Statistical Aspects of the Microbiological Examination of Foods

Title:

Personal Author:

Jarvis, B. (Basil), 1936-, author

Edition:

Third edition

Physical Description:

xiv, 327 pages : illustrations ; 24 cm.

ISBN:

9780128039731

Abstract:

This "Third Edition updates some important statistical procedures... Following a brief introduction to the subject, basic statistical concepts and procedures are described including both theoretical and actual frequency distributions that are associated with the occurrence of microorganisms in foods. This leads into a discussion of the methods for examination of foods and the sources of statistical and practical errors associated with the methods. Such errors are important in understanding the principles of measurement uncertainty as applied to microbiological data and the approaches to determination of uncertainty. The ways in which the concept of statistical process control developed many years ago to improve commercial manufacturing processes can be applied to microbiological examination in the laboratory. This is important in ensuring that laboratory results reflect, as precisely as possible, the microbiological status of manufactured products through the concept and practice of laboratory accreditation and proficiency testing. The use of properly validated standard methods of testing and the verification of 'in house' methods against internationally validated methods is of increasing importance in ensuring that laboratory results are meaningful in relation to development of and compliance with established microbiological criteria for foods. [Finally], the book reviews the uses of such criteria in relation to the development of and compliance with food safety objectives. Throughout the book the theoretical concepts are illustrated in worked examples using real data obtained in the examination of foods and in research studies concerned with food safety."

Subject Term:

Food -- Microbiology -- Technique -- Statistical methods

Food -- Analysis -- Statistical methods

Microorganisms -- Identification -- Statistical methods

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Library	Item Barcode	Call Number	Material Type	Item Category 1	Status
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Summary

Statistical Aspects of the Microbiological Examination of Foods, Third Edition , updates some important statistical procedures following intensive collaborative work by many experts in microbiology and statistics, and corrects typographic and other errors present in the previous edition. Following a brief introduction to the subject, basic statistical concepts and procedures are described including both theoretical and actual frequency distributions that are associated with the occurrence of microorganisms in foods. This leads into a discussion of the methods for examination of foods and the sources of statistical and practical errors associated with the methods. Such errors are important in understanding the principles of measurement uncertainty as applied to microbiological data and the approaches to determination of uncertainty.

The ways in which the concept of statistical process control developed many years ago to improve commercial manufacturing processes can be applied to microbiological examination in the laboratory. This is important in ensuring that laboratory results reflect, as precisely as possible, the microbiological status of manufactured products through the concept and practice of laboratory accreditation and proficiency testing. The use of properly validated standard methods of testing and the verification of 'in house' methods against internationally validated methods is of increasing importance in ensuring that laboratory results are meaningful in relation to development of and compliance with established microbiological criteria for foods.

The final chapter of the book reviews the uses of such criteria in relation to the development of and compliance with food safety objectives. Throughout the book the theoretical concepts are illustrated in worked examples using real data obtained in the examination of foods and in research studies concerned with food safety.

Author Notes

Prof. Basil Jarvis has held various academic and senior industrial research positions throughout his career as a food microbiologist. His work has taken him to many countries outside the UK including the USA, Scandinavia and South Africa. He has published widely on food quality and safety, including inhibition of microbes in food systems, microbial toxins in foods, rapid microbiological methods, and statistical aspects of food microbiology. For almost 40 years he has been a Visiting Professor at the University of Reading and for 20 years was an Honorary Professor of Life Sciences at the University of Surrey, where he established a WHO-sponsored graduate course in Food Microbiology for medical and veterinary practitioners.

He has served on numerous official advisory groups, including the statistics group of the AOAC Presidential Taskforce on 'Best Practices in Microbiological Methods'. He is also a member of the ISO working group on Microbiological Statistics. He is a Past President and Honorary Member of the Society for Applied Microbiology, a Fellow of the Royal Society of Biology and a Fellow of the Institute for Food Science and Technology. Although now retired, he retains his interests in teaching students and considers statistics to be a relaxing hobby, especially when accompanied by a glass of fine wine!

