Automated technique for sampling milk from farm bulk tanks: collaborative study

An automated, in-line, mechanical technique for sampling milk from farm bulk tanks was evaluated in a collaborative study. The automated sampling device, which is mounted on the milk intake line, contains an electronically controlled peristaltic pump. The device takes a representative sample of the entire volume pumped through the system. Samples taken can be analyzed for both composition and microbiological quality. The study was performed in 3 phases. In the first 2 phases, samples taken by manual and automated methods were compared in analyses for somatic cell count, antibiotics, fat, protein, lactose, and solids-not-fat. The third phase, using a modified procedure, was designed to compare sampling methods in analyses for total bacteria count (standard plate count), psychrotrophic bacteria count, and coliform count. Evaluation of the data by a nested ANOVA indicated no difference between results for samples taken by the automated and manual methods (P = 0.05) in Phases 1 and 2, irrespective of whether the bulk milk was agitated before sampling. By introducing a sanitizing step between farms in Phase 3, the automated method also provided samples comparable with those taken manually for microbial analyses. The automated method has been adopted first action by AOAC International.