This jelly-like food was discovered in the mid-17th century in Japan and is made from varieties of red algae, small salt-sea organisms indirectly related to larger seaweed. Carrageenan, or Irish Moss, is a related Western product.
Essentially unflavoured, it comes as a powder or in flakes that must be boiled with a liquid, such as fruit juice or coconut milk. It sets rather more firmly than gelatine-based jelly and does not melt as easily.
Agar-agar provides the base for an infinite variety of highly coloured, shiny, curiously flavoured cubes, twists and strips sold by Japanese sweet and dessert shops. In the West it is used a vegetarian substitute for gelatine and so can also appear in more diluted form in ice cream or in savoury sauces, including soups. Its other major use is as a basis for growing laboratory cultures.
Specialty shops and online.
Choose the best
Unflavoured agar-agar is preferable as it gives more flexibility.
Dry and cool, it will last a long time.
Typically a small amount of dried agar-agar is added to a liquid, brought to a boil and then simmered for up to five minutes. On cooling it will set. This boiling will reduce the fresh, full taste of some ingredients; if you use undiluted, acidic fruit juices, up to 25% more agar-agar might be needed. A little experimenting will quickly show what proportions and thus what texture you prefer.
There are many uses for agar-agar, especially in vegetarian dishes. It can be used to make a well-behaved set jelly in vegetable or fruit terrines, for example, or for such simple ideas as beetroot in a fruit-flavoured vinegar jelly. Wine jellies might hold savoury or sweet ingredients, or a mixture, such as chicken and mango in muscat wine. Agar-agar will set all sorts of fruit purees, custards and creams too and can work as the basis of layers in sponges and other cakes where meat-based gelatin would not be suitable – a vegetarian raspberry jelly in a chocolate cake, perhaps?