If you’ve never thought to yourself, “I really wish I could eat apple juice that had the consistency of caviar with my breakfast today,” don’t worry – I haven’t either. But sometimes the things we never think we’d want or need become wonderful parts of our lives. At least, that seems to be the idea of the molecular gastronomists who are making food in all new shapes and sizes.

An important new shape in culinary circles today is the sphere. Don’t we eat all sorts of things in the shape of a sphere already, you ask? Well, it’s true that we eat coconuts, chocolate truffles, oranges, mozzarella balls, and many other spherical foodstuffs. But all these foods have something in common: they’re solids. The new technique chefs are using, called spherification, makes liquids into spheres.

Raspberry caviar on blueberry gel // Shutterstock

Imagine instead of eating pasta drenched in tomato sauce, you spoon tomato-sauce-balls on top of your penne. Instead of sipping a glass of apple juice, you get a textured geometric burst of flavor when you eat a few apple juice spheres. Spherification can change the textures of our most beloved liquids, preserving their tastes but imbuing them with something new and different.

But unless you’re Albus Dumbledore, you can’t make liquid into spheres without some help. Liquid doesn’t just naturally hold itself in a certain shape: individual molecules aren’t bound together like they are in solids. Only weak bonds exist between liquid molecules, which means they slosh around at random. To make a liquid into a shape, chefs have turned to chemistry.

Specifically, they’ve turned to a molecule called sodium alginate. The chemical is made up of carbon, hydrogen, oxygen, and sodium. When combined with calcium, sodium alginate slightly solidifies into a thicker, gel-like substance.

Let’s say you want to make liquid wine into caviar-like spheres for a fancy dinner party you’re having tomorrow night. The first step is to mix sodium alginate with your Merlot. For this to work, you have to mix well: the water in the wine has to completely surround the sodium alginate molecules so that there are no lumps of chemicals left in the solution.

Your goal is to get the sodium alginate and wine, which is still a liquid, to gel together. So what do you need to add? Calcium, in some form or another. In a separate bowl, mix together calcium lactate and water. Calcium lactate dissociates in the water, so that you end up with free-floating water molecules, chlorine ions, and – crucially, for our purposes – calcium ions.

The next step is to let droplets of the wine mixture fall into the calcium lactate solution. The trick is to use something like a dropper, syringe, or pipette to take up the wine solution. Holding your tool of choice over the calcium lactate solution, allow small droplets of the wine solution to fall into the bowl below. What happens will amaze and astonish you: as soon as it comes in contact with the calcium solution, the wine, already shaped like a sphere as it fell in a drop from the pipette, will instantly congeal into a small sphere that will not come apart. It isn’t true that the whole droplet of wine instantly becomes gelatinous. Only the very outside of the droplet – the surface area that comes into direct contact with the calcium – hardens. The result is a liquid sphere, surrounded by a very thin film that holds it together.

What happens exactly in that instant to form the film around the liquid? When the sodium alginate in the wine droplet comes into contact with the calcium solution, a substitution occurs. The Na+ in the sodium alginate gets kicked out of the molecule by calcium – Ca2+ – that takes its place. But whereas Na+ was only able to form one bond, Ca2+ is able to form two. This means that instead of binding to only one molecule of the alginate, each calcium ion binds to two of them. Each alginate molecule, instead of being separate entities, becomes bound to its neighbor. In this way, calcium acts like glue to hold sodium alginate together. Having become cross-linked by calcium, the surface area of the wine droplet becomes a skin of connected molecules, capable of suspending liquid inside.

Now that you know how to create liquid spheres, there are a lot of new recipes for you to try. How about olive oil caviar with your Greek salad? Tomato water spheres injected with basil oil? Maybe carrot, orange, and mango spheres for a burst of flavor with dinner? Check out more of the possibilities here.


Davidson On-line provides scientific information only and should not serve as an alternatine to madical or nutritional advice.
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Julia Rothchild
Davidson Institute of Science Education

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