A few years ago I started making a Good Eats inspired cranberry granita whenever November rolled around. This quick, easy dessert is great to have around not only for its convenience but for its luxurious mouthfeel. The large, pectin-infused ice crystals melt slowly and coat the tongue with the tart cranberries flavors cut by the sweetness of the sugar and brightness of the lime zest. As recommended on the show, the granita also makes a damned fine cocktail. Once the crystals melt they provide a complex cranberry flavor far exceeding that of any cranberry juice, not to mention the added body and texture.
But is there a compromise between the two service options? Tequila and Cointreau would play excellently with the flavors in the granita, but adding the spirits directly to the crystals would only accelerate the inevitable melting. I needed a way to contain the spirits, keeping them separated from the granita until service. A technique from the oft maligned molecular gastronomy offered a possibility; armed with some sodium alginate and calcium lactate samples from Jeff of Cooking For Geeks I started playing with spherification.
A derivative of seaweed, alginate doesn't do much more than thicken liquids. When the alginate solution comes in contact with the calcium lactate, however, the thickening is dramatically enhanced. Submerged in a calcium lactate solution, a weak alginate solution would form a thin skin around a liquid core. Made weak enough, the delicate skin is just strong enough to contain the liquid until popped in the mouth.
That's the theory, anyways. Use too much alginate and the liquid becomes too thick and the skin too tough, rendering the final pearls awkwardly chewy. Recipes trawled from the internet lack any consistency, so the final ratios had to be left to experimentation. Even with working proportions, forming the spheres themselves is nontrivial. Creating small caviar isn't too hard, but larger pearls takes some clever technique. The delicate membranes then require careful handling, lest they burst prematurely.
It took a few iterations, but I eventually settled into a successful recipe and developed sufficient technique that I could consistently produce large, fragile pearls well suited for the granita. I was using an old bottle of cheap blue curacao for testing, and the bright, contrasting color proved useful for illustrative purposes. Any real application would likely feature translucent pearls hiding within the red crystals.