Agar-Agar: The Seaweed Gel That Replaces Gelatin
Agar-agar, often just called agar, is a gelling agent extracted from red seaweeds such as Gelidium and Gracilaria. It's a carbohydrate, not a protein, so it's a vegan and halal alternative to gelatin. It sets firmer and at a higher temperature than gelatin, and its gels stay solid even when warm.
How agar gels
Agar is made mostly of agarose, long sugar chains that coil into double helices as they cool. Those helices bundle together into a network that traps water, turning liquid into a gel.
Its behaviour around temperature is unusual and very useful:
- It only dissolves in boiling or near-boiling water, around 90–100 °C / 195–212 °F.
- It sets as it cools to about 32–40 °C / 90–104 °F.
- Once set, it doesn't melt again until about 85 °C / 185 °F.
This gap between setting and melting temperatures is called hysteresis. It means agar desserts can sit out on a warm day, and you can even serve agar jellies warm. Gelatin, by contrast, melts around body temperature.
Agar vs gelatin
| Agar | Gelatin | |
|---|---|---|
| Source | Red seaweed | Animal collagen |
| Dissolves at | Boiling | About 50 °C / 120 °F |
| Sets at | ~32–40 °C / 90–104 °F, in minutes | Fridge temperature, over hours |
| Melts at | ~85 °C / 185 °F | ~35 °C / 95 °F |
| Texture | Firm, clean-cutting, slightly brittle | Elastic, wobbly, melts in the mouth |
| Affected by raw pineapple or kiwi | No | Yes, won't set |
That texture difference matters. Agar jellies are firmer and shorter, closer to a gummy candy's bite than to panna cotta's melt. For a softer, creamier result, use less agar.
How to use agar powder
- Whisk the powder into cold liquid so it disperses without clumping.
- Bring to a boil, stirring, and simmer for 1–2 minutes.
- Add any sugar or flavourings, then pour into moulds.
- It sets at room temperature in about 10–30 minutes; chill to firm further.
Starting ratios (powder):
- Soft set: 0.5 g per 100 ml (about 1/2 tsp per cup).
- Firm set: 1 g per 100 ml (about 1 tsp per cup).
Common issues
- Weeping. Agar gels can release liquid over time, called syneresis. Slightly more sugar or a little locust bean gum helps.
- Acid. Lemon juice or vinegar boiled with agar weakens it. Add acidic ingredients after simmering, once the mixture has cooled a little.
- Fixing a too-firm gel. Re-melt it with more liquid, boil again and re-set.
Questions
How much agar replaces gelatin?
Agar is much stronger. As a starting point, use about 1 tsp (2 g) agar powder to set 250 ml (1 cup) of liquid firmly, where you'd use roughly 7 g (one envelope) of gelatin. Use less for softer, wobbly sets.
Why didn't my agar set?
Most often it wasn't boiled long enough to dissolve. Agar must be brought to a boil and simmered for at least 1–2 minutes. Very acidic liquids can also weaken the gel.
What is the difference between agar powder, flakes and strands?
They're the same substance in different forms, but powder is the most concentrated and predictable. Roughly 1 tsp powder equals 1 tbsp flakes. Strands and bars need soaking and longer simmering.
Can I use agar with pineapple or kiwi?
Yes. Fresh pineapple, kiwi and papaya contain enzymes that break down gelatin's protein, but agar is a carbohydrate, so they don't affect it.