Guidelines on the incubation testing of
ambient shelf stable heat preserved foods

Understand incubation testing - its role, methods, benefits and limitations - in the quality control of ambient shelf stable heat preserved foods.

Incubation testing involves incubating containers of heat preserved food under conditions which would stimulate the growth of micro-organisms, as one means of demonstrating the presence of viable micro-organisms in post-process heat preserved product. It is used by many manufacturers of heat preserved foods to investigate the commercial sterility of their products or identify reasons for failure. However it also has significant limitations. It does not, when used alone, provide adequate means of assuring that containers of product, manufactured during routine production, have been properly sterilised. It can also be expensive, in terms of tying up stock awaiting positive release. It should, therefore, be used with clear understanding and specific purpose.

This document, written with the close involvement of the heat preserved foods sector, was developed to provide an authoritative reference guide for all personnel concerned with incubation testing of heat preserved foods intended for ambient storage and distribution. It gives guidance on when incubation testing can be useful, illustrates why the approach adopted should be informed by the purpose of the test, provides advice on the practical aspects of conducting such tests, and details their limitations. It also provides useful background information on sampling and a glossary of relevant terms.

Contents

Introduction

• Objective and scope
• Limitations of incubation testing

Sampling plans

Applications of incubation testing

• Identification of under-processing or leaker spoilage in routine manufacture
• Incubation testing in case of observed deviation to thermal process
• Incubation testing in case of increased susceptibility to leaker spoilage due to suspect deficient closures and/or microbial quality of cooling water
• Large scale incubation testing for routine surveillance of rate of container failure
• Incubation testing relating to new or modified products, containers or manufacturing plant
• Transit testing

Practical considerations for incubation testing

• Temperatures and times for incubation testing
• Post incubation examination of containers
• Incubation facilities
• Point of sampling
• Container examination
• Personnel

Laboratory incubation investigation in the case of observed spoilage of heat preserved foods

Glossary

References

Appendix 1 - Routine measures for quality assurance of safety of heat preserved foods

Appendix 2 - Model situations in which incubation testing may be used