yeast must be hydrated in warm water before being incorporated into a dough.
  • To convert from fresh yeast to instant dry yeast, multiply the fresh quantity by 0.33. Instant yeast can be incorporated into the dough without first rehydrating it; however, it is sensitive to ice or ice-cold temperatures, and if the water temperature of the dough is cold, it is best to mix the dough for a minute or two before adding the yeast. In order to maintain dough yield, most manufacturers suggest making up the weight difference between dry yeast and fresh with additional water.

A symbiotic relationship

There is an interesting relationship in what we call San Francisco Sourdough between the wild yeast, Candida milleri, and the dominant lactobacillus strain, Lactobacillus sanfranciscensis. C. milleri cannot utilize maltose during fermentation, while Lb. sanfranciscensis is happy to use it. And once it does, it excretes glucose. This is fortunate for C. milleri, because it is fond of glucose, and ferments this simple sugar readily. At the same time, competing bacterial species are inhibited by the presence of so much glucose, and this is to the benefit of Lb. sanfranciscensis, whose development is therefore favored. A last factor in this relationship pertains to acidity. Lb. sanfranciscensis produces a lot of acetic acid, which contributes significantly to the flavor we associate with sourdough bread. C. milleri is more tolerant of an acidic environment than many yeast varieties. The high level of acidity prevents competing yeasts from dominating the culture, much to the benefit of C. milleri.

How to activate fresh yeast

Savvy bakers regard fresh yeast as the best over its dry counterpart. There is, however, a high chance that it will go bad if it is not stored correctly.

While freezing the yeast will make it last longer, if it is not stored under the right conditions before that, it may turn bad or dry out.

So first and foremost, it is essential to note the right way to store fresh yeast. Believe it or not, yeast is made up of living cells, and the key to preserving it is making sure that you never expose it to air and moisture.

So, always make sure that your yeast is sealed tightly in a container. Afterward, you can choose to keep it in the fridge or freezer.

When kept in the fridge, fresh yeast typically keeps for two weeks. When stored in the freezer, it keeps for much longer – 3 months or more.

How to activate fresh yeast

If you chose the freezer, here’s a step-by-step guide on the best way to:

First, don’t just stick the yeast in the freezer right away. Place it in the fridge for at least 12 hours. If you are yet to open the yeast, leave it in its original package. This is the best protector. If you prefer to divide the blocks of fresh yeast into smaller portions, cut them as you want then, wrap each part in cling film then again in aluminum foil. Get a resealable plastic bag and put all the cut blocks of yeast inside. Squeeze the air out; remember that fresh yeast should never be exposed to air! Finally, seal the bag and place it in the freezer.

A crucial thing to note is that the way you seal your yeast determines whether it dries out or not. It should never dry out!

This is why you are prompted to keep the fresh yeast in many layers of covering. This makes sure that it remains moist for use no matter when you take it out.

If it does dry out, it becomes utterly useless!

If you want, you can proof your fresh yeast before freezing; here’s how to:

Add the perfect amount of warm water into the yeast, mix them. Add sugar into the mix and let stand for 5 to 10 minutes. The mixture should be bubbly and expanding; otherwise, the yeast has gone bad.

by Jen Evansy · May 30, 2020

Fresh yeast, also called baker’s yeast, is hardly seen anymore except in professional bakeries. When in stock, you can find it in the dairy section of the supermarket. Fresh yeast is compressed, and it looks like a small block wrapped in foil.

With this type of yeast, the freshness is the key. So, before purchasing, check the expiration date so that you always grab the freshest batch.

Keep in mind that the older the yeast, the longer it will take to rise, and it is always best to use it before the expiration date. If you don’t store it right, fresh yeast can ‘go off’ (die) quite fast, rendering it completely useless.

Yeast that is just purchased and fresh will always give you the best results from my own experience.

However, if you wish to store it for later, here are some useful tips and tricks on how to do it to keep it alive as long as possible.

