How to Choose the Right Retort System for Different Packaging Types

Retort selection isn't just about hitting a sterilization temperature. Metal, glass, plastic, and flexible pouches each behave differently under heat, pressure, and water circulation — and picking the wrong system usually shows up later as deformed cans, burst pouches, or cracked jars on the production line.

Here's how packaging type generally shapes the choice.

Metal Cans

Metal cans are rigid enough to handle high temperature and pressure without much fuss, which is why they work with almost any retort type — steam retort, water spray retort, or rotary retort. Rotary retorts are worth considering specifically for viscous or particulate products (soups, sauces with solids), since the rotation keeps heat moving through the can instead of relying on conduction alone, which can cut process time by making heat transfer more even.

Flexible Pouches

Pouches have little structural strength of their own, so pressure balance is the whole game. If the air pressure inside the retort doesn't track the internal pressure of the pouch closely enough during heating and cooling, seams stretch or seals fail. Water spray and steam-air retorts are common choices here because they allow continuous overpressure adjustment — well-tuned systems can hold pressure control within roughly ±0.05 bar, which is the range needed to keep pouch seals intact through repeated heating and cooling cycles.

Plastic Containers and Trays

Plastic trays and bowls used for ready-to-eat meals are usually considered gas-containing packages, meaning there is a certain amount of headspace air or process gas inside the package.

During retort sterilization, the internal pressure of the package changes with the temperature variation inside the retort. The faster the heating or cooling rate, the more significant the pressure change will be.

The key factors affecting package deformation are not only the pressure changes themselves, but also the pressure difference between the inside and outside of the package. Differences in headspace gas volume, product viscosity, and moisture content can all affect heat transfer behavior during the sterilization process.

Therefore, the core requirement for retort systems used with plastic containers is the ability to accurately track and control overpressure. By maintaining synchronization between the retort chamber pressure and the product’s internal pressure, the pressure difference can be kept within the acceptable tolerance range of the packaging material.

This precise pressure management is the key to preventing plastic containers from deforming, swelling, or collapsing during thermal processing.

Glass Bottles and Jars

Glass doesn't fail from pressure — it fails from thermal shock. Fast temperature swings during heating or cooling are what crack jars, not the sterilization temperature itself. Water spray retorts with staged, gradual heating and cooling curves are the standard choice, since they let temperature climb and drop incrementally rather than jumping.

Beyond Packaging

Packaging type gets you to a shortlist, not a final answer. Product viscosity, fill weight, target F0 value, batch size, and how much of the loading/unloading process you want automated all factor into the final spec. Two customers packing the same product in the same container can end up with different retort configurations once these variables are added in.

Finding the Right Fit

We build retort systems and full automated sterilization lines at DTS, and packaging-and-product fit is usually the first conversation we have with a new customer — before talking about specific equipment. If you're scoping a new line or troubleshooting deformation issues on an existing one, send us your packaging and product details and we'll walk through what actually fits.