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Batch-type overpressure water cascading/spray retort for in-pack thermal processing


Key words pasteurisation, sterilisation, thermal processing, batch retort, water cascading, water spray, packed foods and beverages, overpressure
Latest version 2010/12/14
Completed by KU Leuven LFT

How does it work?

Primary objective An overpressure water cascading/spray retort can be used for thermal pasteurisation or sterilisation of packed foods.
Working principle A water cascading/spray retort is one of the different types of retorts that are designed to provide overpressure (i.e. the pressure supplied to a retort in excess of that exerted by the heating medium at a given process temperature) during processing which is often required to maintain the package integrity. As temperature and pressure are controlled independently, they are especially suited for packages with limited resistance to internal pressure (such as semi-rigid plastic containers, flexible pouches or trays, glass jars etc…)

The heating medium is pressurised hot water, which is cascading over a perforated top plate or sprayed by several spray bars respectively in a water cascading or a water spray retort. Cooling is achieved by cascading/spraying cold water. A water cascading/spray retort can be operated in a static or in an agitated mode. Product agitation can be realized by end-over-end rotation or by a pendular movement of the baskets holding the packaged foods (hence, not all containers undergo exactly the same degree of agitation), for example in a Steriflow retort. Agitation can also be realized through a horizontal movement of the baskets. A reciprocating actuator shakes the baskets and their contents back and forth during processing (up to 150 shakes/min in the Shaka (c) retort). The vigorous agitation causes thorough mixing of the food in the container and hence, enhances the heat penetration in the food product. In this case, all containers undergo exactly the same degree of agitation.

Additional effects The enhanced heat penetration due to product agitation permits the use of higher processing temperatures and consequently shorter process times, which on its turn results in improved product quality.

On the other hand, in agitational processes, products must be secured within the baskets while allowing the free passage of the heating medium. For this, special spacers and container retaining systems are to be used.

Important process parameters temperature, time, rotational/agitational speed
Important product parameters thermal diffusivity, geometry and dimensions, viscosity, head space

What can it be used for?

Products Food industry: packaged foods and beverages

Pharmaceutical industry: packaged products that need to be decontaminated

Operations Thermal pasteurisation or sterilisation of packaged products
Solutions for short comings Poor heat penetration rate in conventional batch type autoclaves.

What can it NOT be used for?

Products Not suited for non-packed products

For solid products, product rotation/agitation is not beneficial

Operations No information available
Other limitations damage to sensitive products like soft fruit particles that consumer like to see compact
Risks or hazards No risks/hazards


Maturity Available at lab-scale and industrial scale
Modularity /Implementation A batch-type overpressure water cascading/spray retort can easily be inserted in an existing production line
Consumer aspects No information available. No problems expected.
Legal aspects No information available, but no regulatory hurdles are anticipated.
Environmental aspects No information available

Further Information

Institutes Campden BRI, CTCPA, KU Leuven LFT
References Holdsworth, S.D. (1997). Thermal processing of packaged foods. Blackie Academic & Professional, London, pp. 283.

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Created by LiesbethV on 28 February 2012, at 14:10