In, I explained the odd phenomenon of spherification, where two chemicals in water combine to form a gel that creates a sphere of water, making an edible water bottle. Now, I'll show you how to create your own edible spheres of water.
To create small spheres, you will need two basic ingredients: sodium alginate and calcium chloride or calcium gluconate lactonate, depending on which type you try to make. Because modernist cooking is popular with home chefs, all three of these are readily available: I bought enough of these chemicals from Amazon to make many thousands of spheres. You don't need a lot of these chemicals either: I created all of the recipes in this column with less than $40 worth of these chemicals.
Basic spherification: Creating small spheres
The first technique is good for creating small spheres from most liquids, creating globules that resemble caviar. This can be used for liquids such as many fruit juices and drinks. In the photos that accompany this article, I used colored water.
1 -Dissolve 0.5 gram (0.02 oz.) of sodium alginate per 100 grams (3.5 oz.) of the liquid that you want inside the sphere. This is the hardest part of the process, as the alginate sometimes doesn't want to dissolve. The best way I found was to use cold water, then stir the liquid and add the alginate slowly while stirring. You probably won't be able to get rid of all the lumps, but keep stirring until they are as small as possible, then cover the liquid and leave for an hour or so. At this point, the alginate lumps should have dissolved, and any bubbles in the mix should have risen and popped.
2 - Dissolve 0.5 grams (0.02 oz.) of calcium chloride in water, preferably distilled. Put this mixture into a bowl or dish.
3 - Put clean (again, preferably distilled) water into a second bowl or dish. We will use this to rinse off the finished spheres.
4 - Drip the alginate mix into the calcium chloride mix one drop at a time. I found the easiest way to do this was to use a small eyedropper, but you can use a small spoon or a straw.
5 - As each drop hits the calcium chloride mix, it will form a gel skin and float to the surface. Leave the small spheres in the mix for between 30 seconds and a minute.
6 - Using a spoon, remove the spheres and rinse them in the clean water. This stops the gelling process. Place the spheres on an absorbent surface to dry, and serve.
This technique is simple to do and can product a lot of spheres quickly. If you want to produce a very large number of spheres for a dinner or drinks party, chefs use a device called a caviar maker, which creates multiple drips at once. If the small spheres are too fragile, or you are trying to make larger spheres, leave them in the calcium chloride mix for longer, as the longer they are in there, the thicker the gel coating will become. But be careful -- too long and all of the liquid gets gellified.
The downsides of this technique are that the liquid gets a slightly gummy texture from the alginate, and it works only for small and medium-size spheres: if you make larger ones, the gel skin will break easily because the membrane is weak. Fortunately, a tweak to this technique gets around this issue.
Reverse spherification: Creating larger spheres
To produce larger, tougher spheres, we need to alter the way we create the spheres. Instead of adding alginate to the liquid to be spherified, we add the calcium ions to the liquid, and then put this into an alginate bath. Instead of calcium chloride (which is very salty), we use calcium lactate gluconate, which is tasteless. Again, this is also easily acquired from Amazon, as well as most health food stores. In the photos below, I made spheres using colored water, but the technique should work with most liquids.
1 - Dissolve 0.5 gram (0.02 oz.) of sodium alginate per 100 grams (3.5 oz.) of filtered (and preferably distilled) water. Most of the time, 300 to 400 grams (0.3 to 0.4 liter) of water should be enough.
2 - After the alginate mix is bubble-free, dissolve 2 grams (0.07 oz.) of calcium lactate gluconate into each 100g (3.5 oz) of the liquid to be spherified. This chemical dissolves much more easily than the alginate; a quick stir or two should be enough.
3 - Use a spoon or scoop to measure out as much of the calcium-infused mix as you want in each sphere. Start small, using a teaspoon or something similar.
4 - Tip the calcium mix into the alginate bath quickly and smoothly. This takes some practice, but you want to get all of the mix into the alginate as quickly as you can, so it doesn't spread or flow.
5 - Leave the sphere in the alginate bath for about a minute. You should see the gel form on the surface of the sphere.
6 - Using a spoon, remove the sphere and rinse in a dish of clean water, as above. Place the sphere on an absorbent surface to dry, and serve.
The resulting spheres can sometimes come out misshapen. Much of this is down to how you add the calcium-infused mix to the alginate bath: if you do this too slowly, the liquid flows and forms lumps and other protuberances. This can also happen if the liquid you want in the sphere is more dense than water, as the liquid will sink and stick to the bottom of the bowl. Professional chefs get around this by adding xanthan gum or similar substances that bind the liquid and change its density. Mostly it just takes practice, figuring out how to pour the liquid in at the right rate to create a smooth sphere.
Another way to get more perfect spheres is to add an additional step, freezing the calcium mix in either a spherical ice mold or a dedicated spherification mold. To do this, pour the calcium mix into the mold and freeze it between steps 2 and 3 of the process above. The frozen sphere holds its shape, and the gel surface forms as the surface of the sphere melts, freeing the calcium ions. If you then rinse the sphere and let it defrost, you'll get a near-perfect sphere filled with your liquid.
That's the basics of spherification. In my next column, I'll experiment with a range of drinks and liquids, looking at what effect the chemistry of various foods has on the process. In the meantime, why not experiment yourself and post the results in the comments below?