This week, I'm making good on a promise and discussing gelatin clarification. While gelatin filtration -- the use of gelatin to clarify and concentrate flavorful liquids from a dizzying assortment of sources -- isn't exactly new, it's also not something with which most home cooks are familiar. That's a shame, really, because it's utterly simple, almost boundlessly useful, and more than a bit magical.
I first learned about the process a few years ago, reading one of my favorite food blogs, Ideas in Food. The authors of that blog use gelatin clarification to make crystal-clear stocks -- call them consommés if you want to be fancy -- out of an endless variety of ingredients and combinations thereof. Parmesan stock? Check. Horseradish stock? Brown butter-soy-Tabasco stock? You bet. It seems as if these chefs have used gelatin clarification to render virtually anything edible or imbibe-able into an utterly clear, vividly flavorful distillate.
The process itself is ingeniously simple. Basically, you create a liquidy puree of whatever ingredient or ingredients you want to clarify, add gelatin, and freeze. Once frozen, you place the frozen gel in cheese cloth or some other straining medium, suspend it over a bowl or other container, and place it in the refrigerator. Two to three days later, you will have a bowlful of crystal clear, purely flavored liquid.
It works through a process called syneresis, wherein gel matrices expel their liquid phase, in this case, using a controlled temperature environment and the nature of frozen water to aid the process. As the gelatin sets in your puree, particulate matter gets suspended in a microscopic gelatin net. When you freeze the mixture, ice crystals form and puncture the matrix, creating channels through which liquid can efficiently escape the gelatin structure as it thaws slowly in the refrigerator. The particles stay behind. Any fat in the mix stays solid, thanks to the cold temperature.
This time around, I made a carrot-ginger stock, pureeing five or six carrots with a small knob of ginger and enough water to make it liquidy. You don't even have to peel the ginger, as the fibers will remain suspended in the gelatin as it thaws. In reality, you only need a small amount of gelatin (I used unflavored, powdered gelatin) to make this work, nowhere near the amount you would use for a gelatin dessert. I got lazy and just dumped a whole envelope in. I think the preferred ratio is something on the order of .5 percent gelatin by weight.
Over the next three days, my stock wept from the gel, drip by slightly golden drip. The fact that I added more gelatin than necessary slowed the process, and the slowed process made me impatient. I made a fatal error. I pressed the gel, and a bit too hard. A gentle squeeze didn't hurt, and helped speed things up a bit. I knew better, but I really put some weight on it, and I ruptured the gel too much. Some of the trapped particulates escaped, clouding my otherwise gorgeously clear liquid. I was rather upset with myself. Don't make that same mistake.
I still haven't decided what to do with it. I had planned to gently poach some sort of fowl, dice it very cleanly, and serve it as a simple carrot-ginger consommé, garnished with the diced bird. Now, I may re-clarify it. Or, I just might use it as a cooking medium, perhaps as the poaching liquid for something.
Next time, I'll do it right, and let patience win. I have plans on parmesan and pork stocks clarified this way, to use as the liquid component in a carbonara-themed sabayon. I'll let you know how it turns out.