Yeast is responsible for bread, wine, and beer. Do you need to know more?
Yeast is a single-cell microgranism in the fungi family. Its scientific name is Saccharomyces Cerevisiae which means “sugar-eating fungus.” It is tiny (It takes twenty billion yeast cells to weigh one gram) but very strong. Yeast serves as a leavening agent which causes the bread to rise and expand by converting the ferment-able sugars present in the dough into carbon dioxide and ethanol.
More Quick Facts
- Yeast cells are alive. You need to treat them nice and carefully until it’s time to execute them in the oven. Keep them warm and moist and don’t feed them too much sugar or salt.
- What you are using to bake bread is baker’s yeast. It is not the same strain that is used to brew beer (predictably called brewer’s yeast).
- It’s better (for the end product) to let the yeast do it’s job slowly. It will produce better flavor and texture every time.
- You can substitute or swap instant yeast and active dry yeast 1:1.
- You NEED to add salt, just not too much, to control the growth rate of the yeast. No salt will let the yeast grow wildly and it will burn itself out prior to getting the dough in the oven.
Types of Yeast
Fresh or cake yeast
Yeast cells compressed into cakes or blocks. It is alive and itching to go. It needs to be kept wrapped and refrigerated and used within a couple of weeks. If you use fresh yeast, you gotta use it or lose it.
Active dry yeast
This is the type you might be most familiar with from the grocery store. It’s the kind sold in the three-pack pouches. It often needs to be proofed (or turned on/activated) over warm water (or warm water with sugar) before it can be used. If the water/yeast mixture doesn’t get foamy after a few minutes, you might be dealing with dead or old yeast.
Sometimes also called “rapid rise” as if we didn’t have enough variations. It is sold in pouches, but sometimes jars or small one pound bags, this type of yeast does not need to be proofed first. These tiny pebbles are ready to be mixed right into the dough.
Things That Affect Yeast Activity
Especially true to active dry yeast, but important to consider for all types of yeast. If the water is too hot, above 130 or 140 degrees, you can easily kill off the living yeast cells. Be aware that a lot of municipal tap water includes some level of chlorine which is great at killing fungus, including yeast. Best to use bottled or filtered water if you can.
Like water temperature, dough temperature will speed up or slow down yeast development. Optimal dough temperature after mixing for yeast development is 70 to 90 degrees. Anything lower than 60 degrees will be too cold and anything over that 130 degree mark will be very, very slow or will be too hot and kill the yeast. If you are aiming to bake bread the same day, you should aim for a target temperature slightly over 100 degrees to get enough fermentation and rise.
Salt is critical to keeping yeast growth under control. It will force a slower rise (remember, better flavor and texture) and make it so you don’t have to punch down the dough (i.e., remove excess gas that will collapse too soon) as much during fermentation.
While yeast love to feast on sugar, it can be too much of a good thing. Like Thanksgiving dinner.
If you are using a bread recipe that calls for additional spices in the dough be aware that many spices are antimicrobial and will slow down the yeast activity.
Did you know that 25% of the yeast’s genes can be found in human genome. No wonder the smell and taste of bread has been keeping the species alive for thousands of years.