Industrial thermal processing is where gellan gum either earns its reputation or loses it. The ingredient is used precisely because it can survive conditions that destroy other hydrocolloids — but only if the process is designed around how it behaves.
The three processes
| Process | Typical conditions | What it does to gellan gum |
|---|---|---|
| Pasteurisation | 72–95 °C for seconds to minutes | Well below the melting temperature of an LA gel; minimal effect |
| UHT | 135–150 °C for 2–10 seconds, then rapid cooling | Network survives; hydration and gelation timing must be managed |
| Retort / in-pack sterilisation | 115–125 °C for 10–40 minutes, then slow cooling | LA networks survive; HA gels melt and re-form |
The distinction between LA and HA is the first thing to settle. An LA gellan gel will survive retort. An HA gellan gel will melt. If your product is a retort-stable elastic gel, HA is the wrong choice regardless of texture preference.
The design problem: gelation must happen at the right moment
The central challenge in continuous processing is not thermal stability. It is that you must keep the gum fully hydrated but ungelled until the product is in the package.
Failures look like this:
- Gel in the heat exchanger. Product blocks the plates, pressure rises, production stops.
- Gel in the transfer line. Product fills partially set, giving lumps and an uneven texture.
- Gel before homogenisation. The homogeniser tears a network that has already formed, and it does not fully recover.
- No gel in the pack. Over-sequestering leaves too little free calcium, and the product is thin at end of shelf life.
How to keep the product liquid through processing
Four levers, normally used together:
1. Sequestering agents. Sodium citrate and polyphosphates bind calcium and raise the temperature window. This is the primary tool. See our article on controlling set temperature.
2. Order of addition. Add the gellan gum where the calcium is not yet present — for example, hydrate it in the water phase before the mineral or dairy ingredients are introduced. Reversing the order can cause premature gelation.
3. Hold temperature above the set point. Keep the product above the temperature at which it would gel until it is in the pack, including through any buffer tanks or holding tubes. Temperature drops in transfer lines are a common and invisible cause of partial setting.
4. Shear and timing. Product movement keeps the forming network broken up. This is protective through the line and must stop at the right point — after filling, at rest, so the network can build.
UHT specifics
Four points that matter for UHT:
- Hydration must be complete before the UHT stage. The gum needs time and temperature to hydrate. If you rely on the UHT step to hydrate it, you will get incomplete hydration and unstable suspension. Hydrate upstream, in a dedicated step.
- Very high temperatures can cause protein aggregation in protein-containing systems, particularly plant proteins. Gellan gum interacts with protein, and the aggregate structure affects both clarity and gel behaviour. Processing conditions and gellan dosage need to be developed together.
- Homogenisation timing is critical. Homogenise before the gel network forms, or accept that the structure you measure in the lab will not be the structure you get in the pack.
- Cooling rate determines texture. Rapid cooling through UHT gives a different network from slow cooling in a retort. Do not assume laboratory bench results transfer.
Retort specifics
- LA gellan gum networks are genuinely heat-stable. This is the property that makes it valuable for retort pouches, canned desserts and sterilised fruit preparations.
- Filling temperature sets the initial state. If you fill hot with an HA gel, you will fill a liquid and get a gel only after cooling. If the container geometry is awkward, the result can be uneven.
- Over-processing costs performance. Prolonged exposure to high temperature degrades the polymer over time. Gel strength that was in specification at release can decline through the shelf life if the process is at the aggressive end of the window.
- Cooling gradients matter in large containers. A large can or pouch cools from the outside in, and the gel forms progressively. Where the container is deep, the centre may cool slowly enough to give a coarser structure.
A process development checklist
- Fix the grade: LA for heat stability, HA for mouth-melt.
- Measure the calcium load of every ingredient and the process water.
- Establish the hydration step separately, with its own temperature and holding time.
- Set the sequestrant level by trial, based on set temperature measurements, not on habit.
- Map the temperature profile of the whole line, not just the process equipment — including transfer lines and holding tanks.
- Decide where homogenisation and any high-shear step sit relative to gelation.
- Test at end of shelf life, not only at release. Suspension and gel strength both drift.
What to ask a supplier
- Which grade do you recommend for a retort or UHT process, and why?
- What is your experience with sequestrant dosage in similar systems?
- Do you have data on performance after thermal processing, as opposed to in a bench preparation?
- Can you support a trial at pilot scale?
For technical support on gellan gum (E418) in thermally processed applications, see Cinogel.
Part of the E418.org gellan gum knowledge base. See also: how does gellan gum behave during scale-up from lab to production, and why does gellan gum perform differently before and after homogenization.