Substitute agar-agar for gelatin in pudding

Yes, there are several vegetarian fondant recipes using agar. Most tend to substitute it for gelatin in equal amounts.

Keep in mind two things:

• Agar has a much higher melting point and sets firmer than gelatin, so the resulting icing will be less "melty".

• The hydration process is completely different from gelatin. It doesn't bloom; it needs to be dispersed in cold/warm water and then heated all the way up to 90° C with constant agitation.

I'd recommend that you include the glycerin in any agar-based fondant recipes - they'll make it a lot easier to work with. Some gelatin recipes leave it out but IME you need it more for agar.

The difference between activating them is important if you want to use gelatin instead of agar. Gelatin is made of proteins and peptides and agar is a polysaccharide.

Gelatin should not be boiled, because it breaks down. Agar needs 95 deg C to dissolve, so usually it is simply boiled. This means, that if your receipe calls for boiling the agar with stuff you want to gel (e.g. fruit), you have to add gelatin later, when all the boiling is finished, but the mixture is still hot enough to dissolve the gelatin.

Also, agar will work on some fruit, that prevent gelatin from geling, like pineapple or kiwi. If you want to use these fruit with gelatin, you have to boil them (or so they say - I have access to agar, so I never tried gelling boiled pineapple with gelatin).

Oh, and about the proportions: 1% agar as stiff as a jelly bear, 0,5% agar is as stiff as a normal jelly. One teaspoon agar weighs 3g, so it will make about 600ml of a jelly.