Guidelines for the Interpretation of Results of Microbiological Analysis of Some Ready-To-Eat Foods Sampled at Point of Sale

Transcription

1 Guidelines for the Interpretation of Results of Microbiological Analysis of Some Ready-To-Eat Foods Sampled at Point of Sale Guidance Note No. 3

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3 Guidelines for the Interpretation of Results of Microbiological Analysis of Some Ready-To-Eat Foods Sampled at Point of Sale Published by: Food Safety Authority of Ireland Abbey Court Lower Abbey Street Dublin 1 Tel: Fax: info@fsai.ie Website: Applications for reproduction should be made to the FSAI Information Unit ISBN

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5 Other Food Safety Guidance Notes available from the Food Safety Authority of Ireland: Guidance Note No 1 Inspection of a Food Business (2000) ISBN Guidance Note No 2 Classification of Food (2001) ISBN

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7 Contents INTRODUCTION 1 BACKGROUND 2 MICROBIOLOGICAL CRITERIA 2 GUIDELINES FOR MICROBIOLOGICAL ENFORCEMENT 3 READY-TO-EAT FOODS 4 INTERPRETATION OF GUIDELINES 4 REVISED GUIDELINES 4 MICROBIOLOGICAL QUALITY LEVELS 5 INDICATOR ORGANISMS 6 PATHOGENS 7 TABLE 1: GUIDELINES FOR THE MICROBIOLOGICAL QUALITY 8 OF SOME READY-TO-EAT FOODS AT POINT OF SALE TABLE 2: AEROBIC COLONY COUNT CATEGORIES FOR 9 DIFFERENT TYPES OF READY-TO-EAT FOODS REFERENCES 11 ACKNOWLEDGEMENTS 12

8 Introduction The Food Safety Authority of Ireland Act, 1998, facilitated the establishment of the Food Safety Authority of Ireland (FSAI) to perform the functions assigned to it by this Act. The principal function of the Authority shall be to take all reasonable steps to ensure that: (a) (b) food produced in the State (whether or not distributed or marketed in the State), and food distributed or marketed in the State, meets the highest standards of food safety and hygiene reasonably attainable and it shall, in particular, take all reasonable steps to ensure that such food complies: 1) with any relevant food legislation in respect of food safety and hygiene standards, or 2) in the absence of any such legislation, with the provisions of generally recognised standards or codes of good practice aimed at ensuring the achievement of high standards of food hygiene and food safety. The FSAI believes that Guidance Notes have a major role to play in helping both the regulators and the food industry achieve a higher degree of compliance with Regulations and with good practice generally. A good, well prepared, Guidance Note must, if it is to achieve these objectives, provide regulators and industry alike with clear guidance towards the application of the relevant legislation. While a Guidance Note is not, of course, a substitute for the Regulations, the FSAI believes that adherence to it should make compliance easier by providing the basis for a high degree of consistency in application of those Regulations. We hope this series of Guidance Notes will meet the aims we have set out here and that they will contribute to the development of the high standards we aim to achieve in the food inspection services. 1

9 Background The Microbiology Sub-committee of the Food Safety Authority of Ireland has undertaken a review of the microbiology guidelines for some ready-to-eat foods sampled at point of sale as they appear in the 1995 report of the former Food Safety Advisory Committee 1. The 1995 guidelines were adapted from guidelines published by the UK Public Health Laboratory Service (PHLS) in The revision and expansion of the PHLS guidelines in and subsequent revision in ,have necessitated the current review by the Microbiology Sub-committee.The following guidelines draw heavily on those of the PHLS. This document does not purport to have any legal standing. The microbiological criteria listed in Table 1 are not statutory standards. Revisions to these guidelines will continue to be made as experience is gained of their value in practice and as additional information becomes available. In addition to these guidelines for ready-to-eat foods sampled at point of sale, there is a supporting document that contains relevant material 5. The supporting document broadly describes the approach to establishing microbiological criteria and food sampling plans for all foods sampled at any point in the food chain. It also includes a summary of the microbiological criteria (standards and guidelines) as listed in current EU legislation. Microbiological Criteria Microbiological criteria are essentially of three types: guidelines, standards and specifications. These terms were originally defined by Codex Alimentarius 6 and have since been redefined both by Codex and other international organisations. They can be described as follows: A microbiological guideline is a criterion which relates to the microbiological condition of the food sample that is applied at any stage of food processing and retailing. It aids in identifying situations requiring attention for food safety or quality reasons. Guidelines arise from many sources - the food industry, enforcement agencies and, national and international committees, and are especially applied to indicator organisms. While guidelines may be written in law they are not legally enforceable, but serve to provide assistance to enforcement agencies in interpreting whether producers are complying with the general policy in relation to standards. 2

