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Are insects used to make food coloring?

Q: A few weeks ago at a party the subject came up about food coloring. I told the guests about the red bugs that are raised to make #40 red. Isn't it used in a lot of things, like bacon bits for one?
JS, Stoneham

A: The red coloring from insects that you're talking about is called cochineal and comes from an insect of the same name that is native to Central and South America. The females are wingless and spend most of their time sitting on certain species of cactus, sucking up cactus juice. The males are smaller and have wings.

Of main interest for red dyes are the females, which can be knocked off the cactus and dropped into boiling water or otherwise heated or crushed to kill them. From their bodies, a red substance called carminic (or kermesic) acid is extracted.

The little things are only about 5mm long, and it takes about a million of their corpses to get a kilogram of carminic acid.

There are two forms of cochineal dye. Crude cochineal extract is made from the dried and pulverized bodies of the insects.

Carmine is a more purified form. To make carmine, you have to boil the dead insects in ammonia or sodium carbonate, filter, and add alum. The alum reacts with the carminic acid solution to form a bright red compound. Lime can also be added to get a purpler shade.

Carmine is a great dye for almost anything, from clothing to beverages (it's the red of Campari) to food (yes, it's used a lot for meats, including bacon bits) to lipstick and just about anything else. It is amazingly stable over time and one of the few colorings considered safe for eye makeup.

Food containing it has to be labeled as such, and sometimes carmine is called E120. Coming from insects it is not considered kosher, halal, or vegetarian, and some people can have allergic reactions to it.

Red dye #40 is a different substance. It is derived chemically from coal tar and is not an animal or insect product.

Dr. Knowledge answers your questions about science each week. E-mail questions to drknowledge@globe.com or write Dr. Knowledge, c/o The Boston Globe, PO Box 55819, Boston, MA 02205-5819. Include your initials and hometown.

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