How To Keep Fresh Yeast Alive Longer?

How to activate fresh yeast

Fresh yeast has no artificial additives, and it is highly perishable. It should be stored in the fridge at a temperature of 40° F (4° C) to make it dormant and keep it alive longer. When kept in a cool place, fresh yeast will last up to 4-6 weeks.

Just make sure that it is kept away from the door or areas of the fridge that regularly experience temperature shifts.

Unlike dry yeast, I don’t generally recommend freezing fresh yeast due to some risk of harming it. But, if you wish to freeze it, following the steps below will give you a better chance of keeping it alive and active.

How To Freeze Fresh Yeast?

Fresh yeast should be used within 4-6 weeks when kept in the fridge. For long term storage, it is best to freeze it within two days after purchasing. It’s best to store it at the back of the freezer, away from drafts and limiting exposure to temperature change.

When storing fresh yeast, wrap it very well – heat and air are your enemies! Makes sure that it remains moist. Once it dries out, it becomes useless.

Steps for storing it in the freezer:

  1. For long-term storage, freeze it within two days of buying it for the best results.
  2. Portion it out to little blocks or cubes so you can thaw only what you need later.
  3. Wrap it airtight, in foil or plastic wrap.
  4. Place the yeast in a saleable freezer bag or an airtight container or a zipper freezer bag.
  5. Store it at the back of the freezer.
  6. Prior to use, take it out of the freezer the night before and place it in the fridge to thaw. Do not defrost it at room temperature.
  7. Proof it before use.

Here is another way you can freeze it:

  • Crumble the yeast into fine grains and mix with flour in a 1:2 ratio.
  • Separate 46g into small Ziploc bags with the air pressed out.
  • Store in an airtight container and unthaw one bag for a loaf.

How Do I Know If The Yeast Is Still Good?

It is simple to check if your fresh yeast is still good for baking. Look at the color; it should be ivory, off-white color throughout. Check the consistency. It should be moist, but crumbly with no noticeable hard spots.

If there are discolored darker spots or the consistency is dry and hard, then you need to throw out that batch and buy a new one before baking. If you feel that it is still good, then proof it/test it to make sure the yeast is alive.

How To Proof Fresh Yeast?

  1. Take 1 teaspoon of sugar and one ice cube-sized piece of fresh yeast.
  2. Crumble the yeast in a small bowl or a cup, add the sugar, and one tablespoon of warm water no hotter than 100° F (40° C).
  3. Mix them all together until it is a paste consistency.
  4. Let it sit for 10 minutes.
  5. After about 5-10 minutes, the yeast will begin foam on the surface. That foam means the yeast is alive.

Now, you can proceed with your recipe and mix flour and other dry ingredients. However, if there is no foam, the yeast is dead and not suitable for baking.

You can also use this method to test active dry yeast.

Read also: Is your dough not rising in the bread machine? Try this yeast instead, it will work every time. Read more.

Is Fresh Yeast Better Than Dry One?

How to activate fresh yeast

Professional bakers use fresh yeast because they say it has superior quality and slightly sweeter taste compared to dry versions. Although it is more expensive and harder to find than dry yeast, it is recommended for bread recipes that require a slow and long rising time, as it stays active for longer.

Also, some people claim that bread tastes better has perfect puff and texture with fresh yeast compared to using dried one.

How Much Fresh Yeast For 7g Of Dried Yeast?

How to activate fresh yeast

Now, if you want to try out fresh yeast to see if it really is better but the recipe calls for dry yeast, what do you do?

Don’t worry, you can substitute one type for another, but the quantities need to be adjusted. Remember, it is not an exact science; few grams more or less won’t make much difference in your recipe.

To get the required amount of fresh yeast is multiplying it by 3. One sachet of 7 grams dried yeast (7.39 ml, 0.25 oz, or 2 teaspoons) multiplied by 3 equals 21 grams of fresh yeast.

