Spherification is often held up as a poster child for modernist cooking, and with good reason. These liquid spheres, encased with a gel membrane, are a unique and amazing way to serve food.
At its most basic, spherification is the process of creating a gel around a liquid, forming a gelled sphere with a liquid center. It is one of the hallmarks of modernist cooking and one of the most attention grabbing techniques.
Spherification typically refers to spheres 6 mm to 30 mm (1/4" to 1") in diameter with a still liquid center. The smaller spheres burst like caviar when bitten and the larger ones release their liquid similar to an over easy egg yolk. If you serve these to guests who have never had them before they will be the most talked about part of the meal.
Spherification uses an interesting property of some gelling ingredients. These ingredients only gel in the presence of certain molecules, like calcium or potassium. In this book I use sodium alginate, an algae extract, in combination with calcium lactate, though there are many ingredients that will work.
If you take a liquid with one of these gelling ingredients in it, it will not start to gel until it comes into contact with those molecules. If it is placed into a second liquid containing those molecules then it will begin to gel the liquid, starting at the outside and moving inwards. Until this process is complete, the inside will remain a liquid, completely encapsulated in a gel sphere.
There are two main spherification techniques, direct spherification and reverse spherification, depending on where you put the gelling ingredient. If you add the ingredient to the flavored liquid it is "direct spherification" and if you add it to the setting bath, it is "reverse spherification".
I find reverse spherification easiest to use because you can freeze the liquid into spheres before gelling it and because the spheres stop gelling when you remove them from the setting bath.
There are several things to keep in mind when using spherification.
If you are not freezing the base before using it then you may want to thicken it slightly with xanthan gum. A thicker base will hold together better and keep its shape in the setting bath. Usually 0.1% to 0.4% xanthan gum will be enough to do the job.
Another variable is the thickness of the setting bath. If the flavored base is denser than the setting bath the spheres may sink to the bottom and form in non-round shapes. Thickening the setting bath to the same thickness of the flavored base will cause them to float, suspended, in the setting bath.
Some gelling agents, like sodium alginate, do not work as well with acidic ingredients. This is more of an issue in direct spherification and is something to be aware of if you are trying to make acidic spheres.
Many gelling agents can be heated before they melt, which means that spheres made from them can be heated as well. If you are planning on serving the spheres in a soup or on a hot dish pick a gelling agent that works well with it.
Please be careful serving spheres that are at high temperatures; they can cause severe burns since many people expect them to be cooler.
There are a few things needed to achieve spherification.
There are many gelling agents that can be used for spherification. In general, any gelling agent that requires specific ions to gel can be used. I usually turn to sodium alginate because it is very effective at both direct and reverse spherification. Once set, it also can be heated above the boiling point without melting, making it very versatile.
However, you can also use carrageenan, gellan, or even pectin depending on what you are gelling and the desired properties for the spheres.
In order for the gelling agents to gel they need to be in the presence of calcium or potassium. In order to supply this add calcium salts. There are several different ones but the most common are calcium chloride, which has a bitter taste, and calcium lactate, which I prefer to use.
Some liquids you want to use in spherification might already contain calcium or potassium ions. These liquids will not work as they are because the gelling agent will gel instantly. In these cases you need to use sequestrants. Sequestrants basically tie up all the calcium and potassium ions in a liquid so they can't react with the gelling agent. You can then use the liquid for spherification like you normally would.
Some common sequestrants are sodium citrate and sodium hexametaphosphate; they are usually used in a 0.1% to 0.2% ratio.
There are two main types of spherification, direct and reverse. At the most basic level, in direct spherification the gelling agent is in the base and in reverse spherification it is in the setting bath. While it seems like a minor difference it causes a few changes in how they work. This is because in both methods it is always the gelling agent that gels, never the liquid containing the ions.
The location of the membrane is affected by the type of spherification used. In direct spherification the gelling agent is in the flavored base so the membrane grows inward as the ions reach the gelling agent. For reverse spherification the membrane grows outward, into the setting bath. This means that the membrane from direct spherification is flavored like the liquid, while in reverse spherification it is flavored like the setting bath.
What happens when the spheres are removed from the setting bath is also affected by the type of spherification used. Spheres made with direct spherification will continue to gel until eventually becoming solid. This is caused from the flavored base containing not only the gelling agent, but also now some ions. These ions continue to gel the liquid so the spheres must be served in a timely manner.
