(Unsplash)

Food scientists from Stellenbosch University (SU) have made hand santiser using bread. 

During a week-long process, the team produce 18 litres of alcohol-based hand sanitiser from stale breadcrumbs, in their in-house fermentation tank.

"It smells just a little bit like toast," says Stefan Hayward, a postdoctoral researcher in the department of food science at Stellenbosch.

He is part of a research group in the department which normally focuses on ways to reduce food waste, and put by-products to use.

See also: Instead of Savanna and Klipdrift, some local distilleries are now making hand sanitiser

"Waste implies a need to discard something which has become useless and needs to be disposed of. We see waste products and the tendency to produce too much food not as a problem, but as raw ingredients or by-products that can provide the impetus to invent new ways of reducing, reusing and recycling," Hayward says.

The team decided to make their own hand sanitiser a day after the presidency announced the national state of disaster, by producing bio-ethanol from bread.

See also: SA has banned the export of face masks, hand sanitiser – and an unproven Covid-19 drug

“Bread is composed of 40% starch which can be used as an excellent carbohydrate source during the production of bio-ethanol via fermentation,” says Hayward.

Unsold bread past its sell-by date is generally returned to distribution centres from where it is discarded as waste, or at best used as animal feed.

The team combined 60 kilograms of breadcrumbs with hot water and added alpha amylase enzymes, a digestive enzyme that acts on starch in food, breaking it down into smaller carbohydrate molecules.

See also: There’s a run on hand sanitiser in South Africa - but experts say it won’t entirely help against coronavirus

They then adjusted the pH level to optimal levels to convert starch to sugar. The mixture was then incubated at 65°C for 60 minutes to produce sugar,  and cooled to 30°C before a specialised yeast strain used by the distilling industry was added.

The end product, which looks like mashed potatoes, was left at room temperature for seven days until the fermentation process was complete and they could start distilling.

From the initial 60 kg of bread in their first batch, they were able to produce 10.5 litres of 75% ethanol. This was combined with ingredients such as glycerol, hydro peroxide (which also kills viruses and bacterial spores) and a denaturant to ultimately make 18.2 litres of hand sanitiser. 

"We were able to satisfy our scientific curiosity whether or not we would be able to ferment bio-ethanol from a waste product such as stale bread, and at the same time were also able to apply our knowledge to produce an antiseptic formula that can be of help in this time of crisis," says Hayward.

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