Another good way to remember the conversion is:

From Dry to Fresh – 1 teaspoon (3.5 grams) dry yeast equals 10g of the fresh one.

Because fresh yeast has about 60-70% moisture in it, that is the reason you need to use a lot more of it compared to the try one.

Quick Summary

You must proof fresh yeast before adding it to your bread. If the recipe you are following does not give measurements for fresh yeast, then you can use our handy conversion guide to help you. Storing it in a cold, dry place is very important, and once opened, store it in an airtight container in the fridge or a freezer.

Do you want to master the art of bread baking? Check out my secret list of best bread baking blogs here.

About Jen Evansy

Nutritionist, researcher, and writer, interested in everything nutrition and food-related. Striving to inform, encourage, and inspire all the readers to make healthy and informed choices when it comes to cooking, food, diet, and nutrition.

How to activate fresh yeast

When you’re searching for a recipe to bake, cake or bread and you finally come up with a recipe you want, don’t you have the feeling that whatever yeast the recipe deems, you just have the other kind? if so, fresh yeast vs. dry yeast article is just for you.

First let’s make some order in this mess, we have 3 kind of popular yeast in the market, fresh yeast that look like a sponge or small cake, active dry yeast and instant yeast (also known as rapid rise yeast). Here’s a spoiler, there are all just as good and will do the job however quantities and time frames are different, so certain recipes can ask for a different kind of yeast, in 99% of the cases, you can replace the recipe yeast with what you have at home, but pay attention to time frames and conversion quantities of fresh Yeast vs. Dry yeast, I’ll mention in this article.

Fresh Yeast

Soft and solid beige color yeast with 70% moisture, it is also known as cake yeast or compressed yeast.

Fresh yeast has a short-term shelf life, 3-4 weeks in a regular fridge, this makes them unavailable in many stores and a must to use within a certain time frame.

Fresh yeast can be added directly to the dry ingredients by small chunks or added to warm water with sugar or honey to wake them up and afterwards added to the dough.

Active dry yeast

The most popular yeast in use today, it looks as a fairly big granule of yeast in a gray brownish color.

Active dry yeast can be stored in the fridge for 2 years or in the freezer for a decade, which makes this kind of yeast very comfortable yeast type for the home amature baker.

Active dry yeast needs to be dissolved in water before used in a recipe.

Instant Yeast

Another kind of the dry yeast family, these yeast are processed much like the active dry yeast however they are milled into finer granules. The result of this is that they are absorbed in the dough much more quickly and does not needed to be dissolved in water, just add them to the dry ingredients.

Instant yeast are added with enzymes that makes the dough proof faster and in an efficient way that according to the manufacturers, when making a bread we can skip the second proofing and just shape the loaves after the first one.

My personal opinion is that Instant yeast can be used Only for bread machines loaves and not when making regular bread, it can be suitable for pound cakes as well.

Fresh yeast to dry yeast conversion

I read a lot of different conversions regarding fresh-dry yeast conversion however it is quite simple, the formula is just multiply or divide the quantities by 3.

1 gram of dry yeast = 3 grams of fresh yeast, so if a recipe deeps for 10 grams of dry yeast we need to use 30 grams of fresh yeast.

You can remember this in another way, 10 grams of fresh yeast = 1 teaspoon of dry yeast (3.3 grams).

Fresh Yeast vs. Dry Yeast – which one to use?

I’m sure anyone who reads professional baking literature will say that fresh yeast are superior to dry yeast, I respect this opinion since many professional bakers are working with fresh yeast however for the weekly home baker the difference is little and hardly noticeable.

One claim is that fresh yeast just taste better when making bread, I agree with that claim however the difference is very small, not worth going to a grocery store 30 minutes from your house especially to buy fresh yeast.

Another claim is that the fresh yeast proof the dough faster and more efficient, this might be true in some cases since dry yeast have a percentage of dead cells that will not proof the dough so in fact you are using less yeast than the dough requires, but other than I see no difference.

