To continue my discussion on the art of molecular gastronomy, this week I look at the technique of creating caviar type dishes known as spherification. With this technique, you can make breathtaking creations using just about any liquid and a little science. Two of the main chemical compounds used in the process are sodium alginate and calcium carbonate. While these two items may not be something you would normally find on a grocery list, they are quite common. In order to understand how this chemical reaction leads to the end result, we need to have a further understanding of the ingredients themselves.
Sodium alginate is a flavorless gum that has an empirical formula of NaC6H7O6. It is the sodium salt of alginic acid and is found in the cell walls of brown algae. Sodium alginate has many uses within the food industry to increase viscosity as well as its use as an emulsifier. It is combined with calcium lactate when used in molecular gastronomy for the spherification techniques. One common product to use sodium alginate is cocktail olives. By injecting pimento juice and alginate mixture into cocktail olives as the stone is removed, the juice is gelled by the calcium present within the olive and thus gives the impression of an actual slice of pimento.
Calcium carbonate is a chemical compound commonly found in the shells of marine organisms, snails and eggs, among other things. It is used for just about everything from water softening to industrial construction and even the oil industry. For the food industry, calcium carbonate in mainly used as an acidity regulator as well as a firming agent in canned food or bottled vegetable products. In the case of our subject, it is used as a firming agent to complete the spherification process.
Now that we have a basic understanding of what spherification is and what chemical components are needed to achieve it, we can discuss the reasons for this technique and how to accomplish it.
Why would we use this technique? This answer is simple; it’s”wow” factor can transform a simple dish into something extravagant. As I noted before, with this technique you can transform almost any liquid into a stunning serving of caviar that has a very large flavor profile. As for how this is accomplished, it is really quite simple once you do the math. Getting the right amounts is critical for the process to work correctly.
You can begin with just about any liquid with the exception of those with large amounts of free calcium such as milk products. Too much calcium will cause the alginate to gel too quickly and spheres won’t have time to form. Good liquids to begin with would be lemon or lime juices, something with a higher pH level to help the gelling process. With you liquid selected and very cold, blend in 0.5% of the liquids weight in sodium alginate. Once blended, allow the alginate to hydrate completely. This can take from a few minutes up to a couple of hours. After it is fully hydrated and back to a liquid form, make sure there are no air bubbles left within the mixture before you continue.
The next step is to prepare the calcium bath which is done by simply dissolving calcium salt or calcium chloride in water. Once ready, use a syringe to drop the liquid into the bowl. The height at which this is done will dictate the size and shape of the spheres. The bowl should also be deep enough to allow the drops of liquid to fall a second or two before hitting the bottom. After coating the bottom of the bowl with the spheres, gently swirl the water to help the outer membrane set. Drain and rinse the spheres once set and serve immediately for the best presentation and flavor.