The typical process for reverse spherification is actually pretty easy. You start with a non-acidic liquid, in this case fresh mango juice. You then blend in calcium to the liquid, we used calcium lactate.
To make the spherification process easier we took a page from the Alinea cookbook and froze the mango juice in spherical ice molds. Freezing the liquid makes it much easier for the juice to keep its form when you actually spherify it.
Once the juice is frozen you prepare the sodium alginate bath by blending the sodium alginate and sugar into water with an immersion blender. Warm the alginate solution until the sugar is completely dissolved and then strain it into a bowl.
Place the frozen mango juice into the alginate bath, making sure they are not touching. Depending on how thick you want the membrane to be you can leave it anywhere from 2 to 5 minutes. Once it is set remove them from the bath and rinse them off in water. You can then hold the spheres in water until you are ready to use them. They should stay spheres even when heated up to about 300°F / 148°C but prolonged heat can cause them to break down.
For more examples of spherification you can read the excellent Alinea cookbook.
If you like this recipe you can get more than 80 other recipes from my book Modernist Cooking Made Easy: Getting Started. The book covers many of the popular modernist techniques such as gelling, spherification, and foams. It also explores modernist ingredients like agar, sodium alginate, tapioca maltodextrin, and xanthan gum. It is all presented in an easy to understand format and I think it's the best way to learn about modernist cooking.
Also, if you are just getting started experimenting with molecular gastronomy and modernist cuisine then I highly recommend one of these molecular gastronomy kits. They have everything you need to do many different dishes.
All measurements by weight.
Combine the mango juice and calcium lactate in a bowl using a hand blender. Pour into hemispherical or spherical molds and freeze.
Combine the water, sugar, and sodium alginate in a sauce pan and blend with an immersion blender. Heat until the sugar dissolves and then strain into a bowl through a chinois.
Fill a bowl with cool water.Take the mango juice spheres out of the ice tray and place into the alginate bath. The amount of time you leave them in will depend on how thick you want the membrane and how large the spheres are. I recommended starting with one sphere at a time and test out some different times to see which time works best for your purpose. In general though you can do:
You can also leave the spheres in for an extended time, around 7 to 10 minutes, and they will develop a super thick gel with a small liquid center which reminds me of some Asian candies I've had.
Remove the mango raviolis from the alginate bath and place into the bowl of cool water, rinsing them gently.You can hold the spherified mango ravioli in this state for several hours. They can be served cold or heated up to 300°F / 148°C (though please don't serve them at a temperature much above 100°F / 37°C or you can cause severe burns).