When we talk about dough, everyone’s recipe differs in some way. That is the beauty of pizza. No one person is doing it the same as another, but one constant in every recipe that is a must have, cannot live without, is yeast. The quantity of yeast may vary slightly, but to make great leavened pizza or bread yeast is a requirement. In all honesty, yeast has always been that magical ingredient that I never quite understood until I started doing extensive research about it. With flour you can google a clear-cut image of all the different parts a kernel of grain is made up of, and it is easier to understand what flour is from that. Yeast, on the other hand, is a single-cell organism that naturally exists in nature and in all our surroundings, but it is microscopic and cannot be seen in its natural state by the naked eye. It is companies like Red Star, Fleischmann’s and Lesaffre that have figured out how to harvest yeast and make it as consistent as possible and shelf stable. So, what really is yeast and how much should you be using?
Baker’s yeast is part of the fungi kingdom and the Saccharomyces Cerevisiae family. The big, long, fancy Latin name means that it is a sugar eating fungus. This type of yeast is naturally present in the environment, meaning sourdough is possible anywhere, but no two sourdough preferments are going to contain the same strains or quantities of yeast. For pizza making we are primarily concerned with four forms of yeast: cake or fresh yeast, active dry, instant or sourdough. The first three types are commercially made and can be bought and stored in the refrigerator. The last is a natural way of harnessing yeast through a starter or preferment. Commercially made yeast is a great way to maintain consistency within an operation. Sourdough on the other hand, although trickier to maintain and control, once harnessed will offer more variance in terms of flavor.
The difference between active dry yeast and instant comes down to potency and speed. There are different schools of thought that say you need more active dry as compared to instant if substituting one for the other and there are those that say you can use equal amounts. During the production and drying stages of dry active yeast, dead yeast cells are used as a coating around the live cells which is one reason why it is recommended that you bloom dry active yeast before adding it to your batch of dough. This coating of yeast cells also slows down the activity, thus delaying the fermentation process (which is another reason why some people tend to use more active dry than instant).
Instant yeast has a thinner coating of dead yeast cells, which means it dissolves faster and starts working faster. But there is such a thing as too much yeast. During the rising process, yeast eats sugar and then produces C02, alcohol and other acids as a byproduct. If there is too much yeast in a dough, too much alcohol is created and can weaken the gluten structure and produce a dough that does not rise well. Both instant and dry active are shelf stable, and if stored in a dry, airtight container it can last upwards of a year in the freezer.
Fresh yeast is a slurry of yeast and water that is compressed into a block resembling the consistency of feta cheese and is normally tan in color. Since it is alive, fresh yeast is extremely perishable and must remain in a cold refrigerated state. If the color is whiter than tan or brown and it is brittle in consistency or moldy then it will be unsuitable for use. Since fresh yeast is mixed with water, more fresh yeast, up to three times as much, will be needed in a batch of dough if substituting for dry active or instant.
Sourdough, or levain, is a way of harnessing the natural yeasts in your environment. Creating a sourdough can take up to five to seven days and requires a strict feeding schedule. Once your sourdough has a routine, you will be better able to control the consistency of your final product. Using a sourdough can add an immense amount of flavor to any recipe but can be very temperamental if conditions change and you are unsure of how to adapt. There are lots of resources out there that can help with how to get a sourdough going as well as how to maintain it. There are also pizza makers like Audrey Kelly in Boulder, Colorado, and Will Grant in Seattle, Washington, that use a sourdough in their operations and are a wealth of knowledge on the subject.
Determining which type of yeast you want to use is the first step. How much to use is a complex question. When you want to bake your dough and what your temperatures and conditions are going to be determine how much yeast you should use. Yeast is most active in a warm environment and begins to die around 120 F.
To help better predict how much yeast you will need, there are charts available online that can help you. Another term for these charts is inoculation. Based off the temperature you are working in and within how many hours you want to bake your dough, these charts will help give you a percentage of yeast that will get you to that final product. These charts are useful, but keep in mind that as soon as conditions change the numbers change, as well. How much yeast is determined by so many factors that there is no hard and fast number you can use every day. Yeast is a living thing and is always reacting to its environment and food source, meaning you will need to monitor these conditions and alter your recipe to ensure consistency. The science behind yeast and fermentation is complex, but understanding the basic principles that yeast eats simple sugar and is more active in a warm environment are great first steps into the crazy world of baking.
Laura Meyer is Administrator & Instructor, The International School of Pizza.