Gelatin is made from animal by-products and is used to set liquids in desserts like pannacotta, mousse, jellies, unbaked cheesecake etc. The vegetarian option of gelatin is called agar-agar, known popularly as China Grass. To create your own desserts, it will do you good to learn the technique of using it. This will open a world of dessert ideas.
The basic method of using Gelatin:
As a rule, for 2.5 tsp of gelatin, use 3 Tbsp of cold water or go by the instructions in the recipe. Sprinkle gelatin powder over cold water and let it stand for 5 minutes. The gelatin powder will swell up and turn gel-like. Add this to the hot dessert and stir to dissolve the gelatin. If the dessert is not warm enough, heat gently over a double boiler till the gelatin dissolves. Heating gelatin for too long makes it lose its ability to set.
Thumb rule to determine the quantity of Gelatin:
About 2 1/2 tsp of gelatin can set 2 cups of liquid firmly. For soft and creamy texture, use the same amount of gelatin in 3 cups of liquid. Always remember that the softly set liquid is difficult to unmold. Gelatin dessert will take a minimum of 4 hours to 24 hours to set in the refrigerator.
The vegetarian equivalent of Gelatin:
Gelatin can be substituted by agar-agar in the same quantity as called for gelatin. For example, 1 teaspoon of gelatin is equal to a teaspoon of agar-agar.
Fruits which do not set with gelatin:
Fruits like pineapple, kiwis, ginger can prevent gelatin from setting due to the presence of protease enzyme. If the recipe calls for these fruits then please cook them before adding the gelatin. This will destroy the enzymes and ill help the fruit pulp/jelly to solidify.