Have you ever made chocolate mousse at home, only to have it deflate a few hours later in the refrigerator? I have. But there’s a way to keep this from happening. What’s the secret? Gelatin.
Gelatin is a tasteless thickening agent derived from collagen, a type of protein that gives structure to desserts, gummy candies, and old-school French food (think aspics filled with meat and fruit or vegetables). Most people, however, would be hard-pressed to remember the last time they ate aspic (much less wanted to eat it), so it’s more likely to be encountered in puddings, parfaits, icebox pies, marshmallows, ice cream, and mousse. It is also found in many of our medicines; the shells of liquid-gels and other hard and soft capsules are generally made out of gelatin. (Photo courtesy of flickr/katerha)
Gelatin is derived primarily from pig skin, cow bones, and cow hides, although it can be derived from plant-based sources as well, such as seaweed. Recently, Chinese scientists have even found a way to make it by inserting human DNA into yeast cells. The researchers argue that the advantage to producing gelatin from human DNA is that it eliminates the risk (however slight) of animal-based diseases, such as mad cow disease, from contaminating the food supply. Coming soon to the baking aisle.
A trip to the store today, however, will reveal two main types of gelatin for sale — the more common powdered gelatin, which comes in ¼-ounce envelopes; and leaf gelatin, which look like thin, clear sheets. A little goes a long way: One envelope of powdered gelatin (or four sheets of leaf gelatin) is sufficient to thicken two cups of liquid. Leaf gelatin takes a little longer to dissolve, but is essentially the same product, just in a different form. It is frequently used in European recipes. Whichever type you decide to use, though, there are some useful rules of thumb to keep in mind.
Gelatin should always be soaked in cold water (or depending on how you’re planning to use it, another liquid, such as cream), for three to five minutes before use. Otherwise, once you start cooking the gelatin, it won’t dissolve properly. At the same time, however, you never want to boil it, as this will denature the proteins, as they say in science-speak, and you can never put those back together again, kind of like taking apart a Rubik's cube. In other words, you’ll ruin the gelatin, and it won’t work anymore.
Certain types of fruit can also keep gelatin from working properly. Fruits such as fresh figs, guava, kiwi, papaya, and pineapple need to be cooked first to break down the substances which keep the gelatin from setting. And whatever fruit you decide to stir into your dessert, make sure to wait until it’s partially set, so that it doesn’t accumulate at the bottom. (Photo courtesy of flickr/Nathanael B)
So, back to that chocolate mousse. How does gelatin come into play in this dessert? You’ll need to stir pre-soaked gelatin into the melted chocolate after it has cooled slightly (it shouldn’t be room temperature, but it shouldn’t be boiling hot, either). Then, fold in the whipped cream in two batches, making sure not to overwork it. After that, your mousse will be invincible. Well, almost.