MICROBIOLOGICAL EXAMINATION METHODS OF FOOD AND WATER

Transcription

1 ITAL, MICROBIOLOGICAL EXAMINATION METHODS OF FOOD AND WATER A Laboratory Manual NEUSELY DA SILVA, MARTA HIROMITANIWAKI, VALERIA CHRISTINA AMSTALDEN JUNQUEIRA, NELIANE FERRAZ DE ARRUDA SILVEIRA, MARISTELA DA SILVA DO NASCIMENTO & RENATO ABEILAR ROMEIRO GOMES Institute of Food Technology - Campinas, SP, Brazil CRC Press Taylor * Francis Group Boca Raton London New York Leiden CRC Press is an imprint of the Taylor & Francis Croup, an informa business A BALKEMA BOOK

2 Table of contents Preface About the authors List of tables List of figures XVII XIX XXI XXV 1 Sampling, transport and storage of samples for analysis 1.1 Introduction Lot Lot sample and sample unit Lot sampling plans The two-class sampling plan The three-class sampling plan Analytical unit Collecting samples for analysis Selection and preparation of containers for the sampling of foods contained in non-individual packages Procedures for the sampling of foods contained in non-individual packages Sampling of foods involved in foodborne diseases Sampling of water Transportation and storage of samples until analysis Foods with low water activity Frozen foods Refrigerated foods Commercially sterile foods in sealed packages Water samples References 7 2 Preparation of sample for analysis Introduction Homogenization of samples and withdrawal of the analytical unit Procedure for homogenization and withdrawal of analytical units from liquid products Procedure for homogenization and withdrawal of analytical units from solid or concentrated liquid products Procedure for withdrawing the analytical unit using the surface swabbing technique Swab sampling Sponge sampling Procedure for withdrawing the analytical unit using the surface washing technique Procedure for washing poultry carcasses Procedure for washing other foods Procedure for washing packages Keeping of counter-samples Preparation of the first dilution of the analytical unit Diluents for presence/absence tests Diluents for tests requiring differentiated handling of the sample 15

3 VI Table of contents Diluents for general quantification tests How to prepare an initial 1:10 (10~') dilution How to an prepare initial dilution different from 1: Procedure for the preparation of the first dilution of liquid samples Procedure for the preparation of the first dilution of solid or concentrated liquid samples Procedure for the preparation of the first dilution of samples obtained by surface swabbing or surface washing Serial decimal dilution of the sample References 17 Annex 2.1 Procedures for the homogenization of the content and withdrawal of the analytical unit of different types of foods 18 Annex 2.2 Special cases in which there are variations in the analytical unit and/or dilution and/or diluents recommended for the preparation of the first dilution of samples of different types of foods 19 3 Basic plate count techniques for the enumeration of microorganisms Introduction Pour plate technique Material required for the analyses Procedure Spread plate technique Material required for the analyses Procedure Drop plate technique Material required for the analyses Procedure Membrane filtration Material required for the analyses Procedure Counting colonies and calculating results Pour plate calculations Calculating the pour plate Calculating the pour plates results for samples prepared by the surface results in the standard situation 30 swabbing technique (swabs or sponges) Calculating the pour plate results for samples prepared by the surface washing technique Spread plate calculations Drop plate calculations Membrane filtration calculations Counting colonies and calculating results according to ISO 7218: References 37 4 Basic techniques for microbial enumeration by the most probable number method (MPN) Introduction Multiple dilution test Material required for the analyses Single Procedure 41 dilution test Material required for the analyses 42

4 Table of contents VII Procedure Calculation of the results Calculating the results of the multiple dilution test Calculation using the MPN tables (for decimal dilutions) 43 AAA.2 Calculating using the Thomas formula (for non-decimal dilutions) 44 AAA.3 Calculating the results for samples prepared by the surface swabbing or surface washing techniques Calculating the results of the single dilution test Rules for calculations performed using the MPN-3 Table Calculation for samples prepared by the surface swabbing or surface washing techniques References 45 Annex MPN tables 46 5 Basic techniques for the detection of the presence/absence of microorganisms Introduction Enrichment Pre-enrichment Selective enrichment Isolation in solid media (selective differential plating) Confirmation Catalase test Citrate test Amino acid decarboxylation tests Phenylalanine deaminase test Carbohydrate fermentation tests Indole test Malonate test Oxidation/Fermentation test (O/F) Oxidase test Nitrate reduction test Urease test Methyl Red test (MR) Voges-Proskauer test (VP) Material required for the analyses Procedure Pre-enrichment Selective enrichment Selective differential plating Streak plating technique for obtaining pure cultures Selection of colonies and subculturing of cultures for confirmation Technique for the subculturing of pure cultures starting from colonies isolated from plates Confirmation tests Gram-staining (Hucker's method) Spore-staining (Schaeffer-Fulton's method) Spore-staining (Ashby's method) Wet mounts for direct (fresh) microscopic observation References 56

