Keywords
reference material
food microbiology
How to Cite
Abstract
Proficiency tests are considered relevant tools of quality control programs used to monitor the laboratory performance and to assess the reliability of tests results. In Brazil, the provision of proficiency testing (PT) is restricted to food microbiology area. Furthermore, high costs reduce the regular participation of national laboratories in these tests. This study evaluated the freeze-drying technique employed for preparing reference materials (RM) to be used in the PT schemes for detecting Salmonella spp. in milk. The concentration of inoculums used for preparing two batches of RM was determined, and the procedures for matrix contamination were standardized. The control trials were established in order to monitor the quality of the produced RM, and among them, there are long and short-term homogeneity and stability assays. The freeze-drying technique proved to be a suitable procedure for producing RM for PT. The RM were stable for the first three months when stored at -20ºC, nevertheless, viability loss could be observed after 12-month storage. The RM were stable at 4°C at short-term stability, although when the products were kept at 25°C and 37°C for seven days, a significant reduction in the number of cells could be observed.References
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