Did you know | Aug 30. 2022 - 3:59PM

What is a pigment? Is it organic?

When “simple” gets complicated by science


Wendy Walsh

Freelance writer and science lover

If you aren’t a scientist or an artist, there’s a good chance you consider the words “pigment” and “color” to mean the same thing. After all, color is one of the first fascinations of childhood. We start to learn colors at about 18 months, which is even sooner than we learn shapes and textures. So whether you fingerpainted or colored your way to proficiency, you were an expert far before you started stumbling across confusion-generating statements like “Pigments are better than paint” or “Pigments are insoluble.”

But here you are, and Pandora’s box has been opened. Read on for the non-scientific explanation that will help you understand how scientists talk about natural food colors.

In a nutshell, the scientific definition of a pigment is that it is a colored molecule/compound which is not soluble in water or oil. A colored molecule/compound which is soluble is called a dye. The part of the molecule/compound which delivers the color is called a chromophore. Food colors are for the most part dyes. In the USA, the term “food dye” is often used. In Europe and many other parts of the world, the term “food color” or “food colorant” is most commonly used, with “colorant” being a more scientific term as in “something that imparts color.”

Did your brain start contemplating if a chromophore is a molecule or a compound before you could tell it not to bother? If so, here are the explanations from small to large as explained by Britannica:

  • Chromophore: a group of atoms and electrons forming part of an organic molecule that causes it to be colored.

  • Molecule: a group of two or more atoms that form the smallest identifiable unit that always retains its composition and chemical properties. Molecules are bound together by a strong force. Oxygen (O2) is an example.

  • Compounds: a group of two or more molecules that are always in a fixed ratio and are bound together by a chemical reaction. Table salt (NaCl) is an example. All compounds are molecules, but not all molecules are compounds.

Finally, we’ll take one last dive down the rabbit hole to delve briefly into the meaning of an organic molecule. (Did you notice that in the definition of a chromophore?) An organic molecule is quite simply defined as a molecule that contains carbon. All living things are made of complex molecules containing the element carbon. Almost all natural colors are made from organic molecules. Even white, which comes from calcium carbonate, and black, which comes from carbonized peat, bamboo or coconut shells.

Does that mean natural colors are organic and artificial colors/synthetic dyes are inorganic? Actually, no. Artificial colors/synthetic dyes are typically made from petroleum and as we all know, oil comes from organic material that was buried in the earth and transformed to oil by high heat and pressure. So even oil and gas – once living plants and animals -- contains the element carbon.

So unlike at the grocery store, where “organic food” has a positive connotation,” in the world of chemistry “organic” is a neutral descriptor. Inorganic natural food colors are uncommon but exist, like iron oxide which is a mineral. The best thing to do when you see the word “organic” in a chemical sense is to disregard it as either a positive or negative signifier.

“Pigment” and “organic” are two words that create confusion when scientific and non-scientific worlds collide. If you work for a food manufacturer or are simply an interested consumer, it’s helpful to have this basic understanding.

"It's confusing when words about food ingredients mean one thing to a consumer and another to a scientist. "