A Comparison Of Deft Clump Counts Obtained In 8 Dairy Laboratories Receiving Replicate Samples Of Preserved Raw-Milk

In an interlaboratory trial, the Direct Epifluorescent Filter Technique (DEFT) for estimating the hygienic quality of raw milk was compared with the colony count method. The results, from replicate samples of 60 chemically preserved milks examined at eight dairy laboratories, showed linear correlation coefficients ranging from + 0.19 to + 0.90. DEFT results depended on the skill of the operator and agreed less well with colony counts made before preservation than with colony counts made at the same time as DEFT counts. The combined DEFT counts from all laboratories compared with colony counts made after preservation showed a linear correlation coefficient of + 0.87; the equation for the regression line was y = 1.00x + 0.04, indicating that the DEFT can provide results comparable to those of the colony count.