Sampling food for microbial testing is a risk management strategy used
to evaluate whether a food safety system is correctly implemented. Within-batch
testing can be accomplished to comply with microbiological criteria or to assess
whether the food production process is under control. Generally, sampling plans can
be designed to meet the consumer’s and/or producer’s quality requirements, and
have been conventionally derived by borrowing notions of acceptance sampling
theory from classical quality statistics. This chapter describes and illustrates the
methodologies to derive the different types of sampling plans used for microbiological
criteria in foods; namely, the two-class attributes sampling plans (based on
prevalence, on concentrations, and with an enrichment step) and the variables sampling
plans. The chapter also discusses the weakness of the classical assumption
that the measure of the quality characteristic (i.e., log microbial concentration) is
normally distributed among food units with a variance that is approximately stable
batch to batch; and provides an insight to novel modelling trends to produce more
efficient and discriminatory sampling plans.