At the end of the day, it all depends on what you’re trying to make, for breads I would consider to use the fresh yeast if you have it at home but I wouldn’t bother in using them on cakes, just use the active dry yeast, one thing is certain, avoid from the rapid rise yeast unless you’re in a hurry, always remember, proofing is not just giving the dough its size, it is a heavy enzyme activity that requires time and time equals to flavor, shortening this procedure will resolve in a flat pale taste.

How to activate fresh yeast

How do I know if my yeast is still active? The common method is proofing it. Unfortunately, people often make mistakes proofing it. We’ll explain how to properly test yeast and mistakes people make that kill it.

Dry yeast is hibernating. It has to be activated to prove that it is still active and capable of creating the airy loafs we expect when baking bread.

You can activate the yeast to get the desired effect while baking, and you can “proof” the yeast to verify it is working before you add it to the bread dough.

You were by definition proving that the yeast was good.

This article may contain affiliate links. As an Amazon Associate, I earn from qualifying purchases. Please take that into account.

Extra (nice to have):

  • Kitchen scale
  • Dough scraper and bowl scraper (yes, they are different)
  • Cooling rack
  • Baking stone (you don’t need a dutch oven if you use this)

?Learn how to make bread and pizza with this awesome book.

How do you activate yeast?

You should mix in a small amount of warm water into the yeast to activate it. Don’t use boiling water – that will kill it. Note that water too cold will fail to activate the yeast, too. If you use cold tap water, the yeast won’t activate.

Give the yeast a minute or two to sit at room temperature before you mix the water into the yeast. Gently do so until the yeast is dissolved in the water. Don’t add more water to activate the yeast than the recipe calls for, or you’ll reduce the yeast’s effectiveness.

Do I have to activate all types of yeast?

No. It isn’t necessary to activate instant yeast, only active dry yeast. Instant yeast can just be mixed in with the dry ingredients. You’ll know if that yeast is inactive if it fails to work. If the yeast “proofs”, then you know it is good.

What is proofing the yeast?

Proofing the yeast is when you let it metabolize the sugar and propagate. This takes at least a minute or two, but it can take up to ten minutes.

If it generates an airy foam, you know it is working properly. It is at this point you can add the yeast solution to the rest of the recipe.

Why do people proof yeast?

It can take hours to make a loaf of bread. You don’t want to waste your time by adding dead yeast to it. You can eat the accidental flatbread, but that will fall short because it wasn’t what you were planning on making.

Do I have to add sugar and salt to activate the yeast?

You can add a pinch of sugar to help activate the yeast. Do not add salt to the yeast at this stage, or you risk killing it.

If you don’t have sugar, you can add a pinch of flour to help feed the yeast. Don’t add sugar substitutes, since this won’t nourish the yeast and could kill it. The yeast needs a food source like sugar to grow.

What is the right way to proof yeast?

If you have a quarter ounce packet of yeast, you prove the yeast is alive by adding it to a quarter cup of warm water. Warm up the water before you add the yeast so you don’t kill the yeast by adding heat to the water while the yeast is in it.

Once you add the yeast, add a teaspoon of sugar or molasses. Within ten minutes, the mix should be bubbling or foaming. This proves the yeast is alive.

You can add this mixture to your recipe. Just reduce the water that needs to be added by the quarter cup of water you used in the proofing process.

How else can I determine if yeast is stale?

One way to determine if yeast is stale is to sprinkle a little over warm water. This water needs to be warm enough to activate it but not hot enough to kill it. Sprinkle some sugar over the yeast.

Don’t mix the sugar with the yeast. Cover the container and wait ten minutes. When you uncover it, active yeast will create bubbles in the water. If the yeast is stale and dead, the yeast will sink to the bottom of the container.

I proofed my yeast but the bread didn’t rise. What happened?

