Seaweed didn’t exactly come into play during those “make your own ice cream” science experiments you probably did in elementary school, but it is sometimes used in the making of commercial ice cream. No, it isn’t just in seaweed-flavoured ice cream, either. Seaweed is actually used as a type of thickening agent for ice cream.

Technically, the substance usually used to thicken the ice cream is called “agar” or “agar-agar.” The name comes from the Japanese word for “red algae.” It was discovered in 1658 by Minora Tarazaemon, a Japanese innkeeper who supposedly left extra seaweed soup outside overnight. It was winter, and the substance froze. Tarazaemon noticed in the morning that it had turned into a sort of gel when it thawed again.

Whether that’s exactly how Tarazaemon discovered it or not, it was later found that after first boiling seaweed, repeated thawing and freezing makes a pure, gelatinous substance perfect to use as a thickening agent. It’s likely that the process was picked up by the Dutch in the 17^th century and later spread to other East Indies ports.

Today, agar is used in a variety of processed foods as an emulsifier or binding agent. Not every country or company uses it; some use carrageenans instead, which is made from certain red seaweeds. The use of different substances is based purely on preference and availability of resources. For instance, during World War II the availability of agar was low, so many companies switched to using carrageenans instead and stuck with it even after agar became more widely available again. (A similar thing happened with Twinkies, where during WWII bananas were in short supply, so Hostess switched to using a vanilla cream filling, rather than banana cream.  The vanilla cream filling turned out to be much more popular, so they never switched back to banana cream filling, though kept the banana-like look to the Twinkie anyways.)

But you make homemade ice cream with just milk, sugar, and a bag full of ice and salt—so why is a binding agent needed in the production of commercial ice cream?

The basic components of ice cream are fat (usually from milk), sweeteners, air, ice crystals, and “other solids” which includes non-fat milk solids and various flavours (like bits of cookie). When the ice cream liquid is prepared, often an emulsifier and stabilizer must be added to keep all the ingredients together and improve the texture. That’s where the seaweed comes into play.

Most commercial stabilizers these days are vegetable gums—that means agar, carrageenan, or something like Xanthan gum (derived from bacteria found in cabbage). These stabilizers keep ice crystal growth small by immobilizing the liquid in the ice cream—sort of by acting like a sponge. Larger ice crystals, caused by too much liquid in the ice cream, will make the ice cream feel grainy if a stabilizer is not used. The stabilizers also help keep the ice cream from melting too quickly so that you can enjoy your ice cream for a longer amount of time on a hot day.

That said, more stabilizers do not equal higher quality ice cream. Quality ice cream typically contains more fat and less air, while lower quality ice cream substitutes a higher quantity of stabilizers for fat, and often contains more air molecules.

If you liked this article, you might also enjoy our new popular podcast, The BrainFood Show (iTunes, Spotify, Google Play Music, Feed), as well as:

• What Causes Ice Cream Headaches
• Ben & Jerry’s was Originally Going to Be a Bagel Company
• Häagen-Dazs and Frusen Glädjé are Both American Companies
• The History of Ice Cream
• Hawaiian Punch was Originally Supposed to Be an Ice Cream Topping

Bonus Facts:

• Agar and other plant-based thickeners are a perfect substitute for the better-known gelatin. This is particularly true if you’re a vegetarian looking for a non-animal-based thickening agent. For those of you who might not know, gelatin is made by extracting the collagen from an animal’s bones. If given the choice between seaweed ice cream and animal bone Jell-O, which one sounds more appetizing? 🙂
• Ice cream isn’t the only place you’ll find seaweed in your kitchen. Other items containing agar or carrageenan include salad dressing and jelly. It can even be found in some beers. You might also find it in your toothpaste—never thought you’d be brushing your teeth with seaweed, did you?
• You might find carrageenan, kelp, or simply algae extract listed on some of your favourite beauty products. It’s present as a thickening agent in lotions and creams, but studies have shown that the plant is also beneficial to your skin. Containing sixty different minerals, it is a natural detoxifier which draws out toxins from your skin, making it look younger. Its ability to temporarily tighten skin makes it a popular component of anti-wrinkle and eye creams. Stick to the beauty creams, though—rubbing ice cream on your face will probably just make it a little sticky and attract flies and ants. 😉
• If you’ve ever had braces, you might have tasted a type of seaweed powder. That yucky, almost doughy-tasting gook they put in metal trays to make impressions of your teeth is usually made with alginate powder, derived from seaweed.
• In Japan, agar-agar is a popular bulking agent called Kanten. There is even a “Kanten diet.” Agar is roughly 80% fiber and has barely any calories, so it’s considered somewhat “healthy” by some. If you’re trying to lose weight, though, I don’t think eating ice cream with agar in it is going to help you.
• Agar isn’t just used in food production; it also has uses in microbiology. Agar provides a solid surface to aid in the growth of fungi and bacteria. The gel won’t be destroyed because many microorganisms can’t digest agar. The method was first used by a laboratory assistant of Robert Koch, who saw his wife using agar to make confectionery jelly in the kitchen. Koch believed that agar had potential in the laboratory and ended up using agar to make the first culture of tuberculosis bacillus. Agar also allows for seedling germination in petri dishes, provided the seeds have been sterilized.
• You might also find seaweed in children’s modelling clay.
• Some studies have shown that carrageenan might be able to protect you from some STDs, but we don’t recommend you pig out on ice cream and put the theory to the test.