For decades, concerns have been raised about the safety of synthetic food dyes, and while the evidence against them is still unclear, natural colorings are generally preferred. Most of these pigments are sourced from plants, although a few come from crushed insects. But frustratingly, not all colors are easy to find in these places.
"Blue colors are really quite rare in nature – a lot of them are really reds and purples," says Pamela Denish, an author of the new study.
[...] As you might expect, most of the anthocyanins in red cabbage are red or purple, but there are tiny amounts of blue in there too. After about a decade of trying, a team of scientists from a range of institutions and food companies has now managed to extract useful amounts of blue by converting other anthocyanins.
Doing so required exactly the right enzyme, so the team screened a library of millions of them, and used computational simulations to explore about 100 quintillion potential protein sequences. Eventually, they were able to design the perfect enzyme for the job of converting the red and purple anthocyanins into blue ones.
The end result, the team says, is a natural cyan dye equivalent to the widely used synthetic FD&C Blue No. 1.
Pamela R. Denish, Julie-Anne Fenger, Randall Powers, et al. Discovery of a natural cyan blue: A unique food-sourced anthocyanin could replace synthetic brilliant blue [open], Science Advances (DOI: 10.1126/sciadv.abe7871)