Imagine a product that is vitamin rich, yields a byproduct that makes us appear more youthful (we hope), and is good for the environment.
Well then, say hello to the humble blackcurrant.
Scientists from the University of Leeds, in Britain, say they have developed an effective new hair dyeing technology using the skins left over from the production of Ribena fruit cordial.
A new study published in the Journal of Agricultural and Food Chemistry says some of the ingredients found in synthetic hair dyes are derived from petrochemicals and are known irritants that can trigger allergic reactions.
Also, the report says, an estimated 95% of all hair dyes end up washed down the drain, with an unknown effect on the environment.
Colour chemist Richard Blackburn and organic chemist Chris Rayner, both from the University of Leeds, set out to identify and isolate naturally occurring hair-dye alternatives – and a sustainable process to produce them.
“Because of issues and concerns around conventional dyes, we wanted to develop biodegradable alternatives that minimise potential risks to health and offer consumers a different option,” Blackburn says.
He and Rayner led a team that combined expertise in extraction technology, hair science, coloration, and natural products chemistry to develop a new technology to extract anthocyanins from blackcurrant fruit waste for use in renewable dyes.
Anthocyanins are antioxidants that provide pigmentation to most berries, flowers, and many other fruits and vegetables. “They are non-toxic, water-soluble and responsible for pink, red, purple, violet, and blue colours, and are widely used as natural food colorants all over the world,” Blackburn says.
“We knew they bound strongly with proteins – hair is a protein – so we thought if we could find an appropriate source of these natural colours, we might be able to dye hair.”
The UK Blackcurrant Foundation says as much as 95% of the UK blackcurrant crop, about 12,000 tonnes a year, goes into making Ribena cordial.
The drink was originally made by British company HW Carter as a blackcurrant squash. It was launched in 1938, deriving its brand from the botanical name for the blackcurrant, Ribes nigrum. Because of its high vitamin C content, in 1939, during World War II, the drink was given to British children free as a supplement.
For readers in the US, a little background is in order: most Americans have never eaten a currant – “probably fewer than 0.1%”, Marvin Pritts, professor of horticulture at Cornell University in New York, told the website Business Insider in 2016.
In the late 1800s, the US had almost 3000 hectares of blackcurrants, gooseberries, and white currants, all in the genus Ribes, under cultivation. But when investigators found that blackcurrants helped spread a fungus introduced from Europe in the 19th century that killed white pine trees, the backbone of the nation’s timber industry, the federal Government outlawed commercial cultivation in 1911 and financed a program to eradicate the plants.
Gradually this prohibition has been eased on a state-by-state basis.
After being pressed to extract their juice, the skins of blackcurrants remain as a waste product.
“They have very high concentrations of anthocyanins and represent a sustainable supply of raw material because of how much blackcurrant cordial we drink,” Rayner says.
“The extraction technology is based on sustainable concepts – the colour is extracted using a water-based process and special filters collect the anthocyanins we want. We believe that if we are extracting natural and food-grade products, we should not use any toxic or hazardous chemicals to get them.”
In a second, forthcoming paper, the researchers analyse the extract in detail and identify all of its natural compounds.
“We wanted to identify all of the natural compounds present to improve our technology and to ensure safety, which cannot be said of most ‘natural’ cosmetic brands, where there is little understanding of what is in ‘natural extracts’,” Rayner explains. “Natural does not necessarily equal safe.”
The researchers have commercialised their discovery through a University of Leeds spin-off company, Keracol Limited.
Jeff Glorfeld is a former senior editor of The Age newspaper in Australia, and is now a freelance journalist based in California, US.
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