Precision pasteurization with tunnels and Dynamic PU Control
In the food and beverage industry, achieving consistent pasteurization is critical, not only for product safety but also for maintaining quality and optimising production efficiency. For over three decades, Molenaar has been designing and manufacturing in-container pasteurization tunnels for a diverse range of products, from pickles in glass jars to tomatoes in steel cans and beverages in aluminium cans. This depth of experience, combined with advanced engineering innovation, positions the company as a trusted partner for food and beverage processors worldwide.
Understanding pasteurization units (PUs)
A Pasteurization Unit (PU) is a measure of the heat applied to a product over time, relative to a reference temperature specific to that product. Different products – depending on their composition, pH and manufacturing process – require different reference temperatures. The correct PU is vital: too little heat can compromise food safety; while too much can negatively affect flavour, colour, aroma or texture.
In beverage processing especially, certain products like beer and cider, are sensitive to over-pasteurization, making precise PU control essential. Excess heat also increases energy consumption, which is an important consideration in today’s sustainability-conscious manufacturing environments.
How tunnels work
Pasteurization tunnels operate by gradually heating products to the required temperature, holding them for the necessary duration and then cooling them back down. In most cases, this involves taking a product, moving it through sequential heating zones until it reaches the “hot zone” for pasteurization, and then progressively cooling it.
To improve energy efficiency, Molenaar integrates energy regeneration systems into its tunnel designs. These systems capture heat from the outgoing, pasteurized product and transfer it to the incoming cold product, reducing the heating and cooling demand. This closed-loop approach not only conserves energy but also minimises water usage – water is continuously recirculated within the tunnel rather than wasted.
Dynamic PU Control: Responding to real-world production challenges
In a perfect production environment, a line would run continuously with no stoppages. In reality, downstream issues, maintenance needs, or product changeovers can cause interruptions. Without proper control, products held stationary in the tunnel during a stoppage can receive excessive heat, leading to over-pasteurization and compromised quality.
Dynamic PU Control addresses this challenge by automatically adjusting the temperature in individual tunnel zones during stoppages. Even if products are not moving, the system can dynamically “move” the heating and cooling zones within the tunnel to maintain the target PU without exceeding it. Once production restarts, the system adjusts temperatures in real time to bring products back into the correct pasteurization profile.
The result:
- Increased line efficiency
- Improved quality and consistency
- Reduced rework and waste
While dynamic PU control is particularly valuable in beverage production, where product sensitivity is high, certain beverage applications can benefit as well, especially for items that are carbonated or where precise quality control is very important.
PU Limiting for less sensitive products
For products less sensitive to heat, such as certain fruit juices, a simpler form of control known as PU limiting can be applied. This offers many of the benefits of dynamic PU control but at a lower cost and with reduced system complexity.
Features that set Molenaar apart
Molenaar’s tunnel pasteurizers are designed for performance, reliability and ease of maintenance. One of their standout design choices is the use of cascade shower trays, which are also referred to as “shower pans” instead of conventional spray bars. These trays maintain a consistent depth of water and deliver a defined flow pattern over products, ensuring uniform heat transfer. Unlike spray systems, which can suffer from blocked nozzles or misdirected sprays, cascade trays are easy to inspect and clean, reducing the risk of unnoticed process issues.
Key advantages of this approach include:
- High-volume water flow for better heat transfer
- Closed-loop water system to minimise consumption
- Easy inspection and maintenance via accessible tray design
- More predictable thermal performance for consistent pasteurization outcomes
Additionally, Molenaar manufactures its own shell-and-tube heat exchangers, ensuring long-term reliability and allowing for customisation to specific client requirements.
A long-term view on pasteurization
Investing in advanced tunnel pasteurization systems with dynamic PU control is not just about meeting today’s production goals; it’s about future-proofing operations. From reducing waste and maintaining product quality to ensuring energy and water efficiency, Molenaar’s solutions deliver measurable benefits over the long term.
With over 30 years of expertise, a commitment to precision engineering and a deep understanding of both food and beverage processing needs, Molenaar continues to lead the way in tunnel pasteurization technology.
