The Reverse Spherification technique consists of submerging a liquid with a mixture of calcium gluconate and calcium lactate in a bath of sodium alginate. There is also a variation of this technique, Frozen Reverse Spherification, that reduces preparation time, does not require practice and results in perfectly shaped spheres of consistent size.
Pros of Reverse Spherification
- Reverse Spherification is more versatile than Basic Spherification as it can make spheres with almost any product. It is best for liquids with high calcium content or alcohol content which makes them great for cocktails and dairy products like cheese, milk, cream and yoghurt.
- The resulting sphere is long-lasting and can be stored for later consumption. Contrary to Basic Spherification, the process of jellification can be stopped when the sphere is removed from the sodium alginate bath and rinsed with water. This is very convenient when entertaining friends as you can prepare them ahead of time. This also allows you to macerate the spheres overnight to add some extra flavor (e.g. in aromatized olive oil or truffle water).
- Reverse Spherification results in a sphere with a thicker membrane than with Basic Spherification. Thanks to this, the resulting spheres can be manipulated easily, they conserve their shape better when plated (spheres produced with Basic Spherification flatten and acquire an orb or egg yolk shape when plated) and can be used in more ways (e.g. as fillings in sponge cakes or mousses).
- Jellification still occurs when the main ingredient liquid has some acidity. This is because in Reverse Spherification the jelling process occurs on the surface of the sphere as the sodium alginate fails to penetrate it. A translucent layer of gel is created around the main ingredient. In Basic Spherification, the gelling process occurs internally and has the color of the main ingredient.
- The main ingredient consistency and flavor is not altered by the addition of calcium gluconate and calcium lactate as they have no discernable flavor and dissolve in liquid without altering its density. This is the reason why in Reverse Spherification we don’t use calcium chloride which is very salty.
Cons of Reverse Spherification
- The thicker membrane of these spheres is more evident in your palate. You still get the “pop” sensation but in addition to the liquid you also feel the solid jelly in your mouth.
- The sodium alginate bath needs to rest for 12-24 hours before using it for Reverse Spherification to eliminate the air bubbles created by the process of dissolving the sodium alginate with the immersion blender.
- It is a little harder to get a perfect sphere on the plate with Reverse Spherification than with Basic Spherification. You are pouring the main ingredient into a viscous bath, the spheres tend to stick to each other if you don’t separate them in the bath and the thicker membrane maintains the shape better which is great if you were able to create a perfect sphere but not if your spheres are “deformed” (for optimal results read "10 Tips to Create a Perfect Sphere"). Frozen Reverse Spherification solves this problem if the main ingredient can be frozen. Learn about Frozen Spherification here.
- Reverse spherification is not great for making caviar as the main ingredient needs to be thickened to be able to penetrate the dense sodium alginate bath and cohere into a sphere. (for optimal results read "7 Tips for Making Spherification Caviar")
Preparing the Bath for Reverse Spherification
Blend the sodium alginate in 1/3 of water with an immersion blender until it is completely dissolved. Keep in mind that the sodium alginate is hard to dissolve in water and this process may take a few minutes. Then add the rest of the water and keep in the refrigerator for 12 to 24 hours to remove the air bubbles created by the blender.
Preparing the Main Ingredient for Reverse Spherification
Add the calcium gluconate and calcium lactate to 1/3 of the main ingredient to be used. Blend with an immersion blender until it is completely dissolved. Then add Xanthan to thicken the liquid and blend one more time. Increasing the density of the liquid helps form the spheres as the alginate bath is quite dense. Add the rest of the main ingredient and let it rest for 1 hour so that it loses part of the air created by the mixer.
Creating the Spheres
Now grab the syringe (if you are making caviar) or the measuring spoon of the desired size (if you are making ravioli, gnocchi, etc.) and carefully pour the preparation in the sodium alginate bath making sure the spheres don’t touch each other or they will stick. Wait for the time indicated in the recipe and carefully remove the sphere from the sodium alginate bath using a slotted spoon and rinse it in clean water.
I recommend you always start with one sphere first to adjust the pouring process and the time in the bath. If the sphere membrane is too subtle and the sphere easily breaks when handling it with the slotted spoon carefully or when plating it, extend the time in the sodium alginate bath until you get the desired strength. Keep in mind that the thinner the membrane the better experience people are going to have when eating it.
Consume the spheres or store them in a sealed container in the fridge. If you like, macerate them for a day in olive oil, truffle water or your favorite liquid.