The yeast needs the right environment to do its work. If you didn’t give the bread dough enough time to rise, it won’t be as fluffy as expected. The dough needs an hour or two to rise.

And fast-acting yeast won’t change this time frame very much. If you didn’t mix or knead the dough sufficiently, you won’t move the yeast around enough to get the light, airy loaf you expected.

Does the expiration date tell me when the yeast is dead?

Yeast isn’t like eggs or sugar. It won’t go bad. It will just die. If the yeast is well past its expiration date, it is probably dead. However, freezing yeast will make it last almost indefinitely. In this case, you’ll restart the clock when you thaw out the yeast.

What if the yeast is only partially active?

Yeast is a living organism. If it starts to bubble when you “proof” it but not as much as you expect, feed it some sugar and wait. The surviving yeast will multiply. After all, that’s what it will do once it is mixed in with the bread.

If the yeast is close to expiring or you used water near the 110 degrees Fahrenheit limit, you may have to wait twenty minutes for the surviving yeast to create a frothy mix. Once you have a good froth, mix the yeast in with the dough.

If you don’t see any foam, add another packet of water to the mix and see what happens.

Why might the bread fail to rise like expected?

One possibility is that the yeast is dead. That’s why people “proof” or prove the yeast is good before mixing it into the rest of the ingredients.

If the yeast was killed during the mixing process, such as when you add salt right after adding the yeast, that will prevent the yeast from causing the bread to rise.

Not giving the yeast enough food or time to work can make it seem like the yeast is dead.

If the bread dough isn’t protected from drafts and kept at the right temperature for the one to two hours it needs to rise, which can prevent the bread from rising as much as you expected.

Yeast is a single-celled organism classified in the kingdom Fungi, and requires moisture, oxygen, food, and appropriate temperatures in order to survive. Under these suitable conditions, the yeast will reproduce and generate alcoholic fermentation. During fermentation, yeast and bacteria consume sugars, and the resulting products are alcohol and carbon dioxide.

Generally speaking, bread dough is an ideal environment for the yeast, providing all the necessary conditions for its needs.

  • Water is needed by the yeast, since the semipermeable yeast cell wall can only absorb small molecule nutrients in a dissolved state. It is well known by bakers that salt retards the activity of yeast fermentation, due to osmotic pressure exerted on the yeast cells by the salt. Salt, being hygroscopic (attracting moisture), draws water out of the yeast cell, reducing the amount available to the yeast, and this is why there is a decrease in fermentation from the presence of salt. Sugar acts the same way. It too is hygroscopic, and once a dough contains more than 10% sugar, a decrease is noted in the rate of fermentation.
  • Oxygen, obtained mostly by the mixing of the dough, enables the yeast to metabolize nutrients and to multiply. Although yeast requires oxygen for its reproduction, in reality there is almost no reproduction occurring in bread dough, and the rise we see is almost entirely due to gas production during fermentation. Available oxygen is used up within a matter of minutes after dough mixing, and fermentation occurs in an anaerobic environment.
  • Dough temperature is crucial for yeast activity. For commercial yeast, the optimum temperature for fermentation is 86° to 95°F or even higher. It is important to note, however, that a dough temperature in this range is inappropriate; although fermentation would be favored, it would occur at the expense of flavor development, which requires lower temperatures. Wild yeasts prefer a narrower temperature zone than commercial yeast, and in general perform better at slightly lower temperatures than commercial yeast.

During fermentation, food is provided to the yeast by the conversion of starches (by amylase enzymes) into sugar. The yeast ferments the sugar, and as a result of this fermentation, carbon dioxide gas and alcohol are produced. The CO2 is trapped by the gluten network in the dough, and provides volume to the baked loaf. The alcohol is largely evaporated during the baking of the bread. Another by-product of fermentation is heat.

