How now brown cow — Chocolate milk isn’t really a liquid

Apparently 7% of Americans think chocolate milk comes from brown cows. That’s about 1 in 14 people. Can you think of the 1 in 14 people you know who’s uncertain about chocolate milk’s origin? If you can’t then it might be you…

Chocolate milk comes from cows of all colours.

Chocolate milk doesn’t come from brown cows. As Nate Silver and your father might comment, it comes from both brown and white cows. Chocolate milk is an interesting food because it’s not really a liquid, it’s actually a very, very weak gel. Chocolate milk usually contains three ingredients: milk (including federally mandated vitamins), chocolate, & carrageenan.

Carrageenan is derived from ‘Irish Moss’ a kind of seaweed. It’s used in a wide variety of different foods. (Image:
You can find Irish Moss beverages in cans from a number of different brands. These use carrageenan to make thickened milk beverages.

Carrageenan is a food ingredient derived from Irish seaweed. It’s been used for hundreds of years as a food additive because it has some peculiar characteristics, especially when added to milk. Carrageenan, like many food gums, can interact with other food ingredients like protein, fat, and minerals to create 3D structures in food. In chocolate milk, this very weak gel keeps the chocolate from settling in storage. Carrageenan is used at very low levels in food and is “Generally Regarded as Safe” by FDA. Still, some people have reported gastrointestinal irritation after consuming carrageenan and there’s been some concerns about possible carcinogenic effects from animal tests. Still there isn’t much carrageenan in a glass of chocolate milk and I can’t say if it’s enough to make a difference on your health.

Many foods are built from gels — that is, they’re made up of liquid and solid components and their behavior is a mix of the two. We call these materials “viscoelastic” because they contain a component that is ‘viscous’ (i.e. liquid) and one that’s elastic (i.e. solid). The liquid part dissipates the energy it receives; the solid part stores it.

In hard engineering speak, we can model a viscoelastic material as a spring-dashpot system. The spring (right) stores energy while the dashpot (left) turns it into heat, dissipating it. If the spring-dashpot analogy doesn’t work for you, think about it like a pond of water vs. a trampoline. If you drop a bowling ball in one, ripples form around it and crash until the pond is still again. If you drop a bowling ball on a trampoline it bounces back the way it came.

I spent a few years in grad school studying food gels. It’s a tedious kind of study called rheology and it’s the foundation for food texture studies. Understanding how food components build 3D structures tells us a lot about how foods are made and what they’ll taste like. There are lots of different components that can build structures in foods and they build different kinds of structures depending on how their processed and sourced. The usual suspects are: proteins, fats, sugars, starches, and gums. Each deserves its own discussion because they’re all pretty different. But they all work on the same principle. Each creates a kind of edible scaffolding that gives a food texture.

Bread starts off as a gel (dough) and cooks into a spongy, dry material. The ‘scaffolding’ is easy to see and it’s made of proteins (gluten) and starch.

It doesn’t take a lot of carrageenan to gel and hold the chocolate in chocolate milk. About 0.02% is enough to prevent settling. That’s roughly 200 mg of carrageenan per liter of milk. Increasing the concentration to a measly 0.2% (or 2 g/L) could lead to more noticeable gelling and textures like flan. Some gums are pretty powerful.

Gels are important in food because they’re everywhere. How I see food has changed dramatically since I started studying them. Chewing gum, meat, eggs, bread dough, cake batter, gummy candy, tofu, and mayonnaise are all food gels. Keep your eye out for food textures, once you start to notice food gels, a whole world opens up.

The characteristic thickness of hot and sour soup comes from gelatinized starches. Starch is a pretty essential ingredient in Chinese (and global) cuisine. (Image source:

Of all cuisines, Chinese is, in my opinion, the most creative and replete with food gels. From starch-thickened sauces to soup dumplings (which are made using another food gum that also comes from seaweed: agar agar), Chinese cuisine demonstrates a mastery of food gels, probably more than any other. But for today, we can raise a glass of chocolate milk to the Irish for giving us chocolate milk!

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