Word of the Week: Hydrocolloid

Meet the most important ingredient you use the least of.

Working at the intersection of food and science, we come across a LOT of scientific jargon and terminology, from chemical processes (see: nixtamalization), to physical phenomena (see: non-Newtonian fluids), to species names (see: Aspergillus oryzae). We’ll be sharing many of these fun words with you in this ongoing series, Cook’s Science Word of the Week. Get ready to impress at your next cocktail party.

Water tends to flow fast and free. Which is great for drinking, for fish, and all sorts of other applications. But sometimes we want a water-based liquid to not flow so fast and free. Instead, we want to turn it into a thick gravy, wobbly Jell-O, or chewy gummy bears. To do that, we need to slow the water down.

The tried and true way to slow water down and change its consistency is, simply, to add stuff. When small added particles are dispersed in a liquid, they form what’s known as a colloid. If the liquid contains enough of the right kind of particles, then when the water tries to flow, the particles get in each other’s way and hinder the movement.

Some particles are very, very good at doing that. We call those particles hydrocolloids

Hydrocolloid molecules are long, tangly chains, and when they disperse in water, they snarl up with each other into a mesh that prevents the water from moving easily. And, because they’re so well-shaped for the job, hindering the water’s movement requires surprisingly small amounts of hydrocolloid: often just a fraction of one percent of the total weight of the water. Since so little needs to be added, hydrocolloids can modify the texture of a liquid while leaving its flavor largely unchanged.

Cornstarch and flour are many cooks’ first thickeners. Their long starch molecules have given millions of gravies a spoon-coating unctuousness. But, even though cornstarch and flour are technically hydrocolloids, they are not the most efficient thickeners. (The term “hydrocolloid” is most commonly used in referring to just the more modern additions to the pantry.) And this means that you have to add a lot to get the desired thickness—a tablespoon or two of cornstarch per cup of water. As a result, they can have a noticeable effect on the final flavor of the gravy, both contributing their own taste and damping down some of the flavor in the liquid.

Some old school hydrocolloids, gelatin and pectin, are valued by modern cooks but also found in earlier generations’ pantries. Adding pectin is the standard way to thicken a fruit jelly or jam (it works best in the presence of sugar, so it’s ideal for that task), and powdered gelatin adds luxurious body to stocks as well as the classic wiggly gelatin-based desserts. (Gelatin is unusual because it is a protein, whereas the great majority of hydrocolloids are long chains of sugar molecules.)

But the real A-list of the modern hydrocolloid set—those that are effective in minute quantities—go by names that may not be such household words: xanthan gum, guar gum, locust bean gum, agar, carrageenan, gellan gum, and methylcellulose. Guar and locust bean gums are made from seeds; xanthan and gellan are created by specialized bacteria; agar and carrageenan come from seaweeds (and have been used for centuries). The varying molecular structures of these hydrocolloids produce different effects: agar makes a brittle gel; gellan can make a chewy gel; and guar gum won’t form a gel at all, just a thick, slick goo. And different hydrocolloids prefer different environments: some work hot, some work cold, some need high pH or added calcium to work.

Hydrocolloids have gotten press for the special effects they can create: from spheres of juice to foie gras tied in a knot. But minute amounts of these ingredients can help out with many everyday culinary tasks. They can make a whipped cream stay foamy much longer; make ice cream smoother and less likely to form large ice crystals; prevent water oozing out of a sauce or purée; lend structure to a gluten-free dough; even give a barely perceptible full-bodied feel to a homemade soda or cocktail.

The world is thick with possibility.

Is there a word you wonder about? Email us!

Graphics by Jay Layman.


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