Cylinder Count Method for Determining Plate Count of Pasteurized Milk Products

Abstract

A new simplified method, the plate cyl- inder 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 cyl- inder into a petri dish with a continuous pipetting syringe. Agar was poured in the usual nmnner. For five types of milk prod- ucts obtained from retail outlets, the rep- licate variance of the loglo 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 2.8 mm long, made from a 13- gauge cannula used at a controlled dipping rate of 60 cycles per minute, delivered an average of 10.50 mg of product, with a geometric mean count of within -+- 5% of the Standard Plate Count.