Blackcurrants on wooden background

Chemists transform Ribena leftovers into sustainable hair dyes

Image credit: Dreamstime

Researchers based at the University of Leeds have used natural dyes extracted from waste from the Ribena manufacturing process to create sustainable, non-toxic hair dye.

The global hair dyeing industry – already worth more than $10bn per year – is on the rise, with demand for both salon and home colouration growing.

While there is a huge range of dyes available on the market, concerns linger about the impact of synthetic dyes on the environment and on health: common ingredients in synthetic dyes can cause allergic reactions and have been proposed as possible risk factors for cancer. Even henna, a dye considered safe and natural, contains lawsone, which is categorised as toxic by the EU Scientific Committee on Consumer Safety.

“There have been health concerns around [synthetic dyes] for many, many years, but they’re still being used,” said Dr Richard Blackburn, a colour chemist based at the University of Leeds. “There have been a number of severe allergic reactions where people have actually died.

“There’s a lot of care taken in, for example, the textile industry, after dyeing to make sure the dyes are treated before they can be released. And of course, every time you dye your hair, it just goes straight down the drain, there’s no understanding at all of what happens to those dyes once they enter the water. Our motivation, from a toxicological perspective and from an environmental perspective, was to try to find something better.”

Blackburn and his colleague at the University of Leeds, Professor Chris Rayner, began by searching fruit and vegetables for naturally-occurring alternatives to synthetic dye which could be processed safely and sustainably. They found that the anthocyanins contained in blackcurrants and other fruit were ideal candidates.

These pigments – which are responsible for pink, red, purple and blue colours in fruit, berries and flowers – are water soluble, non-toxic, and bond strongly with hair.

The chemists began to search for a plentiful source of the pigment, and an acquaintance suggested that Blackburn and Rayner try contacting GlaxoSmithKline, which at the time produced the blackcurrant drink Ribena. Ninety per cent of British blackcurrants are used to produce Ribena, and after being pressed, a huge mass of anthocyanin-heavy blackcurrant skins is left over as a waste product.

“There was a little bit of serendipity about it, as there always is with scientific discoveries,” Blackburn told E&T. “It turned out that the waste was the perfect raw material.”

The pigment was extracted using a sustainable, mostly water-based process, which did not require any “horrible solvents” or other toxic compounds. Blackburn and Rayner were then able to incorporate this pigment into purple shampoo (used widely by bottle blondes to prevent their hair yellowing after bleaching) and a range of hair dyes in natural and unnatural shades. These dyes remain fixed for 12 washes, making them comparable with conventional semi-permanent hair dyes.

“The anthocyanins are interesting because they change colour with pH, so we can modify the conditions to get a blue colour, a red or violet colour as well,” said Blackburn. “We were missing a yellow component [to achieve brown colours], so we also combined it with a natural yellow dye called berberine, which comes from barberries. It’s an intensely yellow pigment; nature makes amazing colours as well!”

After more than a decade of work on the products, the researchers are preparing to launch their natural dyes this summer through a spinout company (branded as ‘Dr Craft’), supported by the University of Leeds.

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