List of Tables	p. xi
List of Figures	p. xv
List of Examples	p. xix
Preface to the Third Edition	p. xxiii
Chapter 1 Introduction	p. 1
Chapter 2 Some Basic Statistical Concepts	p. 3
Populations	p. 3
Lots and Samples	p. 3
Average Sample Populations	p. 5
Statistics and Parameters	p. 9
Variance and Error	p. 9
The Central Limit Theorem	p. 10
References	p. 12
General Reading	p. 12
Chapter 3 Frequency Distributions	p. 13
Types of Frequency Distribution	p. 16
Statistical Probability	p. 20
The Binomial Distribution (¿ 2	p. 23
Multinomial Distribution	p. 25
The Normal Distribution	p. 27
The Poisson Distribution (¿ 2	p. 28
The Negative Binomial Distribution (¿ 2	p. 33
Relationships Between the Frequency Distributions	p. 39
Transformations	p. 39
References	p. 45
Chapter 4 The Distribution of Microorganisms in Foods in Relations to Sampling	p. 47
Random Distribution	p. 49
Tests for Agreement with a Poisson Series	p. 49
Regular Distribution	p. 57
The Binomial Distribution as a Model for a Regular Dispersion	p. 58
Contagious (Heterogeneous) Distributions	p. 58
The Negative Binomial as a Model for Contagious Distribution	p. 59
The Lognormal and Oilier Contagious Distribution Models	p. 62
Effects of Sample Size	p. 64
References	p. 69
Chapter 5 Statistical Aspects of Sampling for Microbiological Analysis	p. 71
Attributes and variables Sampling	p. 71
Binomial and Trinomial Distributions	p. 73
The Binomial Distribution (Two-Class Sample Plan)	p. 73
The Trinomial Distribution (Three-Class Sample Plans)	p. 76
Precision of the Sample Estimate	p. 77
Valuation in Sample Size	p. 78
Acceptance Sampling by Attributes	p. 78
Two-Class Plans	p. 83
Three-Class Plans	p. 86
Operating Characteristics (OC) Curves	p. 90
Acceptance Sampling by Variables	p. 91
Some Statistical Considerations About Drawing Representative Samples	p. 96
Stratified Sampling	p. 98
Sampling Frames	p. 99
Single or Multiple Sampling Schemes	p. 99
Addendum	p. 99
References	p. 100
Chapter 6 Errors Associated with Preparing Samples for Analysis	p. 103
Laboratory Sampling Errors	p. 103
Diluent Volume Errors	p. 104
Pipette Volume Errors	p. 105
Other Sources of Error	p. 108
Calculation of the Relative Dilution Error	p. 109
Effects of Gross Dilution Series Errors on the Derived Colony Count	p. 117
References	p. 117
Chapter 7 Errors Associated with Colony Count Procedures	p. 119
Specific Technical Errors	p. 119
Pour Plate and Similar Methods	p. 119
Surface Plating Methods	p. 120
Pipetting and Distribution Errors	p. 122
Pipette Errors	p. 122
Distribution Errors	p. 122
Limiting Precision and Confidence Limits of the Colony Count	p. 126
General Technical Errors	p. 132
Incubation Errors	p. 132
Counting Errors	p. 132
Worker's Error	p. 134
Comparability of Colony Count Methods	p. 134
Overall Error of Colony Count Methods	p. 135
References	p. 138
Chapter 8 Errors Associated with Quantal Response Methods	p. 141
Dilution Series and Most Probable Number Counts	p. 141
Single-Tube Dilution Tests	p. 143
Multiple Tests at a Single Dilution Level	p. 145
Multiple Test Dilution Series	p. 146
Multiple Tests at Several Dilution Levels	p. 146
Stevens' Method for Multiple Dilution Levels	p. 147
The Most Probable Number Method for Multiple Dilution Levels	p. 147
Differences Between MPN Values	p. 157
Special Applications of Multiple-Tube Dilution Tests	p. 158
Quantification Based on Relative Prevalence of Defectives	p. 160
Other Statistical Aspects of Multistage Tests	p. 161
The Test Procedure	p. 161
Compositing of Samples	p. 163
Selection of Colonies for Identification	p. 166
References	p. 168
Chapter 9 Statistical Considerations of Other Methods in Quantitative Microbiology	p. 171
Direct Microscopic Methods	p. 171
Howard Mould Count	p. 174
Electrical Counting of Cells (Flow Cytometry)	p. 174
Indirect Methods	p. 175
Impedance Methods	p. 175
Real-Time Polymerase Chain Reaction Methods	p. 178
RT-qPCR	p. 181
References	p. 182
Chapter 10 Measurement Uncertainty in Microbiological Analysis	p. 185
Accuracy, Trueness and Precision	p. 186
Measurement Uncertainty	p. 187
How is Uncertainty Estimated?	p. 188
Reporting of Uncertainty	p. 191
Sampling Uncertainty	p. 191
References	p. 192
Chapter 11 Estimation of Measurement Uncertainty	p. 195
The 'Generalised Uncertainty Method' of 'Bottom-Up' Procedure	p. 195
Rums Associated with the Microbial Distribution in the Sample Matrix	p. 195
Errors Associated with the Sampling Process	p. 196
Errors Associated with use of a Microbiological Method	p. 196
The 'Top-Down' Approach to Estimation of Uncertainty	p. 198
Analysis of Variance	p. 199
Tests for 'Normality'	p. 199
Tests for Outliers	p. 200
The Standard ANOVA Procedure	p. 204
Robust Methods of ANOVA	p. 207
Measurement of Intermediate Reproducibility	p. 214
Matrix and Other Effects	p. 215
Estimation of Uncertainly Associated with Quantal Methods	p. 216
Estimation of Variance Based on Binomial Distribution	p. 216
MPN Estimates	p. 221
Level of Detection Estimates	p. 222
Use of Reference Materials in Quantal Testing	p. 224
References	p. 224
Chapter 12 Statistical Process Control Using Microbiological Data	p. 229
What is Statistical Process Control?	p. 229
Trend Analysis	p. 230
Tools for Statistical Process Control	p. 230
SPC Performance Standards	p. 232
Setting Control Limits	p. 233
Shewhart's Control Charts for Variables Data	p. 235
X and R Charts	p. 235
X and s Charts	p. 236
Interpretation of x, s and R Charts	p. 237
CUSUM Charts	p. 247
The CUSUM Signal Chart	p. 247
The Moving Windows Average	p. 255
Control Charts for Attribute Data	p. 257
Recent Developments in Statistical Process Control	p. 264
References	p. 265
Chapter 13 Validation of Microbiological Methods for Food	p. 267
The Stages or Method Development	p. 268
What is Validation?	p. 269
Harmonisaiion	p. 270
Validation of Qualitative Methods	p. 271
Selectivity Testing	p. 271
Method Comparison	p. 271
Validation of Quantitative Methods	p. 282
Examination of Data for Outliers	p. 282
Graphical Representation of Data	p. 282
Performance Parameters	p. 282
Future Directions	p. 292
References	p. 292
Chapter 14 Risk Assessment and Microbiological Criteria for Foods	p. 295
Risk Assessment and Food Safety Objectives	p. 296
Microbiological Criteria	p. 302
How Should Microbiological Criteria be Set?	p. 304
The Relevance of Measurement Uncertainty to MC	p. 310
Conclusions	p. 315
References	p. 315
Subject Index	p. 321

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Author Notes

Table of Contents