Australasian Science Magazine

Credit: robynmac/Adobe

By Edward Kerr & Benjamin Schulz

Vegemite is made from the spent yeast left over from the fermentation of beer. Can it be recycled to produce Vegemite beer, and how does it taste?

Love it or loathe it, Vegemite is one of Australia’s most iconic products. It was first manufactured in 1922 by Cyril P. Callister in Melbourne from yeast left over after beer brewing, but can it be used to make beer?

The key ingredients in beer are malted barley, hops, water and yeast. The sugars and nutrients released from the barley are used as food by the yeast, which ferments the sugars into ethanol and carbon dioxide, providing the alcohol and bubbles for beer. The barley can contribute flavour characters through different varieties or roasting, while the hops add a pleasant bitterness and protect the beer from infection.

Because yeast grows during fermentation, a large amount of spent yeast is produced for every batch of beer made. Vegemite is a food spread made from this leftover yeast. After collecting the spent yeast sludge, the yeast cells are broken open by the addition of salt and heat. No yeast should be able to survive this process, making it very unlikely Vegemite could be used as a source of yeast in beer brewing.

Nonetheless, in recent years Vegemite has been reportedly used in prisons and dry communities as an ingredient in illicit homebrew. Is this possible?

We set out to investigate. We first found that there was no living yeast in Vegemite. Instead, we found that Vegemite provides many of the nutrients needed for yeast to grow. Nothing happened when we mixed sugar and yeast, or yeast and vegemite, or sugar and vegemite. However, all three together – sugar, vegemite and a source of live yeast – were all that was needed to make Vegemite beer.

To test if any live yeast remained in Vegemite we spread Vegemite on agar plates with a rich source of nutrients. This is how we routinely grow yeast for research. Nothing grew on these plates, indicating that there were no living yeast in Vegemite.

In beer production, the malted barley provides the yeast with not only sugar but also protein and other nutrients. Was Vegemite providing these other nutrients?

We tested if fermentation occurred in solutions of sugar with different amounts of Vegemite added. Nothing happened without the addition of live yeast. If we added live yeast to the solution of sugar alone, no fermentation could be measured. However, fermentation was vigorous if we added live yeast to the solutions with sugar and any amount of Vegemite.

We confirmed this using an analytical technique called gas chromatography that measured the exact concentration of alcohol in a solution. Ethanol was found at roughly 3% in every sample with yeast and Vegemite. This is roughly the same amount as any mid-strength beer in Australia.

If Vegemite does not contain any yeast, where is the yeast coming from in illicit homebrew? Yeast is found almost everywhere in the natural environment: on fruit, plants, animals and insects. These yeasts might not make the tastiest beer, but they are certainly easy to get.

This leads to the question of how Vegemite beer tastes. Being keen homebrewers ourselves, we leapt at the chance to try out an exciting new type of beer.

Our first batch was made with table sugar, a healthy spoonful of Vegemite and standard brewers’ yeast. While alcoholic, this was disappointingly thin and bland, with a disturbing, pungent, yeasty aftertaste.

Undeterred, and remembering that our experiments had shown that fermentation took place even with very little added Vegemite, we refined our recipe. We found that sugar for the desired alcohol content and only a very small amount of Vegemite provided a flexible base to which all manner of ingredients could be added. Hops or ginger added bitterness, brown sugar gave tasty caramels, rolled oats gave a full mouthfeel, and a little yoghurt made a palatable sour.

Vegemite beer is cheap, but maybe it will also open a whole new world of homebrewing possibilities for the adventurous.