Gelatin is derived from the bones of beef. Agar-agar, which is made from seaweed and is used a great deal in commercial food processing for thickening and as a stabilizer, is a common alternative. It is sold in many quality health food shops.
Five grams of powdered agar-agar or dried sponge seaweed sets 750 ml of liquid, but you will never achieve a firm set if your mixture is acidic, for example a mousse with citrus; or if a mixture contains chocolate or spinach. Always dissolve the agar-agar first, then boil it slowly for 15 minutes to activate the setting process. It sets at a higher temperature than gelatin, but the result does not melt so well in the mouth and feels different.
Another vegetarian product that can be used as a substitute for gelatin is Gelozone, which is made from locust bean gum, guar gum and carrageenan, or Irish moss. Follow the instructions on the packet for quantites, and always heat gently before adding it.
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