Kinds of yeast

In nature, there are dozens of genera of yeast, hundreds of species, and thousands of subspecies or strains. Saccharomyces cerevisiae is the strain that has been chosen for commercial yeast, because it has characteristics that favor rapid gas production. Commercial yeast is available in a number of forms, from cream yeast (a liquid form of compressed yeast, it is usually delivered in tank trucks to storage bins, and is used in very large operations), to compressed yeast (also called cake yeast or fresh yeast), and finally, active dry yeast and instant yeast. There is also osmotolerant yeast, which is designed for enriched formulas with less water.

Conversions

When converting from fresh yeast to dry yeast, it is important to adjust the weight of the yeast. Although it is best to follow the conversion ratio provided by the manufacturer, there are general conversion guidelines that may prove helpful.

  • To convert from fresh yeast to active dry yeast, multiply the fresh quantity by 0.4. Active dry yeast must be hydrated in warm water before being incorporated into a dough.
  • To convert from fresh yeast to instant dry yeast, multiply the fresh quantity by 0.33. Instant yeast can be incorporated into the dough without first rehydrating it; however, it is sensitive to ice or ice-cold temperatures, and if the water temperature of the dough is cold, it is best to mix the dough for a minute or two before adding the yeast. In order to maintain dough yield, most manufacturers suggest making up the weight difference between dry yeast and fresh with additional water.

A symbiotic relationship

There is an interesting relationship in what we call San Francisco Sourdough between the wild yeast, Candida milleri, and the dominant lactobacillus strain, Lactobacillus sanfranciscensis. C. milleri cannot utilize maltose during fermentation, while Lb. sanfranciscensis is happy to use it. And once it does, it excretes glucose. This is fortunate for C. milleri, because it is fond of glucose, and ferments this simple sugar readily. At the same time, competing bacterial species are inhibited by the presence of so much glucose, and this is to the benefit of Lb. sanfranciscensis, whose development is therefore favored. A last factor in this relationship pertains to acidity. Lb. sanfranciscensis produces a lot of acetic acid, which contributes significantly to the flavor we associate with sourdough bread. C. milleri is more tolerant of an acidic environment than many yeast varieties. The high level of acidity prevents competing yeasts from dominating the culture, much to the benefit of C. milleri.

How to activate fresh yeast

When baking bread or certain cakes, recipes will call for a certain amount of yeast—but it may not be the type you have in the pantry. Yeast comes in two forms: fresh, as compressed cakes or blocks, and dry, which is in the form of dehydrated granules. The dry yeast is sold in a few different varieties, including instant, bread machine, and rapid rise.

How to activate fresh yeast

There is also yeast starter (which helps grow yeast or restart dormant yeast), sponge (a mixture of flour, water, and yeast often used for sourdough bread), and biga. Biga is used in Italian baking, mainly for types of bread with lots of holes, like ciabatta.

Fresh yeast is most often used by professional bakers whereas the dry yeast is for the home cook. But which version of dry yeast is best to have on hand? Since no one keeps six different varieties of yeast in their kitchen, this handy conversion chart will help you substitute the type of yeast you have in the pantry for what is called for in your recipe. Whether the recipe lists the yeast by volume, weight, or by the number of envelopes, this chart has you covered!

Yeast Variety Conversions

1 Packet (Envelope) of Active Dry Yeast Equals:
Unit Amount
Weight 1/4 oz.
Volume 2 1/4 tsp.
Instant Yeast 1 envelope or 1/4 oz. or 2 1/4 tsp.
Bread machine Yeast 1 envelope or 1/4 oz. or 2 1/4 tsp.
Rapid Rise Yeast 1 envelope or 1/4 oz. or 2 1/4 tsp.
Fresh Yeast 1 (0.6 oz.) cake or
1/3 of (2 oz.) cake
Yeast Starter, Sponge, Biga 1 cup

Tips for Using Yeast

Many people find using yeast intimidating—knowing if it is still active, getting the right water temperature, whether to add sugar or not. But yeast doesn’t have to be scary. By following a few tips, you can become comfortable incorporating yeast into your baking.