By definition, organic pickles must not contain any artificial colors (nor chemical additives or pesticides, while we’re on the subject).

In contrast, mainstream pickle manufacturers often use a synthetic yellow food coloring known as tartrazine to achieve that familiar gherkin color. It’s listed as Yellow 5 on food labels, and it’s also responsible for processed macaroni and cheese’s frightening neon hue.

U.S. Department of Agriculture microbiologists have been researching why commercially packed pickles can turn red and spoil. They recently identified a key chemical culprit: an interaction between tartrazine and the normal lactic acid bacteria (Lactobacilli) that form during the pickling process.