Thermal Processing

Over the past 25 years, H.G. Molenaar has established itself as the indisputable leader in the field of in-container food and beverage thermal processing systems. Our leading products include Continuous Rotary Sterilizers and Tunnel Pasteurizers.

Process Laboratory

Our new Thermal Process Laboratory allows customers to perform in-container heat penetration studies using both Rotary and Static Simulators, coupled with the latest measuring instruments and thermal process simulation software.

The laboratory is equipped with a large diameter Rotary Simulator that can emulate continuous rotary cooking processes in machines up to 2,600 mm in diameter. This simulator can also perform static and orbital agitation processes in a steam or full immersion environment.

A Tunnel Pasteurizer simulator is also available to perform heat penetration tests for products such as beer, fruit juice or other high-acid food packaged products. Accelerated shelf life trials can be conducted in our incubator.

Customers from around the world have used our invaluable pilot facility in order to establish key processes. And by working closely with our clients, we are able to tailor designs to suit the customer’s exact requirements.

Continuous Rotary Sterilizers

Today more than 50% of the world’s canned foods are processed in Continuous Rotary Cookers and Coolers.

• Better final product quality
• Better final product consistency
• Reduced processing times
• Reduced processing risk
• More energy efficient
• Lower water consumption
• Very low labour requirements
• Very low maintenance requirements.

Operating Principle

Once cans have been filled and closed, they are conveyed and presented to the infeed device of the cooking shell. The infeed device serves to synchronize cans and transfer them into the rotary infeed valve of the cooker. The cooking vessel is pressurized by means of direct steam injection to the desired cook pressure and temperature.

From the infeed valve, cans are then transferred into a slotted rotating reel. A static spiral mounted on the inside of the shell guides cans along the length and through the slots of rotating reel. Once the cans have progressed to the end of the reel, they are ejected into a transfer valve. From here they can either be transferred into another cooking vessel or into a cooler-pressure or atmospheric. Pressure coolers are pressurized with over-pressure air and are filled with cooling water to effect cooling of the product. A discharge valve mounted at the end of the cooler delivers cans to the factory’s downstream conveyors.

The Process Advantage - Improved Heat Penetration

Continuous Rotary Cooker and cooler systems provide a very effective means of agitating the product during processing. This agitation generally makes it possible to decrease processing times and to process at higher temperatures.

During each reel rotation, cans under-go three agitation phases: orbital, transition/sliding and rolling agitation. The agitation serves to facilitate convective heat transfer through the product and thus heat penetration is increased.

Since the product is always moving inside the can, it is possible to cook at even higher temperatures and shorter times, thereby further enhancing product quality. The results speak for themselves: improved, consistent product quality.

3-phase agitation for each reel revolution

Large Capacity Shells

Large Capacity Shells are what we call the “Molenaar advantage”. As early as the 1970s, H.G. Molenaar recognized the need for higher speed sterilizers in response to market demands for increased speeds, lower maintenance requirements and systems that occupy less factory floor space. As such, we pioneered large diameter, Large Capacity Shells with the introduction of our first machine in 1978 to a local client.  

Larger holding capacities mean:

• Higher speeds
• Fewer shells
• Fewer valves
• Less moving parts
• Less floor space
• Less maintenance
• Lower energy consumption
• Lower operating costs.

The market responded positively - and fast. Fewer than two years later, we started exporting our technology to Europe.

Our pioneering efforts also saw H.G. Molenaar build the Largest Rotary Sterilizer System in the world. In the late 1980s we delivered to a European customer a massive twin system that processed more than 50 tons of product per hour.

With an ongoing focus on research and development, we have refined the basic design of our sterilizers and have introduced features that provide tremendous value to customers. Innovations include:

• Soft star infeed systems
• Low-lube stainless steel valves
• Tapered “T” spirals
• Rotor design to allow free internal access
• Improved “cleanability”
• Clutch-outs
• Electronic braking
• Debris-friendly condensate removal systems
• State-of-the-art, accurate, user-friendly recipe-driven control systems.

H.G. Molenaar continues to enjoy an ever-increasing share of the sterilizer market.

Retorts for batch sterilization

H.G. Molenaar has three different models of retorts namely static (steam/air), full water immersion with cage rotation and super heated water spray. The static retorts are manufactured in either vertical or horizontal configuration. Carbon steel or stainless steel construction is possible. Trolleys are used to load the baskets into horizontal retorts. Gantry systems are usually employed for loading baskets in vertical retorts.

Pasteurizers

With more than 50 years worth of thermal process experience, H.G. Molenaar has become a leader in the design and manufacture of Tunnel Pasteurizers. Our multi-zone design features a regenerative recirculation system where heating and cooling zones interact - resulting in substantial energy savings.

Typical applications are the in-container pasteurization of bottled juices, beer, high-acid canned products, pickled vegetables and more. Suitable containers include glass or PET bottles, cans or pouches.

Machine Design

Product is transported through the pasteurizing tunnel by an Intralox modular conveyor belt. The tunnel is divided into several heating and cooling zones, each with a separate sump, re-circulating pump and cascade shower trays. As the product passes through the tunnel, it travels underneath the shower trays and is subjected to a particular zone shower temperature. In this way, it is first heated (pasteurized) and later cooled.

The heating medium (steam) is separated from the pasteurizing water by a plate heat exchanger. Cooling water can also be separated if required.

Energy Considerations

By employing regenerative zones in our design, energy consumption is effectively minimized. Typical regenerative energy consumption of a Molenaar pasteurizer is as follows:

Pasteurizer Simulator

Our Pasteurizer Simulator is an exact small-scale replica of our pasteurizers. Products
can be tested in our simulator to develop thermal processes. With a given temperature
profile, the accumulated pasteurizing units (PU) can be calculated and the process
verified or thereafter refined. Once the desired process is determined, it can be
incorporated into the design of the commercial production machine.