Marmite is perhaps one of the most divisive condiments on the market.
But love it or hate it, turns out few people really know what the dark, sticky goo is made from and why it tastes the way it does - and the shocking reality has left people totally grossed out.
In Channel 4's 'Food Unwrapped,' presenter Kate Quilton travels to a factory in Burton-on-Trent in Staffordshire to try and gain top secret knowledge of how Marmite and other yeast extracts are made.
"When breweries make beer, they take a sugary solution and they'll add yeast to it, and the yeast will convert the sugar into alcohol," explains Sinjin, who is the quality specialist at the factory.
Kate goes onto explain that the yeast cells multiply as they produce alcohol, and as a result, the breweries end up with a whopping seven times more yeast than it started with.
This is then sold to make yeast extract.
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After it arrives from the breweries, Kate notes that it's then pumped into large vats called coppers.
"What's happening there is we adjust the temperature so the yeast starts to decay," explains Sinjin.
Kate proceeds to explain how the coppers are heated to 95 degrees which kills the live yeast and breaks down their cell walls.
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"The yeasty soup is then put through a centrifuge to separate it into two liquids - the broken down cell walls and the cell innards," she says.
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Holding onto a bottle, Kate notes: "You've gutted every single sell of that yeast and that's what's in here - and that is yeast extract."
Sinjin then goes on to show Kate a further piece of vital equipment needed in the process.
"This will heat up the liquid and boil off steam," he says.
Discussing the next steps, Kate continues: "Once the water has evaporated, the yeast extract becomes concentrated and should start to look like something a bit more familiar."
But that's not all - she points out that six secret ingredients are then added.
"According to the label, it contains barley, salt, vegetable juicy concentrate juice and celery - but whatever it is, it's blended with the yeast extract and fills 25 million jars a year," she explains.
The revelation has since left Marmite lovers and haters horrified.
"So basically it's dehydrated yeast guts mixed with vegetable stock," wrote one.
A second penned: "Toast, Marmite and Beer. Yeasty way to start the day."
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A third wrote: "Oh gosh I can't eat this anymore...but my childhood though."
Meanwhile, a fourth added: "I think it's less of a question of 'how,' and more of a question of 'why.' I'm joking. I'd love to give it a go."