Sulfite ammonia caramel (E150d) is a widely used safe food colourant at certain levels.
But Coca-Cola don’t always keep to these safe levels.
In 2012, the US-based Center for Science in the Public Interest tested Coca-Cola in nine countries and found that the quantities of caramel colouring differed — they even differed between a coke in Washington DC from one in California where the regulations are much stricter. These findings were published as Carcinogenicity and regulation of caramel colorings in the International Journal of Occupational and Environmental Heath, Volume 18 Issue 3.
And yes, since you might be asking, the level of caramel colouring used in their UK sample was too high.
[Featured image is by Lorena.]