NATURAL DYES EXTRACTED from blackcurrant waste created during the manufacture of Ribena have been used in an effective new hair-dyeing technology.

The technique could produce dyes that are less toxic than some of the products currently used.

The researchers, based at the University of Leeds, tried grapes as well as blackcurrants but the smaller berries yielded much more of the vital colourant.

The researchers developed a patented hair-dyeing technology that provides intense reds, purples and blues on hair that, when combined with a natural yellow, could provide a wide range of colours – including browns.

The colours produced lasted for at least 12 washes – comparable to conventional semi-permanent dyes.

The global hair-colouring industry is worth more than €8.6 billion a year, with the number of people colouring their hair in professional salons and at home rising.

Allergic reactions 

Some of the ingredients found in commonly used synthetic hair dyes, which are derived from petrochemicals, are known irritants and can trigger severe allergic reactions.

There is also much debate about whether these ingredients could increase people’s risk of developing cancer.

Those used in permanent dyes and to achieve darker shades are of particular concern, although many colourants used in semi-permanent ones also carry risks.

The main natural colourant used in henna, considered to be more ‘natural’, is lawsone, which the EU Scientific Committee on Consumer Safety has described as toxic.

On another note, up to 95% of all dyes end up washed down the drain; their effect on the environment is unknown.

Sustainability 

Colour chemist Dr Richard Blackburn and organic chemist Professor Chris Rayner worked together to identify and isolate naturally-occurring alternatives – as well as a sustainable process to produce them.

Blackburn, who heads the Sustainable Materials Research Group at the University of Leeds’ School of Design, said: “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.”

Professor Rayner, from Leeds’ School of Chemistry, added: “We’ve made it possible to have great hair colour, and to get it from nature in the most sustainable way possible.”

A paper on the research was published in the Journal of Agricultural and Food Chemistry during the week.

“Anthocyanins are pigments that provide colour to most berries, flowers, and many other fruits and vegetables,” Blackburn explained.

They are non-toxic, water-soluble and responsible for pink, red, purple, violet and blue … and are widely used as natural food colorants all over the world.

“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.”

Ribena 

All but 10% of British blackcurrants are used in the production of Ribena; the berries are harvested in late summer and pressed for juice.

Professor Rayner said: “After being pressed, the skins 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.

The extraction technology is based on sustainable concepts – the colour is extracted using a water-based process and special filters collect the anthocyanins that 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 separate upcoming paper, the researchers analyse the extract in detail and identify all of its natural compounds.

Rayner said: “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.

‘Natural’ does not necessarily equal safe.

The blackcurrant-based dyes should be on sale this summer, and the researchers have also made the “first natural purple shampoo”.