Microbiological collaborative studies for quality control in food laboratories: reference material and evaluation of analyst's errors.
Working groups of the Federal Health Office in Germany and of the International Dairy Federation (IDF) have developed a quality assurance system to assess the analyst performance for colony count methods. The experiment design consists of several dilution series produced from a homogeneous sample suspension. Each series contains a number of twofold dilution steps with parallel plates on each level. The structure of this design permits a detailed analysis of the total variance and identification of analysts' methodological errors as single effects. A computer-based interpretation aid may classify the laboratory as working in correspondence with good laboratory practice ('acceptable') or, otherwise, furnishing 'to good' or 'unacceptable' results. Some examples are given for deviation depending on individual faults. Both, internal quality assurance and collaborative studies demand suitable reference samples. The reference material used has to meet certain requirements concerning homogeneity, contamination level and microbiological stability during a period of storage and transport. A naturally contaminated sample material was prepared, which has been used successfully in microbiological collaborative studies.
Berg
C
C
Institut für Lebensmittelhygiene, Veterinärmedizin der Freien Universität Berlin, Germany.
Dahms
S
S
Hildebrandt
G
G
Klaschka
S
S
Weiss
H
H
D000818:Animals; D001431:Bacteriological Techniques; D002417:Cattle; D015169:Colony Count, Microbial; D003627:Data Interpretation, Statistical; D005516:Food Microbiology / Q000592:standards*; D006801:Humans; D008460:Meat / Q000382:microbiology; D011786:Quality Control; D012015:Reference Standards; D012985:Software Design; D013552:Swine