Incubation test may be carried out in the laboratory or with bulk samples. With the former, the validity of the results must; be verified before any conclusions as to the suitability of the test sample (and by implication, the suitability of the population from which the samples were drawn). Factors to be considered when selecting testing procedures for laboratory incubation include:
*the purpose of the test and its statistical basis;
*the validity of the selection of incubation temperatures;
*the method of examination of incubated containers (e.g., not all spoilage will cause blown cans); *the sample size required to draw statistically significant conclusions; and
*the tolerable levels for accepting lots with given levels of defectives.
With bulk incubation the factors to be considered include:
*the method can only provide the incidence of blown cans in the lot, under examination;
*the method can highlight changes in spoilage levels, and prompt management to find the causes of any trends; and
*because of the heating lags in bringing cooled cans to incubation temperatures, it is advantageous to commence incubation as soon as possible after the cans leave the retort, when they will still retain some of the heat from the process.