5 VIII Table of contents 6 Aerobic plate count Introduction The importance and significance of the total aerobic mesophilic count Definition of psychrotrophics Methods of analysis Plate count method APHA 2001 for aerobic mesophilic bacteria in foods and water Material required for analysis Procedure Pour plate technique Spread plate technique Membrane filtration technique Petrifilm AOAC official methods for aerobic mesophilic bacteria in foods Material required for analysis Procedure Plate count method APHA 2001 for aerobic psychrotrophic bacteria in foods Material required for analysis Procedure References 65 7 Yeasts and molds Introduction Yeasts and molds in foods Methods of analysis for total yeast and mold counts Psychrotrophic fungi Heat-resistant molds Preservative-resistant yeasts (PRY) Zigosaccharomyces bailii (Lindner) Guilliermond Zygosaccharomyces bisporus (Naganishi) Lodder and Kreger Schizosaccharomycespombe Lindner Candida krusei (Castellani) Berlchout Pichia membranaefaciens Hansen Osmophilic yeasts Zygosaccharomyces rouxii (Boutroux) Yarrow Plate count method APHA 2001 for yeasts and molds in foods Material required for analysis Procedure Plate count method APHA 2001 for psychrotrophic fungi in foods Material required for analysis Procedure Plate count method APHA 2001 for heat-resistant molds in foods Material required for analysis Procedure Presence/absence method Pitt and Hocking 2009 and Plate count method Pitt and Hocking 2009 for preservative-resistant yeasts in foods Material required for analysis Procedure Membrane filtration method APHA 2001 and Plate count method APHA 2001 for osmophilic yeasts in foods Material required for analysis Procedure References 81

6 Table of contents IX 8 Enterobacteriaceae Introduction Taxonomy Methods of analysis Plate count method APHA 2001 for Enterobacteriaceae in foods Material required for analysis Procedure Most probable number (MPN) method APHA 2001 for Enterobacteriaceae in foods Material required for analysis Procedure Petrifilm AOAC official method for Enterobacteriaceae in selected foods Material required for analysis Procedure References 88 9 Total and thermotolerant coliforms and Escherichia coli Introduction Definition of total coliforms Definition of thermotolerant coliforms Escherichia coli Use as indicators Methods of analysis Most probable number (MPN) method APHA 2001 for total coliforms, thermotolerant coliforms and E. coli in foods Material required for analysis Procedure Most probable number (MPN) methods ISO 4831:2006 and ISO 7251:2005 for total coliforms and presumptive E. coli in foods Material required for analysis Procedure Most probable number (MPN) method APHA/AWWA/WEF 2005 for total and thermotolerant coliforms and E. coli in water Material required for analysis Procedure Plate count method APHA 2001 for total coliforms in foods Material required for analysis Procedure References Staphylococcus aureus Introduction Taxonomy The genus Staphylococcus The coagulase positive staphylococci Staphylococcus aureus Pathogenicity Staphylococcus aureus enterotoxins Staphylococcal food poisoning Methods of analysis Plate count method APHA 2001 for coagulase positive staphylococci and S. aureus in foods Material required for analysis Procedure 110

7 X Table of contents 10.3 Most probable number (MPN) method APHA 2001 for coagulase positive staphylococci and S. aureus in foods Material required for analysis Procedure Presence/absence method APHA 2001 for coagulase positive staphylococci and S. aureus in foods Material required for analysis Procedure References Bacillus cereus Introduction B. cereus Group Main characteristics of B. cereus Methods of analysis Plate count method APHA 2001 for Bacillus cereus in foods Material required for analysis Procedure Most probable number (MPN) method APHA 2001 for Bacillus cereus in foods Material required for analysis Procedure References Clostridium perjringens Introduction Main characteristics of C. perjringens Epidemiology C. perjringens type A food poisoning C. perjringens type C necrotic enteritis Methods of analysis Plate count method APHA 2001 for Clostridium perjringens in foods Material required for analysis Procedure Presence/absence method APHA 2001 for Clostridium perjringens in foods Material required for analysis Procedure References Enterococci Introduction Enterococci Species of intestinal origin Species found in plants, soil and water Species found in foods Biochemical characteristics of the genus Enterococcus Fecal streptococci Biochemical characteristics of the genus Streptococcus Diferentiation of enterococci from fecal streptococci Methods of analysis 142

