FIELD OF THE INVENTION

Agricultural and Biological Engineering – Continuous Aseptic Processing

BACKGROUND

Aseptic processing/packaging of low-acid foods with large particles (e.g. chunky soup) has been thwarted in the United States by concerns about residence time distributions of particles in holding tubes. Prediction and/or control of residence time is needed to assure the correct processing time for each component of the stream flow (e.g. liquid, small particles and large particles). A wide distribution of residence times means that some components are processed for much shorter times while other components are processed for much longer times than average. To compensate, often the processing time is increased to insure that the fastest moving components in the flow stream receive the minimum processing time. Then the slowest moving components in the flow stream are over-processed (e.g. over-cooked). Over-processing may lead to inferior quality product, increased energy usage and/or reduced throughput.

Several approaches have been used to resolve the problems associated with a wide distribution of residence times in continuous processing. One approach is to use empirical data or mathematical models to predict residence time distributions for a particular set of flow conditions. The second approach is to control flow parameters such as laminar or turbulent flow, tube diameter, tube length or flow path to create the desired residence time distributions. A third approach is to use batch processing rather than continuous processing. However, none of these approaches provides a completely satisfactory solution to the problem.

INVENTION DESCRIPTION

This invention controls the residence time of all components of the flow stream thereby reducing or eliminating the difference between the fastest and slowest moving components. The result is that all components receive the same processing time. More uniform residence time eliminates over-processing and under-processing.

ADVANTAGES

· Enables aseptic processing of low-acid foods with large particulates

· Better quality food product

· Aseptic processing results in reduced cost of packaging

· More attractive packaging can be used

OTHER APPLICATIONS

Although this discussion has focused on aseptic food processing, the same principles for the control of residence times apply for reactors, heat exchangers and holding tubes in a wide variety of other applications.