Ask a Scientist: What’s the white stuff on my carrots?

Kay Cooksey is professor and chair of food, nutrition, and packaging sciences at Clemson University.
Kay Cooksey is professor and chair of food, nutrition, and packaging sciences at Clemson University.

Kay Cooksey is professor and chair of food, nutrition and packaging sciences at Clemson University. Here she explains where baby carrots came from – and why they sometimes seem to be covered in a peculiar white film. Questions and answers have been edited.

Q. What are the origins of those bags of baby carrots in the produce section?

A. Bagged, ready-to-eat baby carrots didn’t become a product you could buy in the grocery store until the late 1980s and early 1990s. These carrots are almost all produced in California by two main growers, Bolthouse and Grimmway. They are not actually “baby” carrots, but are full-grown carrots cut down to size. As a result, they are referred to as a “baby cut” in the industry. Baby cut carrots are cut from the lower two-thirds of a long, fully mature carrot. The remaining portion is used for juice concentrate, sliced and diced to add to processed foods like chicken noodle soup, or incorporated into animal feed. Their sharp edges are ground down like you would turn a wooden chair leg, using equipment similar to a lathe.

Q. What is that white film on packaged baby carrots? Is it safe to eat?

A. The white appearance of carrots, often called “white blush,” is simply how they look when they get dehydrated. Carrots are a root vegetable, so they hold a lot of water that would normally nourish the plant as it grows. After the vegetable is picked, it naturally gives off the moisture to the atmosphere around it. Even though the packaging is very good for preventing water loss, it still can’t stop dehydration because the protective skin of the carrots has been shaved off to make the carrots into the “baby” size.

Baby carrots look less intensely orange and sometimes whitish because the surface of the carrots is rough from the shaving process, and with time, water evaporates from the surface, making the light scatter differently than it would from the surface of a smooth, fully hydrated carrot. If you put the carrots in icy water for about 15 minutes, it will reduce the white appearance, and if you store them in the refrigerator in cold water, the white will go away entirely. They are perfectly safe to eat regardless of whether the white appearance is there or not.

Q. What kind of substances are used in the processing and packaging of carrots to keep them fresh?

A. Carrots sold as baby carrots are not genetically modified and no additives are used to preserve them. Just like other bagged produce, baby carrots are cleaned according to Food and Drug Administration guidelines with a chlorine wash to kill bacteria that could cause food-borne illnesses. The guidelines call for chlorine washes that contain 50 to 200 parts per million total chlorine, though some producers like Bolthouse Farms claim to use much less. For reference, typical tap water contains 4 parts per million chlorine. As a final step, the carrots are rinsed with tap water.