Heriot-Watt University experts collaborate on developing alcohol from bread waste
Distilling experts at Heriot-Watt University are working with an Edinburgh distillery to develop a new alcoholic spirit made from bread waste.
Professor Annie Hill from Heriot-Watt’s International Centre for Brewing and Distilling and Chris Miles, owner of Folly Spirit Labs and The Black Cat pub on Rose Street, have already taste-tested samples and are now refining the process for potential commercial production.
For four years, Chris has been turning surplus apples from Edinburgh’s gardens, orchards and farms into Pochle Geal, a fruit spirit sold at his own bar and venues across Scotland. A conversation with a food-bank manager inspired him to look at bread.
Chris said: “A food-bank manager told me that one of their biggest challenges is bread waste. They receive lots of loaves from supermarkets, but it goes out of date before it can be distributed.
“Bread doesn’t have as strong a flavour as apples, and I started thinking about koji, which is used to make sake and other Asian spirits and by chefs to create flavour.
“The idea stuck, and I asked Annie to help develop it.”
Annie supervised two Heriot-Watt students investigating whether the idea could work, along with colleague Dr Kelly Stewart.
Using three strains of koji, white, black and yellow, the students grew the mould directly on slices of waste bread. Its natural enzymes broke down the starch into fermentable sugar, which yeast then converted into alcohol.
Annie said: “What makes this particularly interesting is that we’re not taking an expensive raw material and turning it into alcohol.
“We’re asking whether something that might otherwise be thrown away can become the starting point for a high-value product. Around one million loaves of bread are thrown away in the UK each day.
“There is lots more work to do. Different breads contain different ingredients and preservatives, and we need to understand which breads and koji cultures give us the most reliable results.
“But we’ve already shown that it can work, and that’s a really exciting starting point."
The team has selected one sample to take forward from the initial trials. Chris said: “I can see it being used as a cocktail base or spirit mixer. Bars across the city are looking for more sustainable products, so there should be a market for it. We’ll also try ageing some in casks to see what happens.
“Ultimately, I hope surplus bread and leftover pastries from local cafes and businesses could be collected or dropped off and we can save them from landfill and turn them into a flagship spirit for Edinburgh.”
A Heriot-Watt MSc student is now reviewing other starter cultures and production methods used in Asian spirits, while discussions are under way about further research to optimise the process for commercial production.
Pictured: Professor Annie Hill
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