Biomedical subjects

V S Packard

Publications and source records attributed to V S Packard.

3 recordsLinked to original sources

PubMed1982

Quantitative estimates of beta-lactam residues in raw milk around a reference standard: collaborative study.

A collaborative study was conducted to determine the reliability of a Bacillus stearothermophilus disc assay method for differentiating various concentrations of penicillin in raw milk. Participating laboratories tested 10 different samples (including one negative) in blind duplicate. Triplicate standards were alternated with triplicate unknowns around the periphery of each of 5 different plates. Zone diameters were measured and the difference in zone size of pairs of adjacent standard and unknown samples were analyzed by a paired t-test. Penicillin concentrations 0.003 IU/mL different from the reference concentrations were consistently distinguishable at a 95% confidence level. Such discriminatory power was determined to be possible with as few as 3 plates (9 replicates) per unknown. The method has been adopted official first action.

Animals↗

PubMedDate not supplied

Enumeration of total bacteria and coliforms in milk by dry rehydratable film methods: collaborative study.

Eleven laboratories participated in a collaborative study to compare the dry rehydratable film (Petrifilm SM and Petrifilm VRB) methods, respectively, to the standard plate count (SPC) and violet red bile agar (VRBA) standard methods for estimation of total bacteria and coliform counts in raw and homogenized pasteurized milk. Each laboratory analyzed 16 samples (8 different samples in blind duplicate) for total count by both the SPC and Petrifilm SM methods. A second set of 16 samples was analyzed by the VRBA and Petrifilm VRB methods. The repeatability standard deviations (the square root of the between-replicates variance) of the SPC, Petrifilm SM, VRBA, and Petrifilm VRB methods were 0.05104, 0.0444, 0.14606, and 0.13806, respectively; the reproducibility standard deviations were 0.7197, 0.06380, 0.15326, and 0.13806, respectively. The difference between the mean log10 SPC and the mean log10 Petrifilm SM results was 0.027. For the VRBA and Petrifilm VRB methods, the mean log10 difference was 0.013. These results generally indicate the suitability of the dry rehydratable film methods as alternatives to the SPC and VRBA methods for milk samples. The methods have been adopted official first action.

Animals↗

PubMedDate not supplied

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.

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