In reverse spherification the gelling agent is in the setting bath so once the spheres are removed there is nothing else to gel. This means these spheres can be stored for several hours, or even overnight, before serving.
The flavor of the membrane will depend on the type of spherification used. In direct spherification the membrane will be made of the flavored base so it will have a more pure flavor. In reverse spherification the membrane is made up of the setting bath. Sugar is often added to the setting bath to make it sweeter.
I like to start with reverse spherification because I find it much easier to do. In reverse spherification you combine a calcium salt, typically calcium lactate with the flavored base you want to turn into a sphere. You then freeze this liquid in hemispherical or spherical molds, about 25 mm (1") in diameter.
Technically, you don't have to freeze the liquid to make the spheres; it just makes the process much easier. When frozen, the spheres have no chance to break apart. It also allows you to create spheres of a uniform size more easily.
Once the base is frozen you make the setting bath. This is done by combining water with the gelling agent and sometimes some sugar. In reverse spherification I prefer using sodium alginate.
The frozen spheres of base are then placed into the bath for 1 to 5 minutes, depending on the thickness of the membrane you want. Make sure the spheres are not touching or they will fuse together.
I recommend starting with one sphere at a time to test out some different setting times. That way you can see which one works best for your specific purpose. In general I've found these times work well:
Once the membranes have set the spheres are removed and rinsed in a water bath. This bath can be warm or cold, depending on the temperature you would like to serve the spheres. At this point the spheres are ready to be served.
The spheres can be stored for several hours or even overnight in liquid. However, the liquid can leech out some of the flavor so they shouldn't be left in plain water for more than 15 to 30 minutes. If you know you will be storing them for an extended period of time I recommend setting aside some of the liquid used in the base, before the calcium is added, and storing the spheres in it.
You can also place the finished spheres into a whipping siphon, with some reserved calcium-free liquid. Charge it and let it sit for several hours to carbonate the spheres.
For the flavored base a ratio of 1.0% to 3.0% calcium lactate is typically used with a setting bath of 0.4 to 0.5% sodium alginate.
Making spheres with direct spherification takes more practice than with reverse spherification. Both the setting bath and the flavored base are liquid when you combine them so it takes better technique to create spheres.
One thing to keep in mind when working with direct spherification: many bottled juices have potassium or calcium added to them which will cause the flavored base to set before it is added to the setting bath. For these juices, and other liquids with calcium or potassium present, you will have to use a sequestrant or use reverse spherification.
To make spheres with direct spherification you combine the gelling agent with the flavored base. You then prepare the setting bath by combining water with a calcium salt such as calcium chloride or calcium lactate.
To make the spheres you fill a spoon with the base and hold it just above the setting bath. Pour the base off the spoon and into the setting bath.
It should develop a membrane relatively quickly, about 1 to 3 minutes, and can then be removed. The sphere needs to be rinsed off in water to remove the setting bath from the outside.
At this point it is ready to be served. It can be held for a few minutes, about 10 to 15, depending on the size of the sphere, but it will continue to gel until it eventually becomes solid. Some people will heat the spheres near boiling to prevent further gelification from occurring.
There are several gelling agents you can use for direct spherification.
For direct spherification a 0.5% to 1% sodium alginate base is used with a 0.5% to 1% calcium lactate setting bath.
For direct spherification a 1% to 3% iota carrageenan base is used with a 4% to 6% calcium lactate setting bath.
Caviar are just small spheres. Because spheres that touch stick together in reverse spherification, it isn't very effective for making them. Direct spherification is usually used.
The initial steps to making caviar are the same as for making larger spheres. You first make the flavored base and mix in the gelling agent. Next, you prepare the setting bath with a calcium salt.
To make the caviar, drip the base into the setting bath and let them set for 30 to 90 seconds. Remove them from the setting bath and rinse them off before serving them. There are many ways to facilitate the dripping. You can use a plastic syringe, squeeze bottle, or eye dropper. Some people dip their finger tips in the liquid and lightly shake it off into the setting bath.
For larger quantities of caviar you can use a rapid caviar maker, which is a small box with 50 to 100 holes for the base to drip out of; this greatly speeding up the process.
The ratios for making caviar are the same for direct spherification.
For caviar, a 0.5% to 1% sodium alginate base is used with a 0.5% to 1% calcium lactate setting bath.
For caviar, a 1% to 3% iota carrageenan base is used with a 4% to 6% calcium lactate setting bath.