10 Guidelines can both complement legally enforceable standards and provide a benchmark in the situations where standards are not considered necessary. A persistent and widespread breach of the guidelines could be an indication of poor manufacturing or handling practice. Guidelines also provide a benchmark against which unacceptable microbial contamination of food can be identified. Guideline levels for microbiological hazards are proposed as a mechanism to identify the maximum level of contamination that is reasonably acceptable and to provide a trigger for remedial action when these levels are exceeded. An adverse health effect is not an inevitable consequence of consumption of foods containing microorganisms above the guideline levels. However, the presence of microorganisms above the guideline levels does indicate that human exposure to particular micro-organisms may occur at undesirable and preventable levels. A microbiological standard is a microbiological criterion contained in a law where compliance is mandatory. The food industry must ensure full compliance with these standards which are monitored by enforcement agencies. A microbiological specification is a microbiological criterion applied to raw materials, ingredients or the end-product which is used in a purchase agreement. Specifications are set by purchasers and are usually more stringent than microbiological standards in order to provide an extra margin of safety. Guidelines for Microbiological Enforcement The purpose of these guidelines is to provide authorised officers with assistance in determining the microbiological quality of various ready-to-eat foods sampled at point of sale. Traditionally, in enforcement situations, microbiological examination has played an important role in evaluating the microbiological safety of food. Food inspection services generally rely on the examination of single food samples rather than statistically based sampling plans. The results from single sample examination may provide evidence that food hygiene regulations have been contravened or provide the basis for additional inspection and/or food sampling. They may also give valuable baseline data (usually where samples form part of a specific survey) which can be used for trend analysis. Where there is routine sampling, the choice of food to be sampled will vary according to the local need, and the occurrence of cases and outbreaks of foodborne illness in the area or nationally. 3

11 Ready-to-Eat Foods All composite foods purchased by or supplied to a consumer for their consumption and which do not require significant further processing other than re-heating or completion of a cooking process are included in the ready-to-eat category. If not consumed immediately, these foods usually require refrigeration to ensure shelf-life. There is considerable variation in the composition of ready-to-eat foods. They range from those containing some ingredients that are uncooked, such as sandwiches, to those that are cooked immediately prior to being provided to the consumer. A list of the more common ready-to-eat foods and their categories are outlined in Table 2. Excluded categories include low water activity foods and other ambient temperature stable foods such as jams, canned food, cured food and food preserved by ph reduction (including pickled foods). Interpretation of Guidelines The figures given in Table 1 are guidelines and not statutory microbiological standards. These guidelines have no legal standing. They are intended for use by food examiners and authorised officers. They may be used to monitor the microbiological quality of a food. The microbiological criteria used in the guidelines can be of prime importance in deciding if a food is unfit or in reinforcing other observations, such as breaches in operational hygiene, and providing reasons to suspect a food may not meet sound public health and hygiene standards. It should be noted that the specification of a criterion for a particular organism does not imply that all foods should be examined for that organism as a matter of routine. Authorised officers should be aware that a number of EU directives contain microbiological criteria for a variety of foodstuffs. Some of these criteria may apply to ready-to-eat foods sampled at point of sale. For convenience, these directives and their criteria are summarised in the supporting document.to ensure correct application of these criteria, the current legislation must be read. In addition, it should be noted that the European Commission s Scientific Committee on Veterinary Measures Relating to Public Health has recently evaluated the legal standards and has expressed an opinion on possible changes 7. Revised Guidelines The following changes have been included in the revised guidelines: 1. The term aerobic plate count has been renamed aerobic colony count and is based on incubation at 30 o C for 48±2h. 4

