I find that I get inconsistent results when I use gelatin. Even for the same recipe, sometimes it will come out softer or firmer than other times. What is happening?--Sara
Gelatin is a protein-based thickening agent used primarily in making desserts, aspics and jellies. It comes in a powdered form which is easy and convenient for home cooks, and in a sheet form which is more often used commercially. It can be tricky to get good results though, for a number of reasons.
First, despite the assurances of the manufacturers of the envelopes of gelatin which state that they are supposed to contain just enough to thicken two cups, never trust the contents to be measured accurately. In my own kitchen, I have found up to about a 25% variation in the amount of gelatin in a pouch. That is enough to make a difference in the result.
Gelatin should be soaked for about five minutes in a cool liquid first, before being heated or combined with hot liquids. This soaking allows moisture to penetrate into the granules so that they will dissolve more readily in heat. If you pour powdered gelatin directly into a boiling liquid, it will form clumps that take longer to dissolve. Gelatin that remains undissolved results in a grainy texture and does not help to thicken the dish.
According to Corriher, gelatin loses some of its thickening power when boiled. It should be heated only until fully dissolved, or should have the hot liquids added to it off heat, depending on your recipe.
Also, other ingredients such as sugar and salt can affect the result. Salt will interfere with the bonding of protein molecules, making a weaker product, while sugar will attract water away from the gelatin molecules, causing a firmer result.
If you are using fruit, be sure it is not one that can affect the setting of gelatin, such as raw pineapple or kiwi (see Jellied Fruit Salad Won't Set).
Acids found in fruit juices, wines and other ingredients can also affect the result by making the gelatin proteins less likely to bind together, by creating an electrical charge on the molecules which force them to repel each other.
Finally, when cooling jellies or other foods containing gelatin, resist the temptation to put it in the freezer, as the gelatin molecules need to move freely in the cooling liquid so that they can become entangled. Too fast of cooling can prevent this from happening. According to Harold McGee, jellies that are snap-chilled will regain a more normal consistency after a few days.
While not as fussy as some ingredients, gelatin does require some care in measurement of the ingredients used in preparing any dish.
For fans of KitchenSavvy, our local paper, the Saskatoon Star Phoenix, recently ran an article titled "In the Kitchen with ... Dave and Patricia Katz". This is the most recent installment of their In the Kitchen series. In the article you can find five of our favorite recipes including Pissaladiere, which is already posted here, and Shrimpniks, a lemon-butter-garlic shrimp recipe created in tribute to Cousin Nik's restaurant, which we used to like going to before it went out of business.