what is Agar?
| Name | agar (E406) |
| Origin | polysaccharide obtained from red algae (several species) |
| Properties, texture | thermoreversible, heat resistant, brittle gel; high hysteresis |
| Clarity | clear to semi-opaque |
| Dispersion | in cold or hot water |
| Hydration (dissolution) | > 90 °C; heating to boil necessary for gelling. |
| pH | 2.5-10 |
| Setting | 35-45 °C, rapid (minutes) |
| Melting | 80-90 °C% |
| Promoter | sugar; sorbitol and glycerol improve elasticity, stronger gel at higher pH |
| Inhibitor | tannic acid (counteracted by add. of glycerol); prolonged heating at pH outside the range 5.5-8 |
| Tolerates | salt, sugar, alcohol, acid, proteases |
| Viscosity of solution | low |
| Typical concentration | 0.2% will set, 0.5% gives firm jelly, [0.07- 3%] * |
| Synergies | locust bean gum (only with certain agar types) |
| Syneresis | yes (can be prevented by replacing 0.1- 0.2% agar with locust bean gum) |
recommend tips for agar:
- Addition of glycerol or sorbitol can prevent
dehydration of the gel - When replacing gelatin or pectin for gels,
use 2-3 and 10 times less agar
respectively - For "raw" preparations dissolve agar in
small quantity of water. Heat remaining
solution to 35-45 °C and mix with agar
solution - If left uncovered agar gels dry out, but if
immersed in water or other liquid it swells
and retains its original shape - A special property of agar is the large
difference between the gelling temperature
and the melting temperature. This is known
as hysteresis - The minute amounts of agar needed canbe difficult to measure. One trick is to makea 0.1x strength agar by mixing 10 g of agarwith 90 g of sugar. For a recipe that callsfor 0.5 g agar you then use 5 g of the 0.1xagar/sugar mixture. But keep in mind thatyou do add a small amount of sugar, sothis is not suitable in every recipe
- Agar alone forms brittle gels, but in
combination with locust bean gum elastic
gels may be obtained.
