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News Article

Promising new blue food colour from red cabbage.

Researchers develop enymatic method to convert red cabbage anthocyanins to a blue version.

A new cyan blue has been developed using anthocyanins from red cabbage. The researchers designed an enzyme to convert cabbage anthocyanins to a blue version that is equivalent in colour to the chemical blue used as an industry standard- FD&C Blue No. 1. The work is published in Science Advances.

Blue is a big challenge in the food industry. A good blue is critical to getting other colours such as green in food. There are two standard blues FD&C Blue No.1 and No.2. They are both artificial. The industry is seeking more natural colours in response to consumer demand so a natural alternative would be very popular.

The currently used natural blues main come from anthocyanins in red cabbage or purple sweet potato. However those suffer from being undefined composites of different molecules that have a violet component that muddies the colour when combined with other food colours, according to the study authors. There is one anthocyanin (P2) making up less than 5% of the mix that has a very blue spectrum with much less violet.

The study, carried out researchers from across the world, aimed to understand what structure P2 had that made it blue. They found a structure of 3 P2 molecules complexed with an aluminium ion had the required colour properties. To obtain higher yields of P2 from red cabbage the researchers studied public libraries of DNA sequences of enzymes to find ones that would carry out a selective diacylation of the related anthocyanin molecules P6, P7 and P8 and convert them to P2. They tested about 46 genes and identified 17 enzymes that could make this conversion. The best naturally occurring enzyme was 1AUR, an enzyme that is involved in hydrolysing long fatty acid chains.

The researchers reengineered the structure of 1AUR to improve its interactions with P8 using computational methods to suggest the best protein sequence to achieve what they wanted. The new enzyme can produce the P2 molecule in bulk.

The P2/Aluminium complex is stable, losing only 14% of its colour over 55 days in sugar syrup. It was successfully used to create green food products similar in quality to the artificial dye.

The work was funded in part by Mars.


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Search for: blue (" food colour*" or "food color*")



Discovery of a natural cyan blue: A unique food-sourced anthocyanin could replace synthetic brilliant blue. Pamela R. Denish, Julie-Anne Fenger, Randall Powers, Gregory T. Sigurdson, Luca Grisanti, Kathryn G. Guggenheim, Sara Laporte, Julia Li, Tadao Kondo, Alessandra Magistrato, Mícheál P. Moloney, Mary Riley, Mariami Rusishvili, Neda Ahmadiani, Stefano Baroni, Olivier Dangles, Monica Giusti, Thomas M. Collins, John Didzbalis, Kumi Yoshida, Justin B. Siegel, Rebecca J. Robbins. Science Advances 07 Apr 2021 : eabe7871.


Article details

  • Author(s)
  • I. Hoskins
  • Date
  • 08 April 2021
  • Subject(s)
  • Food science