Microbiological Analysis of Food and Water

285 Pages·1998·20.72 MB·English

by  N.F. Lightfoot

Microbiological Analysis of
Food and Water:
Guidelines for Quality Assurance
This Page Intentionally Left Blank
Microbiological Analysis of
Food and Water:
Guidelines for Quality Assurance
Edited by
N.F. Lightfoot
Public Health Laboratory Service
Newcastle upon Tyne
U.K.
E.A. Maier
European Commission
DG XII Measurement and Testing Programme
Brussels
Belgium
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First edition (hardbound) 1998; Second impression 1999; Third impression 2003
Paperback edition 1999; Second impression 2003
Library of Congress Cataloging-in-Publication Data
Microbiological analysis of food and water : guidelines for quality
Assurance / edited by N.F. Lightfoot, E. A Maier.
p. cm.
Includes bibliographical references and index.
ISBN 0-444-82911-3 (hardcover : alk. Paper) ~ ISBN 0-444-50203-3 (pbk. : alk. Paper)
I. Food-Microbiology. 2. Water-Microbiology. 3. Food industry
and trade-Quality control. 4. Water quality. 1. Lightfoot, N. F. O^igel F.), 1945-
II. Maier, E. A.
QR115.M46 1998
664'.00r579-dc21 98-13035
CIP
ISBN: 0-444-82911-3 (hardcover)
ISBN: 0-444-50203-3 (paperback)
@ The paper used in this publication meets the requirements of ANSI/NISO Z39.48-1992 (Permanence
of Paper).
Printed in The Netherlands.
Preface
In 1986, the European Commission began to support research and
development activities in the field of microbiological measurements.
Within the BCR (Community Bureau of Reference), and later within
the Measurement and Testing Programme (M & T Programme), sev
eral projects were launched which covered various aspects of food
and water microbiology.
The main objectives of these projects were to develop adequate
tools for the validation of microbiological measurement and testing
methods. Two projects — food and water microbiology — included
the development of representative and stable reference materials,
and involved more than one hundred laboratories from the European
Union in interlaboratory studies. Fundamental research on the
behaviour of microbes in spray-dried milk powder was undertaken.
Measurement methods and statistical treatment tools were devel
oped to assess the homogeneity and stability of these reference mate
rials, and the results led to the development of several reference
materials used in European-wide interlaboratory studies. Several
bacterial strains were studied in food (salmonella, listeria, B. cereus,
S. aureus, C. perfringens, E. coli) and water (E. faecium, E. cloacae,
E. coli, salmonella and C. perfringens). For each of the studied
microbes, several methods of measurement or testing were com
pared. Quality assurance (QA) and quality control (QC) items have
been developed. The major achievements of these projects were:
(i) the production and validation of several standard operating
procedures for basic components of microbiological testing or
measurement methods (e.g., measurement of pH of culture
media, measurement of temperature in incubators, etc):
vi Preface
(ii) the development and validation of working tools for the proper
organization of interlaboratory studies (transport of samples,
analj^ical protocols, etc) and statistical treatment of the results;
(iii) the production and certification of six reference materials.
In addition to these two projects, the Commission has also sup
ported a study on the determination of faecal contamination of sea-
water. As the stability of microbes and the sea-water matrix could
not be guaranteed in a large-scale interlaboratory study (instability
during transport), the evaluation of the methods was organized in
one central laboratory where the participants applied their own
methods to common sea-water samples.
Finally, research projects on the development and validation of
new, rapid microbiological measurement methods were also sup
ported by the Measurement and Testing Programme.
Within these projects, discussions revealed the necessity of devel
oping several important procedures for proper quality assurance and
quality control systems in microbiological laboratories. Many of
these missing procedures were already known in other fields of meas
urement sciences, but had not been used in microbiology. Some QA
and QC principles and tools were already known, but were not read
ily available to all microbiologists. Finally, the knowledge developed
in the projects by the participating laboratories needed to be made
available to all testing laboratories through the development of a
complete set of guidelines. The importance of these guidelines was
reinforced by the implementation of national accreditation systems
and their mutual recognition within the European Union following
the resolution (90/Cl/Ol of 21 December 1989) of the European
Council on the 'global approach to conformity assessment'. The
accreditation systems are based on European Standard EN 45001,
which lists several requirements to be fulfilled by laboratories. Sev
eral procedures (e.g., statistical control, use of reference materials,
validation of methods, proficiency testing, etc.) are still not used by
microbiologists, and need to be translated into microbiological terms
or adapted to the particular situation of microbiological measure
ments or testing.
Some participants in previous BCR projects recognized the impor
tance of the task. With the help of other leading QA and QC
Preface vii
microbiology specialists in Europe, they decided to prepare a com
plete set of guidelines on how to start and implement a quality sys
tem in a microbiological laboratory. This project has been supported
by the Commission through the Measurement and Testing
Programme.
The working group included food and water microbiologists from
various testing laboratories, universities and industry, as well as
statisticians and QA and QC specialists in chemistry.
This book represents the outcome of their work. It has been writ
ten with the express objective of using simple but accurate wording,
to be accessible to all microbiology laboratory staff. To facilitate read
ing, the more specialized items, in particular some statistical treat
ments, have been added as an annex to the book. All QA and QC tools
mentioned within these guidelines have been developed and applied
by the authors in their own laboratories. All aspects dealing with ref
erence materials and interlaboratory studies have been taken in a
large part from the projects conducted within the BCR and M & T
programmes of the European Commission.
The European Commission and the editors wish to express their
sincere thanks to the authors of these guidelines for their tremen
dous effort. Thanks are also due to the participants and organizers of
the former microbiology projects of the Commission, who produced
the basic information and materials on which several aspects and
conclusions of these guidelines are based.
It is appreciated that with so many different quality control proce
dures, their introduction in a laboratory would appear to be a formi
dable task. The authors recognize that each laboratory manager will
choose the most appropriate procedures, depending on the type and
size of the laboratory in question. Accreditation bodies will not
expect the introduction of all measures, only those that are appropri
ate for a particular laboratory.
N.F. Lightfoot
Newcastle
E.A. Maier
Brussels
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List of contributors
N.F. Lightfoot
Public Health Laboratory Service, Newcastle upon Tyne, U.K.
E.A. Maier
European Commission, DG XII Measurement and Testing
Programme, Brussels, Belgium
H. Beckers
Unilever Research Laboratory, Vlaardingen, Netherlands
S. Dahms
Institut fur Biometrie der freien Universitdt Berlin, Berlin, Germany
J.M. Delattre
Institut Pasteur de Lille, Lille, France
A. Havelaar
National Research Institute of Public Health & Environmental
Protection (RFVM), Bilthoven, Netherlands
M. Michels
Unilever Research Laboratory, Vlaardingen, Netherlands
S. Niemela
University of Helsinki, Helsinki, Finland
J. Papadakis
Athens School of Hygiene, Athens, Greece
D. Roberts
Food Hygiene Reference Laboratory, Central Public Health
Laboratory, London, U.K.
H. Tillett
Communicable Disease Surveillance Centre, Public Health
Laboratory Service Board, London, U.K.
H.R. Veenendaal
KIWA NV, Nieuwegein, Netherlands
H. Weiss
Institut fur Biometrie der freien Universitdt Berlin, Berlin,
Germany