And now, at a time when the world is looking for a solution that can feed 10 billion human beings by 2050 while also reducing greenhouse-gas emissions generated by food production chains, many are turning to this ancient fungus to shape the texture as well as the taste and smell of future food.

In 2020, as more than three billion people found themselves under lockdown, many decided to learn how to make homemade bread. They needed a lot of flour – resulting in shortages rivalling only those of toilet paper and pasta in many places – as well as yeast, preferably fresh or active baker’s yeast.

This, too, became one of the most-sought products during this unusual period. Indeed, unless you were making homemade sourdough with a starter (which requires rigour and a lot of upkeep to maintain), yeast is essential to one’s homemade loaf.

Carefully protected from the air by paper packaging, the smell that emerges once it’s unwrapped is unmistakable, coming from the sugar beet or sugar cane molasses used in its production. One gramme of yeast contains 10 billion living cells – small, single-celled fungi that produce gas when they feed on the sugars in the flour.

Age-old ingredient

French scientist Louis Pasteur is credited with having first understood and deciphered the fermentation process, which generates carbon dioxide and ethanol, in 1857. This process is responsible for both the smell and taste of bread.

Although the mechanisms of and major possibilities offered by yeast have only been fully understood for a short time, humans have been using such substances for over 5,000 years. Its existence goes back as far as 16,000 years ago, and a study suggests that yeast originated in China.

The effects of saccharomyces cerevisiae, and of fermentation in general, have been linked with magic or divine powers. Since the beginning of human history, ferments have been used in food and drink in various communities, including the Babylonians who created early beer recipes.

In Georgia, ferments were used to make wine. Large egg-shaped jars were buried in the ground, in which grape juice had been collected, along with the skins, seeds and stalks, and left to ferment for months.

Not only does saccharomyces cerevisiae enable sugars to be transformed into alcohol, it participates in the production of aromatic compounds that give taste to the beverage.

In Egypt, where thick beer with a taste of ginger and honey was consumed, another recipe also using fermentation was invented: bread. The story goes that a mixture of water, milk, barley and millet was left out but got cooked anyhow, giving rise to the very first sourdough.

In ancient Greece, dough was fermented using a soda substance or grape juice. And then, 200 years BC, the Greeks taught the Romans the principles of using brewer’s yeast.

High-protein food

Yeast contains a host of vitamins and can help reconstitute gut flora when antibiotics have damaged the microbiota. But these aren’t the only reasons supporting yeast supplements: a basic ingredient in recipes dating back thousands of years, yeast is food in and of itself.

The protein content of yeast biomass can be as high as 45-50%, and can help provide energy to the body. A paper published in the journal “Cell Systems” in 2018 showed that, in a single cell of baker’s yeast, there could be about 42 million proteins.

When looking for alternatives to animal proteins, the first reflex is often to replace them with plant proteins. But, on top of the extensive list of additives often used in meat-substitute products based on these ingredients, the carbon footprint of soybean cultivation poses an environmental problem: the plant is part of the agreement made by the European Union early last month to ban food imports whose production contributes to deforestation.

Many are looking to yeast as a key food of the future. Recently, the start-up Yeasty raised funds for its project, which aims to use the waste contained in the bottom of brewery tanks, extract a yeast protein, and then create a flour out of it.

Containing between 50 and 60% protein, this ingredient could then be used in plant-based meat alternatives to meat, as well as in vegan cookies or cheeses.

Saccharomyces-cerevisiae yeast is already being touted as a food ideal for feeding space travellers, according to a study in the journal “Nature Communications”. Using 3D food-printing technology, yeast could become the link in a production chain capable of reproducing the colours, textures and smells of the foods eaten on Earth.

Fermenting the future

Beyond yeast, the process of fermentation is being called on for producing the foods of the future. In 2020, Biospringer, a subsidiary of French giant Lesaffre, unveiled its aim to make a splash in the vegan foods market with a yeast protein, a naturally occurring and gluten-free ingredient.

Meanwhile in Finland, the startup Solar Foods has gone one step further by taking inspiration from a technology deployed by Nasa in the 1960s. This consists of cultivating microbes with the help of CO2, hydrogen bubbles and nutrients. Stimulated, these bacteria release proteins that can be isolated and then dehydrated to obtain a high-protein powder.

It might sound like something out of a science-fiction story, but Singapore has already authorised this product for a market debut in 2024.