On Leavening: How Many Types of Yeast Exist?

In many recipes for cakes and all bread preparations, yeast is a common ingredient. But what exactly is yeast, and what does it do? There are primarily three types of yeast: brewer's yeast, natural yeast, and chemical yeast (or instant baking powder for sweets).

All these yeasts serve the purpose of leavening dough, though in different ways. They produce gas within the dough, causing it to rise, expand, and increase in volume. This process ensures that, during or after baking, our bread or cake becomes fragrant, well-aerated, and soft to bite into and enjoy. Let’s explore how each type produces gas differently!

Brewer's Yeast

Brewer's yeast, named after its historical discovery in beer fermentation sediments centuries ago, is a single-celled organism classified as Saccharomyces cerevisiae in the fungi kingdom. It has played a significant role in human nutrition for its use in making bread and various leavened pastries. Additionally, it has been known since ancient times for producing beer (hence the name) and wine. In baking, it is prized for its ability to produce gas, which causes dough to rise.

Like any living organism, yeast has a life cycle: it is born, consumes nutrients, grows, reproduces, and eventually dies. Once incorporated into dough and exposed to water at optimal temperatures (above 20°C), yeast begins feeding on the sugars (particularly dextrose) found in flour or the dough in general. The primary food source is the starch (a polysaccharide carbohydrate) that makes up most of the flour. Through natural enzymes in the grain, starch is broken down into sugars to feed the yeast. The yeast reproduces (via budding) and produces carbon dioxide (CO₂) gas and ethanol as by-products of its metabolism.

At a certain point, the gas produced becomes sufficient to "lift" the dough by stretching the gluten network (see the article on the gluten network) as it tries to escape into the environment. This process continues as long as the yeast finds sufficient food (sugars) in the dough. Before the dough begins to collapse or deflate, it must be baked to capture the leavened structure in the final product.

Commercially available brewer's yeast is sold in compressed blocks, typically 25 grams (500 grams for professional use), mixed with nutrients to ensure its survival until use. It should be stored between 2°C and 6°C to keep its metabolism low, allowing it to last about a month in the refrigerator.

A variation of brewer's yeast is dry yeast, which is simply dehydrated brewer's yeast. Through a process of freeze-drying (removing water from the yeast cells at low pressure and ambient temperature), the yeast is rendered inactive until it is rehydrated with water during dough preparation. This allows it to resume metabolism and gas production. Because it lacks water content, dry yeast has a longer shelf life and can be stored at room temperature.

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Dried Brewer's Yeast


Parlando di lievito, taluni parlano di lievito integratore come di un particolare tipo di lievito che migliora l'impasto. Probabilmente si fa riferimento non tanto a microrganismi cellulari ma a prodotti in polvere che servono a migliorare la lievitazione, soprattutto in presenza di farine qualitativamente modeste se non addirittura scadenti. In questo caso il “lievito integratore” o per meglio dire l'”integratore per pane” non ha la funzione di produrre gas ma di fare in modo che il gas prodotto sia trattenuto maggiormente all'interno dell'impasto (vedi l'articolo su “La maglia glutinica”).


Natural Yeast

Like brewer's yeast, natural yeast is a biological yeast. It consists of a mixture of flour and water that is acidified by a complex of yeasts (including Saccharomyces cerevisiae, the same species as in brewer's yeast) and lactic acid bacteria (Lactobacillus genus). These organisms initiate leavening by producing gas.

Unlike brewer's yeast, natural yeast ferments more slowly due to the presence of lactic acid bacteria, which produce organic acids. This results in greater dough rise, improved digestibility, and better preservation of baked goods (see the article on sourdough).

Natural yeast is also known as sourdough, starter, mother dough, or levain. It is essential for making traditional baked goods such as panettone, Easter dove cakes, and pandoro, as it can leaven heavy doughs more effectively. As a "slow" yeast, it requires 24 hours or more to fully leaven such products.

Making natural yeast is conceptually simple but practically challenging. It begins with a mixture of flour and water that undergoes spontaneous fermentation by microorganisms naturally present in the flour, water, and surrounding environment. The acidity can be accelerated by adding fruit, as the surface of many fruits contains natural yeast (Saccharomyces cerevisiae). This explains why natural yeast contains a large amount of the same yeast strain found in brewer's yeast.

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Mother Yeast with added Dry Yeast

Chemical Yeast

Chemical yeast (also called instant yeast or professionally, baking powder) is a fine white powder that reacts with acidic substances in dough in the presence of heat, releasing gas. This gas, much like that produced by brewer's yeast, causes the dough or batter to rise. The process is quick compared to biological yeast, making it unsuitable for bread or rich pastries like brioche or panettone but perfect for lighter batters like sponge cakes or shortcrust pastries.

In chemical yeast, substances like sodium bicarbonate (baking soda, additive E500) react with acids such as disodium phosphate (E450, commonly known as sodium pyrophosphate). This reaction releases carbon dioxide and water, leavening the mixture.

Popular chemical yeast brands include Lievito Bertolini and Lievito Pane degli Angeli (both by Cameo S.p.A.), which are often enriched with vanilla or other flavorings.

A variation of chemical yeast is cream of tartar, in which disodium phosphate is replaced with potassium bitartrate (E470a). This reaction is even faster, making cream of tartar ideal for specific types of cookies.

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Baking Powder for Cakes