Agar

Agar is a gelling agent made from red seaweed. It is sold as a powder, flakes or bars, and it is the usual vegan and vegetarian swap for gelatin. It sets firmer and more brittle than gelatin, and it sets at room temperature instead of needing the fridge.

How to use it

1. Whisk the agar into cold liquid. Powder dissolves best. Flakes and bars need 10 to 15 minutes of soaking first.
2. Bring the liquid to a rolling boil and boil, stirring, for 1 to 2 minutes for powder and about 5 minutes for flakes. Agar does nothing until it has boiled.
3. Pour into molds. It starts to set as it cools to about 35 to 40°C (95 to 105°F), so work quickly.

About 2 g (1 teaspoon) of powder sets 250 ml (1 cup) of liquid firmly. Use less for a soft, wobbly set. Flakes are weaker, so you need about three times as much by volume.

To test the set, drop a spoonful onto a cold plate. It should firm up within a minute. If it is too soft, add more agar and boil again. If it is too firm, add more liquid and boil again. You can remelt agar this way, which you cannot easily do with gelatin.

Substitutes

Gelatin is the obvious swap, but it is not vegan, sets softer and melts in the mouth. Agar does not melt until about 85°C (185°F), so an agar jelly holds its shape on a warm day and feels cleaner and snappier to eat. Pectin works for jams but not for molded jellies.

Common mistakes

• Only warming the agar instead of boiling it. The jelly never sets.
• Using flakes in a recipe written for powder. The set is weak.
• Adding a lot of acid, such as lemon juice. Strong acid weakens the gel, so add more agar or stir the acid in after boiling, just before it sets.
• Expecting a creamy texture. Agar gives a clean, brittle set. For panna cotta, use a little less agar than for a fruit jelly.

In recipes

Agar is common in Japanese sweets such as yokan and in vegan coulis jellies and cheesecakes. Unlike gelatin, it sets fine with raw pineapple, kiwi and papaya, because their enzymes break down protein and agar is not a protein.