number exceeding 10 per g from three or more of the five sample units examined (n=5, c=2, m=10, M=103). Salmonella organisms should not be recovered from any of ten sample units examined when the test is carried out according to the method described; (n=10, c=0 m M=0).
METHODS OF MICROBIOLOGICAL ANALYSIS OF FOOD AND WATER 1. ENUMERATION OF MESOPHILIC AEROBIC BACRERIA (Aerobic plate count) Principle
This method is based on the assumption that the microbial cells present in a sample mixed with an agar medium each form visible, separated colonies. This is obtained by mixing decimal dilutions of the food sample homogenatte or warer with the medium After incubation of the plates at 35 OC 72 hours the number of mesophilic aerobic bacteria per g of food sample is calculated from the number of colonies Obtained in selected petridishes at levels of dilutions giving a significant result. it should be borne in mind that this method, as all other has some limitations
Microbial cells often occur as clumps, clusters, chains, or pairs in foods, and may not be well distributed irrespective of the mixing and dilution of the sample. Consequently, each colony that appears of the agar plate may
arise from a single cell or from groups of cell