PROCESS Modes
Rotation and Oscillation
Simulation of End-Over-End Rotation Full rotation of 360º.
Batch retorts can be operated using different processing media and in different modes. The mode used will depend on the kind of product being processed. Static retorts are used for solid products or products in viscous sauces which heat mainly by conduction. Any agitation for these products would result in very little heat transfer benefit. Delicate products that could get damaged by agitation should also be processed in the static mode. Products that heat by convection would greatly benefit from some agitation during processing. This would increase the rate of heat penetration into the product, and reduce the processing time; thereby reducing the total energy consumption of the process, and improving the product quality.
There are two types of agitation: end-over-end rotation and oscillation.
End-Over-End Rotation
1
FULL ROTATION
End-over-end rotation uses the headspace bubble to aid mixing, as the packs are rotated 360°. The full rotation does not suit all packaging types.
OSCILLATING
STATIC
Static retorts are typically used where agitation is either not necessary, or may damage the product or packaging. Product heating occurs by conduction and/or by natural convection.
Gentle rocking induces mixing inside the packaging where end- over-end rotation may not be suitable. Products in flat-lying containers such as pouches and trays will especially benefit from the increased heat transfer rate induced by gentle agitation.
Rotary operation of a batch retort results in forced convection which speeds up the heat transfer to the cold spot of the package, even in products with high viscosity. Shorter processing times result in better quality and retain more of the nutritional value. Furthermore, the mixing of the product prevents clumping and product burn-on inside the packaging.
Oscillation
2
For flexible pouches - and semi-rigid cups and trays - the gentle rocking movement of oscillation is the preferred option.
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