Some coloring matters in common use, such as the annatto, universally employed in coloring butter, are believed to be without harmful effect, but others are to be viewed with suspicion, and still others, like copper sulphate, are unquestionably dangerous.
"Food Poisoning"
Edwin Oakes Jordan
annatto is sometimes added to milk to increase its richness of color.
"The Mother and Her Child"
William S. Sadler Lena K. Sadler
To test for annatto proceed as follows: To a couple of tablespoons of milk add a pinch of ordinary baking soda.
"The Mother and Her Child"
William S. Sadler Lena K. Sadler