8 Table of contents XI 13.2 Plate count method APHA 2001 for enterococci and fecal streptococci in foods Material required for analysis Procedure Most probable number (MPN) method APHA 2001 for enterococci and fecal streptococci in foods Material required for analysis Procedure Membrane filtration method APHA/AWWA/WEF 2005 for enterococci and fecal streptococci in water Material required for analysis Procedure Membrane filtration method ISO :2000 for intestinal enterococci in water Material required for analysis Procedure References Lactic acid bacteria Introduction Carnobacterium Collins et al Enterococcus (ex Thiercelin & Jouhaud 1903) Schleifer & Kilpper-Biilz Fructobacillus Endo and Okada Lactobacillus Beijerinck 1901 emend. Haakensen et al Lactococcus Schleifer et al Leuconostoc van Tieghem Oenococcus Dicks et al emend. Endo and Okada Pediococcus Balcke Rosenbach Streptococcus Tetragenococcus Collins et al Weissella Collins et al Methods of analysis Plate count method APHA 2001 for lactic acid bacteria in foods Material required for analysis Procedure Most probable number (MPN) methods APHA 2001 for lactic acid bacteria in foods Material required for analysis Procedure using the MRS broth 162 SL Broth Procedure using the Rogosa 14.4 References Campylobacter Introduction Taxonomy Epidemiology Presence/absence method ISO :2006 for thermotoleranr Campylobacter in foods Material required for analysis Procedure References Cronobacter Introduction Taxonomy 175

9 XII Table of contents Cronobacter Iversen et al. 2008, gen. nov Epidemiology Codex Alimentarius microbiological criteria for Cronobacter spp. in powdered infant formulae Presence/absence method ISO 22964:2006 for Cronobacter [Enterobacter sakazakii] in milk powder and powdered infant formula Material required for analysis Procedure References Pseudomonas Introduction Taxonomy Pseudomonas MigiAa Shewanella MacDondl & Colwell Janthinobacterium De Ley et al emend. Lincoln et al Stenotrophomonas Palleroni & Bradbury Most probable number (MPN) method APHA/AWWA/WEF 2005 for Pseudomonas aeruginosa in water Material required for analysis Procedure Membrane filtration method ISO 16266:2006 for Pseudomonas aeruginosa in water A Material required for analysis Procedure Plate count method ISO 13720:2010 for presumptive Pseudomonas spp. in meat and meat products Material required for analysis Procedure Plate count method ISO 11059:2009 IDF/RM 225:2009 for Pseudomonas spp. in milk and milk products Material required for analysis Procedure References Listeria monocytogenes Introduction Taxonomy Epidemiology Methods of analysis Presence/absence method BAM/FDA 2011 for Listeria monocytogenes in foods Material required for analysis Procedure Presence/absence method MLG/FSIS/USDA 2009 for Listeria monocytogenes in foods Material required for analysis Procedure Plate count method ISO :1998 Amendment 1:2004 for Listeria monocytogenes in foods Material required for analysis Procedure Presence/absence method ISO :1996 Amendment 1:2004 for Listeria monocytogenes in foods Material required for analysis Procedure References 214

10 Table of contents XIII 19 Salmonella Introduction Taxonomic classification of Salmonella Serological classification of Salmonella Biochemical characteristics of Salmonella Epidemiology Traditional methods used for the examination of Salmonella Alternative methods for the analysis of Salmonella Composite samples for analysis Presence/absence method ISO 6579:2002 Amendment 1:2007 for Salmonella in foods Material required for analysis Procedure Presence/absence method BAM/FDA 2011 for Salmonella in foods Material required for analysis Procedure Presence/absence method MLG/FSIS/USDA 2011 for Salmonella in foods Material required for analysis Procedure References Vibrio cholerae and Vibrio parahaemolyticus Introduction Taxonomy Epidemiology V. cholerae V. parahaemolyticus V. vulnificus Methods of analysis Presence/absence method APHA 2001 and BAM/FDA 2004 for Vibrio cholerae in foods Material required for analysis Procedure Most probable number (MPN) method APHA 2001 and BAM/FDA 2004 for Vibrio parahaemolyticus in foods Material required for analysis Procedure Presence/absence method ISO :2007 for presumptive enteropathogenic Vibrio cholerae and Vibrio parahaemolyticus in foods Material required for analysis Procedure References Yersinia enterocolitica Introduction Taxonomy Epidemiology Presence/absence method ISO 10273:2003 for presumptive pathogenic Yersinia enterocolitica in foods Material required for analysis Procedure References 275

