New two-stage sampling inspection plans for bacterial cell counts

Microbiological testing represents a significant expenditure for producers. Two new double sampling plans employing a compressed limit in the first stage of inspection were proposed to reduce the testing costs. These plans were designed for sanitary characteristics where the bacterial count generally fits a Poisson or a mixed-Poisson distribution. Both plans showed improved consumer protection with substantially smaller average sample size. The application of the new plans was validated using an empirical dataset of aerobic plate counts observed in milk powder samples. The new plans enabled a sample size reduction of between 20 and 75% compared to the actual sampling procedures.