THE SPHERIFICATION TECHNIQUE
Spherification is a culinary technique widely used by modern chefs, being a subcategory of what is usually called molecular cuisine. It basically consists of presenting a food in the form of spheres or ovals that have a soft texture on the outside and contain liquid on the inside, producing a curious and pleasant sensation in the diner when they are placed in the mouth. The outer layer of the sphere is a jelly formed by the reaction of two compounds, usually sodium alginate on the one hand, which is a natural thickener from seaweed, and a calcium-rich solution on the other. When these two compounds come into contact, a layer of gelatine develops that is strong enough to form spheres as large as the yolk of an egg. It is common to try to emulate the shape of caviar by making spheres the size of salmon roe. Other shapes are also possible. It is possible to make spheres from virtually any liquid food, whether sweet or salty as long as its pH is slightly acidic but not lower than 3.8 pH. The resulting sphere will be stable for quite some time exposed to air or immersed in another liquid. We only have to handle it carefully so as not to break it and it is usual to serve it to the diner on a spoon so that he does not have to handle it to put it in his mouth.
HOW IT IS MADE THE SPHERIFICATION TECHNIQUE
We have already explained that spheres or spherifications are obtained by reacting two solutions, one containing sodium alginate and the other rich in calcium. There are two spherification techniques, respectively called basic or direct spherification and inverse spherification. The first is achieved by mixing the alginate in the solution that we are going to eat (a juice, a puree, a cream...) and on the other hand by creating a solution of water with calcium chloride or similar that will act as a bath where the spheres are going to be shaped. Both separate solutions must be mixed very well, preferably using an electric mixer, and must be left to stand for several hours and it is advisable for them to be cold (from the fridge). To make "yolks", fill a spoon with the juice+alginate mixture and carefully introduce it into the water+calcium chloride solution. Immediately the outer layer of our juice will solidify on contact with the calcium chloride solution. We wait a few seconds and with the same spoon or a small skimmer we can remove the spheres, briefly dip them in a clean water bath and they are ready to be presented and eaten. To make small spheres (caviar), use a large-mouthed syringe or a kitchen bottle filled with the juice solution and drop drops of the juice into the calcium solution. The result is small spheres very similar to caviar roe. There are also special systems that allow multiple spheres to be created at the same time and are called caviar kits.
But what if our food is itself a calcium-rich substance, such as a dairy product, broccoli or olives for example? In this case we will use reverse spherification which simply consists of using alginate to create the bath. From here, the procedure is identical to basic spherification and consists of introducing our juice with a spoon or syringe into the alginate-water solution. If the calcium content of our juice is not high enough, it can be reinforced by adding calcium gluconolactate.