Nutritional Yeast: How It’s Made
Nutritional yeast—golden powdery flakes that add a whiff of nutty, cheesy umami when sprinkled onto a freshly-tossed salad or bowl of popcorn. It might not sound like much, but it’s grown from one of the most well-known microorganisms used to produce some of your favourite foods.
Yeast and its reputation amongst cooks has risen over the years thanks to its many applications in baking, brewing, and fermentation. Even before humans had the technology to observe cells, people relied on yeast to produce their food, and many generations of people have yeast to thank for the production of widely-consumed products like bread, beer, and wine.1 In fact, it is believed that the Egyptians used yeast to make bread out of naturally fermented dough several thousand years ago, making this handy microscopic fungus one of the earliest organisms ever domesticated by humans.
Fun fact: Yeast is extremely resilient. If it runs out of food it creates yeast spores which can lie dormant for millennia. Scientists have been able to reactivate yeast spores collected from pottery at archaeological sites - even using these ancient yeasts to make sourdough bread and to brew beer.2,3
Nutritional yeast is the same species as baker’s and brewer’s yeast — a commonly-used strain called Saccharomyces cerevisiae – but it is ‘deactivated’ during the production process, so it can’t be used for leavening bread or making wine.
Growing yeast all starts with a pure culture of S. cerevisiae yeast, which is first grown under the sterile conditions of a laboratory before it is cultivated on a larger scale.4 Yeast producers store these pure cultures safely at sub-zero temperatures to prevent them from mixing with any other microorganisms that might contaminate them—only extracting small amounts when they’re needed for production.
Fun fact: You can use this same tactic at home to extend the life of your dry or fresh yeast—just pop it in an airtight container then into the freezer and it’ll survive longer! Some people even freeze their sourdough cultures when they go on holiday to keep it alive whilst they’re away.
When they’re ready, starter cultures are put in vats or fermentation tanks to grow, where they are kept happy and healthy thanks to carefully maintained pH and temperature (and a strictly regulated ‘diet’) for several days. This diet mainly consists of sugar, which often comes from the molasses of sugar cane or sugar beets.5 As long as it is provided with plenty of sugar, the yeast culture will ferment and release carbon dioxide and ethanol, and it’s these by-products that cause bread to rise and create the alcohol in beer and wine.6
Making Nutritional Yeast
Yeast grows quickly; in factories, several tonnes of yeast can be grown in just a few days. But what is the actual process of making nutritional yeast? When it comes time to harvest, a centrifuge is used to separate out the fermented yeast from its by-products and collect a milky liquid called ‘yeast cream’. Next comes pasteurisation, where this yeast cream is heated to deactivate the yeast cells—meaning that it stops fermenting and growing. This is why nutritional yeast can’t be used to leaven bread or brew beer!8
Fun fact: Yeasts float freely in the air around us. This is why you can grow your own sourdough starter over time by just leaving a flour-and-water mixture out on the counter — yeasts from the environment will settle on your mixture and start growing and fermenting.7
Adding Nutrition to Nutritional Yeast
On its own, nutritional yeast is relatively high in protein, fibre, and B-vitamins.9 It’s particularly popular amongst people following plant-based diets, as it is an excellent non-animal source of vitamin B12. Though the yeast itself doesn’t naturally produce vitamin B12, this vitamin is added during the production process to boost nutritional value.10
After fortifying the yeast with additional minerals and vitamins like B12, the final step of making nutritional yeast is to dry it out. First it’s dried in spinning dryers, and then rolled out into the familiar flakes or powders that we scatter over all kinds of food. This final form is then packaged and delivered to your local grocery aisle.
So there you have it: from some of the smallest cells comes a huge transformation of flavour and texture. The next time you pour a glass of wine, take a bite of sourdough toast or sprinkle some ‘nut yeast’ on your dish, give a thought to the minuscule yeasts that made these foods happen.
What’s your favourite dish that’s made even tastier by a sprinkle of nutritional yeast? Let us know in the comments below!