title: A proficiency test system to improve performance of milk analysis methods and produce reference values for component calibration samples for infrared milk analysis.
abstract: Our goal was to determine the feasibility of combining proficiency testing, analytical method quality-assurance system, and production of reference samples for calibration of infrared milk analyzers to achieve a more efficient use of resources and reduce costs while maximizing analytical accuracy within and among milk payment-testing laboratories. To achieve this, we developed and demonstrated a multilaboratory combined proficiency testing and analytical method quality-assurance system as an approach to evaluate and improve the analytical performance of methods. A set of modified milks was developed and optimized to serve multiple purposes (i.e., proficiency testing, quality-assurance and method improvement, and to provide reference materials for calibration of secondary testing methods). Over a period of years, the approach has enabled the group of laboratories to document improved analytical performance (i.e., reduced within- and between-laboratory variation) of chemical reference methods used as the primary reference for calibration of high-speed electronic milk-testing equipment. An annual meeting of the laboratory technicians allows for review of results and discussion of each method and provides a forum for communication of experience and techniques that are of value to new analysts in the group. The monthly proficiency testing sample exchanges have the added benefit of producing all-laboratory mean reference values for a set of 14 milks that can be used for calibration, evaluation, and troubleshooting of calibration adjustment issues on infrared milk analyzers.
authors.affiliation: Department of Food Science, Cornell University, Northeast Dairy Foods Research Center, Ithaca, NY 14853.
authors.forename: Karen L
authors.initials: KL
authors.lastname: Wojciechowski
authors.affiliation: Department of Food Science, Cornell University, Northeast Dairy Foods Research Center, Ithaca, NY 14853.
authors.forename: Caterina
authors.initials: C
authors.lastname: Melilli
authors.affiliation: Department of Food Science, Cornell University, Northeast Dairy Foods Research Center, Ithaca, NY 14853. Electronic address: dmb37@cornell.edu.
authors.forename: David M
authors.initials: DM
authors.lastname: Barbano
mesh_terms: D000818:Animals; D002138:Calibration; D007753:Laboratories / Q000592:standards*; D008892:Milk / Q000737:chemistry*; D011786:Quality Control; D012016:Reference Values; D015203:Reproducibility of Results
keywords: Kjeldahl; ether extraction; proficiency testing