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Explainer - All You Knead is Yeast!

Yeast!
Sourdough is having a moment… I say a moment, but it skyrocketed in March and the Sourdough train doesn’t seem to be slowing down. However, sourdough isn’t the be all and end all of baking. Sure it’s super digestible, but it takes time to cultivate. 

So what else is available? What is the difference between baker’s yeast and brewer’s yeast? Active dried and instant? Can you substitute store bought yeast with anything else? 

We’re here to answer your bubbling questions… 

First up…


What is yeast?! 
Did you know that yeasts predate humans? Yep, yeasts are old. Not old like VHS is old compared to Netflix (or even DVDs), but hundreds of millions of years old. 

There are over 1,500 species of these single-celled microorganisms. Yeasts work by feeding on sugars and converting this into carbon dioxide, and with more time, alcohol. Yeast comes from an ancient word meaning bubble, and this is exactly what yeasts give bread and beer - bubbles! 

You’ll quite often hear the terms baker’s yeast and brewer’s yeast. Ultimately both variations will leaven dough, but brewer’s yeast has the tendency to be a bit more bitter. 

Leaven… what’s that? 
Simply any substance that causes your dough to ferment and expand. Yeast, sourdough, baking powder… all leavens. 

You can also refer to the act of leavening as the process involved in rising. Leavening is super simple to explain - it’s the act of gas and air being released by the ‘leavening agent’ causing your dough to rise and take on an airy, puffy nature. 

Is my Yeast (still) alive? 
We’ve all found that packet of Olde Ancient Yeast from 1982 down the back of the cupboard, and wondered - still good? 

As a quick test, get a cup of lukewarm water, sprinkle in some yeast and some sugar, and stir it up. If it dissolves and you get bubbles - your yeast game is good to go! Still sat there? May it rest in yeast. 

So… Baker’s yeast, active dried… Why are there so many types?!

Active Dried Yeast
Active dried yeast is live yeast that is dehydrated then ground into small pieces - it tends to look like slightly elongated grains of sand. You’ll find this type in small pre-portioned packets, or slightly larger tins. 

Although dormant cells, you do need to store with caution. Keep them at room temperature, or below, if exposed to high temperatures, the yeast will expire. If you’ve bulk bought (let’s face it, we all jumped on larger tins if we could find them - like a precious Faberge egg on the shelf!), you can store in the freezer, provided it's stored in an airtight container. 

Although the name ‘active’ might lead you to believe that it’s ready to go, you do need to activate active dry yeast in lukewarm water to check it’s activity. This process is called ‘blooming’ and the yeast and water mixture should foam in a few minutes. If the water is lifeless, I’m afraid so is your yeast, and you’ll struggle to get a rise from it. 

Active dry yeast is great for longer proofing times due to its fermentation process, providing a slightly deeper flavour to the trained palate. 

Instant Dried Yeast
Instant yeast is more consistent than its Active friend, is more potent, and can be stored in the same way. The granules are smaller and you’ll find that it provides a rapid rise. Unlike active dry yeast, you don’t need to dissolve in water before adding to flour, but many people prefer to. Instant yeast is very convenient as it generally needs a shorter ferment, plus you use around 25% less than active dry yeast. 

Fresh Yeast
Fresh yeast is harder to come by in supermarkets, it must be refrigerated and is sold in small cubes consisting of water and yeast. It feels a little like blu-tac, but is crumbly. 

It’s super important to store fresh yeast carefully. If mold appears on the yeast, do not use - it is not safe to do so. Ensure your fresh yeast is stored in an airtight container in the fridge. Generally it lasts for around a week or two. It can also be frozen, but please wrap tightly in plastic wrap before doing so. 

Fresh yeast is much stronger in flavour and is preferred by bakers for sweeter recipes. We recommend using around 70% more fresh yeast versus instant yeast, or around 60% more than active dry yeast. 

Nutritional Yeast
Nutritional yeast comes up a lot in vegan cooking, but all it’s good for is flavour. This is because of  the way it’s processed. The high heat kills the live cultures, rendering the yeasts unable to feed on sugars and create the all important carbon dioxide… So don’t use this expecting a rise… 

Sourdough Starter
It would be remiss of me to introduce sourdough starters, then not include them in this yeast masterclass. Sourdough is a homemade yeast made from fermented flour and water. A mix of bacteria from a number of sources, and yeast from the flour marry to create a home-made solution to leavening bread and other baked goods. Items baked using sourdough as the natural levain produce easy-to-digest, flavoursome products. 

Sourdough tends to rise slower than commercial yeast products, so you may have to wait longer. 

Poolish 
Poolish might sound complex, but it’s actually incredibly simple. It was introduced by Polish bakers and is essentially a pre-ferment. It’s similar to a sourdough starter, but you don’t have to spend days nurturing, feeding, and praying it doesn’t die. All it takes is a small amount of yeast (dry or fresh), and equal parts flour and water, making it 100% hydration. Mix together and leave for around 24 hours, before adding to your dough the next day. 

Biga
Biga and Poolish are often talked about together, that’s because they are very similar. Again, small amount of yeast, flour and water, then left to pre-ferment before adding to pizza dough. However, Biga is slightly drier at around 50-60% hydration than Poolish making it easier to handle manually. 

Tiga
Tiga was invented by Pizza Bible author and pizza king, Tony Gemignani. It’s like a Biga, but with a higher hydration at around 70%, making it trickier to handle. 

So… you can’t find yeast, don’t have time to wait for a sourdough starter, poolish, BIGA or TIGA, BUT you desperately want to make great pizza at home. What can you use as a substitute? 

Neglected tins in the baking cupboard...

Good old baking soda, baking powder or cream of tartar can give you a rise in your baked goods, but you’ll need to use more, and heavy handed sprinklings of these substances can leave a real distinctive (and not in a good way) taste.

Different strokes for different folks. You’ll have dough fans who vehemently argue that BIGA is better, whilst fresh yeast is commonly used in Napoli. Ultimately, use whichever method feels most comfortable for you. Remember to use our Ooni App Dough Calculator for help with measurements, and check out our YouTube channel for handy hints.

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