A number of fruits such as kiwis, figs, papaya or pineapple contain in their cells protein digesting
enzymes. These enzymes will digest the gelatine into small parts, preventing its ability to form a gel.
When you want to make a gel with such fruits, use instead non protein gelling agents, or heat the fruits
or fruit juice, so that the enzymes are “denaturated”, i.e. they become inactive.
Agar agar is a gelling agents extracted from a red seaweed. It exists as long molecules made up of the
How it works
Agar agar needs to be heated in the liquid which is to be gelled until boiling point is reached. Once the
liquid is removed from the heat, the long molecules of agar agar ,and agar agar will start to lose
energy and will line up and form a network that traps the liquid molecules present, in a similar way to
gelatine. A gel made with agar agar will take about an hour to form.
Agar agar based gels can be heated up to about 80°C before they will melt. This has useful
implications in the kitchen because it means that cubes of an agar agar based jelly can be served in a
hot aromatic liquid (like a stock), or else sheets of the jelly can be used to make small raviolis which
can be served warm.
However, as well as a high melting point having advantages, it has the major disadvantage that it will
not melt at mouth temperatures – so will not have the same mouth feel affect as gelatine based jellies.
Agar agar based gels are also thermoreversible – they will melt on heating, but will reform on cooling.
The recommended concentration to use to make a gel from agar agar is 1%.
Because an agar agar gel is thermoreversible, if the gel has not set, it can be heated up with some
extra agar, and the gel will form on recooling.
Because of this property, it is advised to use the smallest possible quantity of agar – if used in excess,
it imparts a slightly grainy texture to the gel. (If it does not set, it can be reformed).
Gels made with agar agar can be formed in the presence of salt, sugar, and acid (as long as the pH is