Blue pigments are surprisingly hard to get hold of, not least because the color is exceptionally rare in nature. But now, chemists have discovered a cyan blue color that could be used as an alternative to synthetic blue food colorings.
The discovery by the University of California, Davis and food manufacturers Mars Wrigley was published this week in the journal Science Advances.
The color is harnessed from red cabbage, a vegetable with a deep purple coloration that’s used in many food additives. In particular, it’s drawn from the vegetables’ anthocyanins, a water-soluble pigment found in a variety of flowers and fruits, such as blueberries and aubergine, providing their deep red, purple, or blue hues.
However, only a tiny amount of the natural blue anthocyanin is found in red cabbage. So, instead, the researchers developed a way to turn other red cabbage anthocyanins into the desired blue anthocyanin using specially designed enzymes. With the helping hand of a powerful computer, they sifted through trillions and trillions of potential protein sequences to design an enzyme that would achieve this conversion with high efficiency.
The industry go-to for blue food coloration is known as brilliant blue FCF (FD&C Blue No. 1) or E133. According to the study, the newly developed natural cyan blue colorant is “nearly identical” to brilliant blue FCF and also capable of producing richer green colors compared to many existing natural blue colorants.
Even beyond the world of food colorings, finding new blues has been a surprisingly pressing problem with scientists. Two blue pigments that were regularly used in traditional paints come with some big problems: Prussian blue released cyanide and Cobalt blue is toxic. Other blue pigments have environmental or durability issues. This is why chemists were so pleased when they accidentally discovered YInMn Blue back in 2009, the first new blue pigment in 200 years.
As mentioned, blue colors are very rare in nature. Many of the colors that appear blue are, in fact, reds and purples. True blue can only be found in a few plants, but it’s thought that the sole animal to produce a true blue pigment is the obrina olivewing butterfly (Nessaea obrinus). Scientists believe it’s so rare because of the physics of light. Pigments appear the color of the light they reflect and don’t absorb. Blue light has more energy than most other light in the visible spectrum. For a plant, which obtains its energy through light, it would be foolish to reflect the high-energy blue.
However, as this new food coloring shows, it is possible to obtain a natural true blue if you have a few tricks up your sleeve.