Uses and Limits of MicrobialTesting

摘要

Microbiological testing is an integral part of most microbiological food safety problems, making up a significant amount of the effort of many food microbiologists. Effective use of these analytical tools requires both a thorough understanding of the technical details of methods being employed and how the performance of the methods is influenced by smpling limitations. However, too often thelatter is incompletely evaluated or understood. In particular, improvements in the sensitivity and specificity of new methods can be effectively lost if it is accompanied by a decrease in sample size. The basis for sampling requirements, particularly when a microorganism of concern is present at low levels, is based on the probability of detecting the specific portion of food being tested from a larger population of food portions.Two general approaches based on statistical requirements are most often employed in the testing of food samples, "within- batch testing" and "between-batch testing." The puipose of with-in batch testing is to establish that a specific lot of food is "safe" in regard to a specific hazard at a specified level of confidence. This approach assumes no prior knowledge of the history of the food. Practical sampling considerations generally limits its effectiveness to batches where more than 1% of the samples are ontaminated. Often referred to as process control testing, the purpose of between-batch testing is verification that a process is operating as intended. This type of testing assumes that there is extensive knowledge of the system being evaluated. This approach can be very sensitive to changes above an established baseline, however, that sensitivity is again dependent on the number of samples taken and the inherent number of contaminated portions produced by the system. An understanding of which tool to employ and the limitations of those tools are critical to the effective use of microbiological testing.