Gellan gum's thermal behaviour is the reason it can do jobs no other hydrocolloid can — and the reason products sometimes fail in ways that look mysterious. This is a reference guide to set and melt temperatures, and how to use them.
The two numbers that define every gel
Every gellan gum gel has:
- a setting temperature — the temperature at which it forms a gel as it cools
- a melting temperature — the temperature at which it liquefies again as it is heated
The gap between them is called thermal hysteresis. Gellan gum is unusual in that the gap is not the same for the two grades.
| Low acyl (LA) | High acyl (HA) | |
|---|---|---|
| Setting temperature | Lower | Higher |
| Melting temperature | Much higher | Close to the setting temperature |
| Hysteresis | Large | Small |
| Practical meaning | Heat-stable gel; survives processing | Thermally reversible; re-melts readily |
| Mouth behaviour | Does not melt in the mouth | Melts in the mouth |
That single difference in hysteresis explains most of the application choices between the two grades.
Orientation table
These values are for orientation only. Set and melt temperatures shift substantially with ion type and concentration, polymer concentration, total soluble solids, pH and the presence of other hydrocolloids or proteins. Establish your own curve for your own formulation — do not design a process around a table from an article.
| Parameter | Low acyl (LA) | High acyl (HA) |
|---|---|---|
| Hydration temperature (practical target) | Above about 85 °C | Above about 80 °C |
| Setting temperature on cooling | Roughly 30–50 °C, higher with more calcium | Roughly 55–70 °C |
| Melting temperature on reheating | Roughly 85–105 °C | Roughly 65–80 °C |
| Behaviour on retort | Network survives | Gel melts and re-forms on cooling |
| Behaviour in hot fill | Can fill hot, sets in pack | Sets only on cooling in pack |
What moves the numbers
| Variable | Effect |
|---|---|
| More calcium or magnesium | Raises the setting temperature (gel forms earlier on cooling) |
| More potassium or sodium | Effect in the same direction, needing higher concentration |
| Higher polymer concentration | Slightly raises both temperatures |
| Higher total soluble solids | Generally raises the setting temperature |
| Lower pH | Interferes with hydration and network formation; can raise the effective set temperature and weaken the gel |
| Sequestering agents | Lower the setting temperature by removing free calcium |
| Shear during cooling | Delays gel formation; high shear can prevent a firm gel forming at all |
| Other hydrocolloids | Modify both temperatures; galactomannans in particular change the network |
Using the numbers in process design
If you need a heat-stable gel — a fruit piece in a retort pouch, a gelled dessert that survives sterilisation — LA gellan gum's large hysteresis is exactly what you want. The gel melts well above any processing temperature you will apply.
If you need a melt-in-the-mouth gel — a dessert that feels soft rather than rubbery, a soft confection — HA gellan gum's small hysteresis and low melting temperature are the point. The gel softens at body temperature and releases flavour.
If you need to fill hot and set in the pack — this is the classic use of LA gellan gum with a sequestering agent. Keep the calcium unavailable and the product above the setting temperature through filling, then let it set as it cools in the container. See our article on controlling set temperature for the technique.
If you need to know why a gel is not forming — check the calcium level and the temperature reached. A gel that never hydrates properly cannot set, no matter how much calcium you add.
Three cautions
1. Hysteresis means you cannot use the setting temperature as a proxy for the melting temperature. A gel that set at 40 °C may not melt until over 90 °C. Formulators used to gelatin, where the two are close, find this surprising.
2. Cooling rate changes the result. Slow cooling gives the network more time to organise and generally gives a stronger, more uniform gel. Fast cooling can leave you with a weaker or uneven structure. A recipe that works in a beaker on a bench may behave differently in a cooling tunnel.
3. Shear during cooling changes the result more than temperature does. In a suspension beverage, the weak gel network is deliberately disrupted by pumping and then reforms at rest. That is a feature — it is how a pourable drink can still hold pulp. In a firm gel application, the same shear would prevent gelation. The distinction between a fluid gel and a set gel is largely a shear-and-timing question, not a formulation one.
The test to run on your own system
Build a simple curve for each new formulation:
- Prepare the mix with everything except the gellan gum.
- Hydrate the gellan gum fully at a known temperature.
- Cool slowly, at a controlled rate, while measuring viscosity or observing gel formation. Record the temperature at which the structure forms.
- Reheat slowly and record the temperature at which it liquefies.
- Repeat at two different calcium levels and two different total solids levels.
That is half a day of laboratory work, and it removes most of the guesswork from the rest of the project.
For grade recommendations and technical data on gellan gum (E418), contact Cinogel.
Part of the E418.org gellan gum knowledge base. See also: why does gellan gum need to be heated before it works, and a gellan gum formula for a heat-reversible gel.