How load configuration affects thermal uniformity in retorts

In thermal processing, precision matters. In this paper, Surdry elaborates on the influence of the loading pattern and how heating uniformity is thus affected.

Food companies often aim to maximize retort batch capacity, without considering the side effects on processing uniformity. The design of the baskets or trays and the container loading patterns are key to obtaining fast and even heating and cooling, with effect on product safety and quality.

Why Load Configuration Matters

First class retorts are expected to deliver fast and uniform thermal distribution, meaning that all containers are subjected to temperature in a narrow window of deviation. If the loading pattern does not allow proper steam and/or water flow to those containers seating away from the heating or cooling source, the deviation window will grow and longer time will be required to reach the temperature. The slower heating containers will dictate the sterilization time for the full batch, potentially causing overcook in the faster heating zones. Therefore, it is essential to choose open baskets and trays and to lay the containers in a way that heat flows with minimum resistance.

As shown in Surdry’s batch retort design, the configuration of baskets and trays plays a critical role in achieving uniform heating and cooling performance.

Key Technical Considerations:

• Pads to be inserted between layers of cans or jars must have large open area and proper thickness, while keeping stiffness for handling purposes.
• Pouches must not be overlapped to prevent heat penetration issues.
• Pouches must lay with sufficient separation to allow good steam and water circulation.
• Pouch holding trays must be designed to allow clearance between the layers for good steam and water circulation.
• Trays must be well designed to prevent pouch folding or deformation, especially in case of retorts with agitation.

Last but not least, the larger the retort the more challenging the matter. Surdry has long and wide experience in the design of all baskets, trays and layer pads for still and agitating retorts and will advise, not only on the most suitable retort size, but also on the best loading configuration to obtain consistent product quality.

Ready to optimize your thermal process?

Uniform heat distribution is key to achieving consistent product quality, production efficiency, and food safety. 

If you’re looking to improve your results or need guidance on the best loading configuration for your products, our engineering team can help.

👉 Contact our experts or explore our retort solutions to discover how Surdry can support you in achieving maximum performance.