You thought lab-grown meat was the best horror that science could toss at you? You're wrong. Molecular gastronomy has found a way to pitch gelid balls of liquid-filled goo food at you. Find out how to put a 'skin' on apple juice, and what that has to do with a bizarre process called 'food spherification.'
Photo via I Wish I Had a Food Pun
Spherification was a technique originally pioneered by Unilever as part of a drug delivery process in the 1950s. They wanted to make little beads of medicine with a thin skin to keep the inner liquid from slopping all over. Once the skin was punctured, the beads would squish, or pop, or burst, or explode - whatever word would make poor, sick people feel best about putting them in their mouths. Around 2003, Ferran Adrià, a celebrated chef, thought this sounded delicious, and brought the technique over to food science. As a result, almost any liquid thing, and quite a few solid things, have been turned into quivering balls of goo ready to burst in people's mouths and leak down their uncontrollably spasming throats.
Alcohol is a popular spherified food, as a little in one's system helps people face the prospect of eating more gel beads. One could make a martini in bead form - complete with bead olives, which consist of olive juice pureed and gelled up. Fruit juices are also often spherified, despite many of them coming in spheres to begin with. But how is it done?
The entire unfortunate experience is due to two compounds, sodium alginate and calcium chloride. Sodium alginate is a long polymer already in a great deal of foods. It's used in pie fillings and milk shakes as a thickening agent. Its long chains of sugars stretch through the medium and tangle together, making the liquid around it thick. Sodium alginate is harvested from the long strands of kelp that grow in the Pacific ocean. An important part of the extraction process is removing all the calcium from the string of alginates. Why? This allows the strings to move freely and independently of each other. Calcium ions react with the sugar molecules in the chains and bind them together. This could harmlessly loop one string, which wouldn't make too much of a difference. But when two strings, and then more, get attached to each other, the entire string tangle fuses and solidifies into a gel.
What spherification does is put back in what the manufacturers of sodium alginate take out. First, the food, whatever it is, is pureed until it's liquid. Then the calcium content of the food is determined. If the calcium content is high, adding sodium alginate will solidify the whole thing immediately. To high-calcium foods extra calcium chloride is added. To all other foods, sodium alginate is added. Then, as with all delectable meals, it's off to the centrifuge. The mixture gets centrifuged to remove any bubbles or impurities there might be in it. Once that's done, drops of the stuff are tossed into a bowl of liquid. If the food contains calcium chloride, the liquid will contain sodium alginate. If the food contains alginate, it will be tossed into liquid containing calcium.
Immediately, the process begins. The outer edge of the spherical drops is the front line. When the sodium alginates hit calcium ions, the ions bind the long strings together, until they form a kind of haphazard net of polymers. The outer layer of the gel solidifies before any of the inner liquid can leak out. Depending on the concentration of both chemicals, and the time spent in the 'bath,' the gel will either be a tiny skin, or an extremely firm layer. Even if the mix of chemicals is weak, the reaction will keep moving inwards, so the balls have to be whisked carefully out of the bath, put on a plate, and rushed out to be set in front of the strained smiles of dinner guests. Then there's just enough time to say, "Oh. You served me vegetable soup in cold, quivering ball form. How original," and it's down the reluctant hatch.
Better living through chemistry.
Top Image: Jlastras