Baking Basics: Dry Yeast vs Live Yeast

 Ah, yeast. I get lots of questions about yeast. In Germany, you can buy dry yeast, which is the most common, and live yeast, which must be kept in the refrigerator.

But what's the difference between them? And can you convert from one to the other?

Let's talk about it.

So, first off, what is yeast at all? As opposed to baking powder or baking soda, which both have chemical reactions that creates carbon dioxide that cause leavening, yeast is actually a living organism. Yeast is a fungus. 

When you buy live yeast, the yeast is cooled between 0° and 10°C, so refrigerator temperatures, and it becomes semi-dormant and stops growing. It will come out of its dormant state when warmed up and given something to feed on. It is fastest to get the yeast to grow by giving it sugar, but you can also use flour dissolved in water. 

What about dry yeast? The same concept, except instead of forcing dormancy by chilling the yeast, dry yeast has been forced into dormancy by dehydrating it. This means it can remain dormant for much longer and need not be chilled. It needs to be rehydrated and given something to feed on to reactivate it. Just as above, it is usually dissolved in warm water and given sugar or dissolved flour to feed on. 

However, since yeast is a living organism, it won't stay alive forever. It can be killed. If it is allowed to remain dormant for too long, it will die on its own. Live yeast will live for about 4 weeks in the fridge before it starts to die. Watch your best if used before date. Dry yeast lasts for years, evidently. I tried to find out exactly how long it keeps, but I was unable to. Check the date on your package and double check if your yeast is still alive or not by trying to rehydrate it with warm water and sugar. If it forms some small bubbles, it's okay. If it doesn't, it has probably died.

Now, it's also possible that you have managed to kill your yeast yourself. You can kill yeast by adding salt to it directly. Salt will kill yeast. So, salt added to recipes calling for yeast should be mixed with flour first. That should keep it separate from the yeast. Another way to kill yeast is by heating it too hot. Many people heat their water or milk up too hot before mixing it with the yeast. Others sometimes allow yeast bread to raise in the oven on low temperature. Well, that's probably still too warm for yeast. You can kill your yeast that way. So, don't add salt to yeast and don't heat it up very hot.

At the end of the day, you will need to heat your bread, though, to bake it up. That's true. And as the bread bakes, it will kill the yeast and it will stop raising. The outside edges of the bread will die first and become hard and then often will split the crust as the middle part of the dough continues to rise before the yeast on the inside reaches a high enough temperature to kill the yeast.

But this is why yeast bread must be allowed to rise for at least an hour before baking. Yeast will multiply as it is allowed to sit and your bread will be lighter and fluffier the more you allow it to raise before baking.

Now, what if your recipe calls for fresh yeast, but you only have dry yeast on hand? Can you convert from one to the other? Of course. 

1 tablespoon dry yeast (typically 8g) = 1 block of live yeast (typically 40g). That's pretty easy, actually. As for when they work, dry yeast can need a bit more time to activate compared to live yeast. Otherwise, go for it. If your recipe calls for 1 tsp dry yeast, you will need 1/3 block of live yeast. If your recipe calls for half a block of live yeast, you can substitute 1/2 tbsp dry yeast. Just allow it to active for a few minutes before trying to use it.

I hope that information was helpful for you. Keep asking questions. If I don't know the answer, I will try to find it.

Watch us talk about yeast on YouTube here: https://youtu.be/A8NJO67L4j8

Schaut zu wie wir über Hefe auf YouTube reden hier: https://youtu.be/uYBDDT-6aUE