How to determine which type of yeast to use and the amount?
First and foremost it is important to understand that the answer is highly dependent on the conditions: there is no right or wrong yeast or right or wrong amount. It all depends: we have to establish the method we are going to use and consequently reverse engineer the yeast requirements. This article is not meant as a replacement for doing our own research or our own experiments. It is a starting point for getting the results we want.
Is commercial yeast bad for our health? Should we use it in small amounts?
Let’s clear some misconceptions first: yeast is not bad for health. In fact, it is impossible to cook a pizza without killing the yeast in the oven and consequently, our health cannot be affected. Nothing would survive above 60° C (140° F). The argument in favor of using a small amount of yeast and its connection to a better quality or healthier pizza is wrong. Not only does yeast die in the oven, but it also multiplies exponentially when we do the leavening. So if, for example, we use less yeast we will inevitably do the leavening at a higher temperature and/or for a longer time, and we will let the yeast multiply as we ferment. So what is the point? Just because we added less yeast, it doesn’t mean there is less yeast once the dough is ready to be used.
Does the amount of yeast even matter? Or can we add as much we like?
It absolutely matters, certain processes are executed successfully when done with specific amounts of yeast. Changing the yeast amount can lead to a different outcome or a disappointing pizza. After all, there are good reasons why Piergiorgio Giorilli coded the biga specifying the usage of 1% of fresh yeast and fermentation of 18h at 18° C (64° F). There are lots of reactions happening inside the dough, and rigorous experimentation done by experts cannot be replaced with a couple of tests at home and a self-made recipe. Even if we do a simple direct dough the yeast amount matters because we want the dough balls of the correct size when we need to use them.
How different is fresh yeast compared to dry yeast? Is it correct to use 1/3 of the yeast amount when we replace the fresh yeast with dry yeast?
Fresh and dry yeast is made by the same kind of living organism: Saccharomyces. The results are not identical, but comparable. In theory, it sounds correct to use 1/3 amount since 2/3 of fresh yeast content is water, which obviously dries up in the case of dry yeast. In reality, this is not correct: in fact, yeast loses some power while drying and it activates a bit slower once in use. Basically, when we use dry yeast we have to use 50-60% of the amount of the fresh one (please notice that the conversion might not be identical for different processes).
So what is the correct yeast amount?
The pragmatic answer is: the amount that is required, for the specific process to get the correct size of dough balls (and bulk size if we do bulk fermentation). Consequently, we can say that the amount is wrong in case that, by the end of the process, the dough balls are not well grown or collapsed (and bulk size, if we do bulk fermentation). The amount ranges quite a bit: from way under 0.1% to over 1% of the total flour.
So how to decide the yeast amount? Let’s see some practical examples, Please note, the amounts below are not accurate since it depends on the exact temperature and leavening time.
Direct dough
For direct dough it depends on how we want to ferment: if we go for a room temperature leavening, we can use a small amount of yeast (for example 0.1%). We’ll be ready to make our pizza in 8-24h.
If we do cold fermentation we can use a higher amount (for example 0.3%) and the fermentation would be longer: 24-48h or so.
Biga
With biga we don’t really decide the yeast amount, but we decide the biga percentage in the dough. Now assuming that we go for Giorilli biga with 1% yeast, we can go for a percentage of biga between 30 to 100%. If we decide to go for 30% we have a dough that we can cold ferment for around 24h. On the other end if we go for 100% we probably have just 6-10h of fermentation time. In this case, considering the high yeast amount, we might have to skip the bulk fermentation or reduce it to 30-60 min to avoid overgrowth.
Sponge
Dealing with the sponge is similar to dealing with biga, except for the fact that the yeast amount in the sponge varies a bit: 0.8-1%, and consequently it might take a couple of extra hours to grow.
Poolish
Poolish can be done with different yeast amounts in consideration of the duration of the poolish.
Doing a 2h poolish requires a lot more yeast compared with an 18h poolish. Generally speaking, a longer poolish will give better results, so if we have the time we should do a 12-18h poolish that contains a moderate amount of yeast. Before making the dough we should choose a poolish amount and then we might decide to add yeast while kneading. If, for example, we use 0.2% yeast and we use 50% poolish, our total yeast amount will be 0.1% which is small. So we can easily add more to the dough, maybe 0.2-0.5%: the leavening time ranges again between 6-24h.
What about pizza apps?
When we input data in a pizza calculator we put certain amounts and leavening temperatures. The calculator does not include the dough closure temperature and doesn’t consider the type of containers used. Both factors impact the results significantly. In other words, pizza apps cannot be accurate because the input options are insufficient to determine the results.