Cylinder Count Method for Determining Plate Count of Pasteurized Milk Products

A new simplified method, the plate cylinder count, was developed for pasteurized milk and milk products, and the precision of this technique was compared with that of the plate loop and standard plate counts. A cylinder made from a cannula was used to obtain a 0.01-ml sample of milk or milk product. Milk was washed from the cylinder into a petri dish with a continuous pipetting syringe. Agar was poured in the usual manner. For five types of milk products obtained from retail outlets, the replicate variance of the log10 counts was essentially the same for the plate cylinder and standard plate counts (0.00308 and 0.00288). The plate loop technique was less precise and had a variance of 0.00488. A cylinder 2.8mm long, made from a 13-gauge cannula used at a controlled dipping rate of 60 cycles per minute, delivered an average of 10.50mg of product, with a geometric mean count of within±5% of the Standard Plate Count.