Annatto Annotto, or Arnatto, a red coloring matter extracted from the outer part of the seeds of a Brazilian evergreen, called the bixa Orellana. Dissolved in an alkali, as a crude pearl-ash, its color changes to orange. It is used to color milk, butter, and cheese. Dyers, painters, and soap-makers also make use of it.

Though employed only for disguising other substances, it is itself probably more adulterated than almost any other article of commerce. It has been purchased containing over 60 per cent. of chalk, and is often found contaminated with red lead, so that cheese colored with it has been made poisonous. Other substances usually mixed with it are turmeric, rye, barley, and wheat flour, sulphate of lime, salt, alkali, Venetian red, and copper.