11 XIV Table of contents 22 Bacterial spore count Introduction The bacterial spore Sequence of spore formation Spore ultrastructure Mechanisms of spore resistance Taxonomy of sporeforming bacteria important in foods Aeribacillus Minana-Galbis et al Alicyclobacillus Wisotzkey et al emend. Goto et al emend. Karavaiko et al Aneurinibacillus Shida et al emend. Heyndrickx et al Anoxybacillus Pikuta et al emend. Pikuta et al Bacillus Cohn Brevibacillus Shida et al Clostridium Prazmowski Cohnella Kampfer et al Desulfotomaculum Campbell and Postgate Geobacillus Nazina et al Jeotgalibacillus Yoon et al emend. Chen et al Lentibacillus Yoon et al emend. Jeon et al Lysinibacillus Ahmed et al Moorella Collins et al Oceanobacillus Lu et al emend. Lee et al Paenibacillus Ash et al emend. Shida et al Sporolactobacillus Kitahara and Suzuki Thermoanaerobacter Wiegel and Ljungdahl 1982 emend. Lee et al Tbermoanaerobacterium Lee et al Virgibacillus Heyndrickx et al emend. Wain et al emend. Heyrman et al Methods APHA 2001 for spores of total and "flat sour" thermophilic aerobic sporeformers in foods Material required for analysis Procedure for the analysis of sugar Procedure for the analysis of starch Procedure for the analysis of whole tomatoes, tomato pulp, tomato puree and concentrated milk Procedure for the analysis of nonfat dry milk Procedure for the analysis of milk cream Procedure for the analysis of other foods and ingredients (general) Methods APHA 2001 for spores of thermophilic anaerobic sporeformers in foods Material required for analysis Procedure for the analysis of sugar and powdered milk Procedure for the analysis of starches and flours Procedure for the analysis of cereals and alimentary pastes Procedure for the analysis of fresh mushrooms Procedure for the analysis of "in-process" products Methods APHA 2001 for spores of sulfide spoilage anaerobic sporeformers in foods Material required for analysis Procedure for the analysis of sugar Procedure for the analysis of starch and flour 298

12 Table of contents XV Procedure for the analysis of skim milk powder Procedure for the analysis of soy protein isolates Methods APHA 2001 for spores of mesophilic aerobic sporeformers in foods Material required for analysis Procedure for foods in general Procedure for the analysis of milk and dairy products Procedure for the analysis of water Methods APHA 2001 for spores of mesophilic anaerobic sporeformers in foods Material required for analysis Procedure for the analysis of sugar Procedure for the analysis of starch, flours and other cereal products Procedure for the analysis of dehydrated vegetables Procedure for the analysis of seasonings and spices Procedure for the analysis of egg powder, milk powder and other powdered dairy products Procedure for the analysis of fluid milk and cheeses Other procedures for mesophilic anaerobic sporeformers Methods IFU 12:2007 for Alicyclobacillus in foods Material required for analysis Procedure for the analysis of raw material Procedure for analysis of the finished product Interpretation and calculation of the results References Commercial sterility Introduction Parameters for evaluating the heat resistance of microorganisms Survival curve and decimal reduc-ion time (D value) Number of decimal reductions Thermal destruction curve and temperature coefficient (z value) D and z values of microorganisms of importance in foods Dimensioning heat treatments and thermal processing Microbial spoilage of canned foods Method APHA 2001 for commercial sterility or cause of spoilage of low acid canned foods Material required for analysis Procedure Interpretation of the results Method APHA 2001 for commercial sterility or cause of spoilage of acid canned foods Material required for analysis Procedure Interpretation of the results References Guidelines on preparation of culture media Introduction Ingredients used in the formulation of culture media Water for preparing media and reagents Nutrient sources for culture media Selective agents Differential agents 338

13 Sampling XVI Table of contents Reducing agents Buffering agents Chromogenic and fluorogenic substrates Agar Types of culture media Procedure for the preparation of culture media Storing supplies and ingredients for preparation of culture media Weighing and rehydration Dissolution and dispersion Verification and adjustment of the ph before sterilization Distribution Sterilization by moist heat Sterilization by filtration Verification after sterilization Preparation of supplements for culture media Storage of sterilized media until the moment of use Preparation of the media at the moment of use References 345 Annex 1 - Preparation of media and reagents 347 Annex 2 - plans and microbiological limits recommended by ICMSF for foods 437 Subject index 445