Below is the outline of the process to make vegemite as printed in the Age:
THE Vegemite plant smells of yeast, like a winery during vintage, only sweeter. It's basically a series of big rooms stacked with stainless steel tanks connected to other stainless steel tanks by stainless steel pipes. The world's annual production of 23 million jars of vegemite is made here; 95 per cent of those are consumed in Australia and New Zealand. The rest are sold mainly to expat Aussies and Kiwis. A few make it to Tokyo, where umami-mad locals wolf down tiny frozen cubes of Vegemite in modern sushi bars.
When I mention to our hosts from the marketing department the popular conception that Vegemite is made from "beer sludge", they shrug their shoulders. We are soon down at the receiving tanks into which tanker trucks pump their loads of spent yeast, collected from the nations' breweries. All the action takes place within the stainless steel pipes and vats. The first stage filters off any remaining malt and hops and removes residual alcohol. The remaining yeast is then treated with heat and enzymes to remove the outside of the cell wall and to leave the rest of the yeast cell: protein, amino acids and B vitamins. This is cooked with salt at low pressure for four hours and is now referred to as yeast extract. It has been reduced by 40 per cent to a viscous liquid that looks like hot caramel sauce.
Our host takes a sample of the liquid. Like Augustus Gloop from Willy Wonka and the Chocolate Factory I can't help but taste this proto-spread. Compared with the finished product it is bitter, yeasty and aromatic with the flavours of the hops and barley still upfront; it's a long way from being Vegemite.
To finish the process, the contents of more than 30 of these drums are sucked up into a large stainless steel vat and further reduced.
Liquefied cooked onion and liquid celery seed, a small amount of caramel for further colour and flavour, and both sea salt and mineral salt are added. This goes into another cooker at more than 100 degrees for several hours, where further caramelisation takes place. What has become "black velvet" spread is extruded warm into jars and sealed.
FOUNDED: Vegemite was invented by chemists working at Fred Walker's eponymous cheese company, and was first sold commercially in 1923. The same company invented a beef extract called Bonox in 1918. In 1926, a company was formed with Chicago-based Kraft to make processed cheese in Australia. After Fred Walker's death in 1935, the Australian holdings of the company were absorbed by Kraft in Chicago.
DID YOU KNOW? Australians spread 1.2 billion serves of vegemite on toast and bread every year.
I doubt there would be any yeasties left alive.