A Collaborative Study to Determine the Feasibility of Using 0.40-, 0.20-, 0.14-, and 0.10-Inch-Diameter Discs to Measure Sediment in Fluid Milk.

This collaborative study was done to determine whether laboratory personnel could successfully grade raw milk for sediment content using 0.40-, 0.20-, 0.14-, and 0.10-inch-diameter sediment discs. The 0.40-inch disc presently is accepted for grading sediment in mixed bulk milk samples. Technicians in 17 separate laboratories made 1,360 determinations (80 per laboratory) or 20 determinations for each size of sediment disc. Each laboratory graded the same set of samples. Samples were graded using photoprint standards that were prepared for this study. The laboratories were evaluated on the ability of laboratory technicians to grade the various sizes of sediment discs. Technicians in 13 of the 17 laboratories graded samples showing no significant differences in their ability to grade the various sized sediment discs. Four laboratories were not consistent in their ability to grade discs and showed significant differences in agreements with the previously determined sediment level as the diameter of the disc was reduced. Based on these results, most laboratories evaluated were capable of grading sediment discs with diameters of 0.40-, 0.20-, and 0.14-inch with consistency. With properly trained personnel in the laboratories, the study indicates the 0.10-inch diameter disc also can be used effectively for grading sediment in milk.