12 2. Five categories of ready-to-eat foods have been identified (Table 2). To avoid confusion with the 21 EU categories 8 (designated by the numbers 1-21) from the guidelines on Article 14 of Directive 89/397/EEC, the five ready-to-eat categories in this document are designated by the upper case letters A to E. The first four categories are based on a range of aerobic colony counts expected according to the type of product and the processing it has received. The fifth category refers to certain fermented foods for which guidelines for aerobic colony counts may not be applicable. Only foods for which sufficient microbiological data exist are listed in Table 2. When a food which is not listed is submitted for analysis, the food should be assessed as to which of the five categories it best fits into - based on the type of product, the processing it has received and the potential for microbial growth during storage. 3. Four quality levels remain, but the term fairly satisfactory has been renamed acceptable. Hence, the four categories are satisfactory, acceptable, unsatisfactory, and unacceptable/potentially hazardous (see below). 4. New or modified criteria have been included for Enterobacteriaceae, Escherichia coli, Listeria spp., E. coli O157 and other verocytotoxigenic producing E. coli (VTEC), Vibrio cholerae,v. parahaemolyticus, Clostridium perfringens, Bacillus cereus and other pathogenic Bacillus spp. (see sections on indicator organisms and pathogens). Microbiological Quality Levels The classification of satisfactory means that the test results indicate good microbiological quality. The classification of acceptable is suggested to take account of the limitations in microbiological sampling, handling, testing and wide confidence limits in enumeration. Due to these factors, some samples will fall between what is considered satisfactory and unsatisfactory. Samples in the unsatisfactory category indicate that the acceptability threshold has been exceeded. Further sampling may be necessary and the authorised officer may wish to carry out a detailed inspection of premises, food production and handling processes to determine whether hygiene practices for food production or handling are inadequate. The judgement of the authorised officer and the observation of trends will indicate the level of response. In general, the ready-to-eat guidelines are similar to or less stringent than the microbiological standards in the relevant EU Directives 5. If an authorised officer suspects that the product may be in breach of 5

13 the legal criteria, they are advised to consult the relevant directive and inform the relevant authorised officer under the directive in force. There are examples where the ready-to-eat guidelines are more stringent than the criteria in the EU Directives. As these examples only relate to the unsatisfactory category and not to the unacceptable/potentially hazardous category, the issue of possible withdrawal under the ready-to-eat guidelines should not arise (see definition of the unacceptable/potentially hazardous category). The numbers quoted under the heading unacceptable/potentially hazardous represent a potential health hazard to those consuming such food. Samples falling in the unacceptable/potentially hazardous category should prompt a rapid response by the authorised officer and a detailed assessment should take place. Product withdrawal should be an option to be considered in this category only. Indicator Organisms Enterobacteriaceae are included in the revised guidelines as they are useful indicators of hygiene and post-processing contamination of heat processed foods. Coliforms have been the traditional indicator group in this context. Coliforms are those members of the Enterobacteriaceae that ferment lactose and include Enterobacter, most Escherichia, Klebsiella and Citrobacter. Tests for coliform bacteria will only detect organisms capable of fermenting lactose. If large numbers of non-lactose-fermenting bacilli are present, reliance on tests for coliform bacteria may lead to falsely reassuring results. In addition, many food pathogens do not ferment lactose. Enterobacteriaceae is a broader term and includes Escherichia spp., Citrobacter spp., Enterobacter spp., Proteus spp., Salmonella enterica spp., Shigella spp., and Yersinia spp.. Thus, examining a sample for the presence of members of the family Enterobacteriaceae instead of coliforms may give a better indication of the likelihood of the presence of pathogens, as well as providing more accurate information about the handling and storage of the foodstuff. It should be noted that this test is not applicable to fresh fruit, vegetables and salad vegetables. The criteria for Escherichia coli (total) and Listeria spp. (total) have been modified. Quantitative quality levels in the unacceptable/potentially hazardous column have been deleted (Table 1). Additionally, Listeria spp. has been modified to include L. monocytogenes because of the changes to the quantitative criteria for L. monocytogenes (see below). 6

14 Pathogens E. coli O157 and other VTEC have been included. Vibrio cholerae has been included because the European Commission has made several decisions in response to the isolation of this organism from various imported ready-to-eat foods, mainly fishery products and, fruits and vegetables. Vibrio cholerae O1 and O139 are the two serogroups responsible for disease. V. parahaemolyticus in seafood has been retained, but the quantitative quality levels have been modified. The quantitative quality levels for Listeria monocytogenes have been modified and the classification of unsatisfactory is now not applicable in this case. The value of 10 2 cfu/g at point of sale/consumption represents a potential risk to health according to a number of recent opinions and published reports 6. It is recognised that some serotypes/phage types of L. monocytogenes may rarely be associated with human infection, however their presence reflects an inadequate level of hygiene. The European Commission is currently drafting a decision on the control of L. monocytogenes in ready-to-eat foods. This decision will include zero tolerance for some ready-to-eat foods and will take precedence over these guidelines. The Clostridium perfringens quantitative quality level for the satisfactory category is now <20 cfu/g to bring it in line with the levels for other gram positive pathogens. The microbiological criteria have been altered for the Bacillus cereus and other pathogenic Bacillus spp. to take account of the minimum infective dose (of >10 5 /g) in the case of the diarrhoeal disease. In the case of the emetic disease, the minimum number of cells required in a food to produce the minimum intoxication dose is also >10 5 /g. When present in foods, B. cereus is usually at concentrations of <10 3 /g. Bacillus species other than B. cereus, notably those of the B. subtilus-licheniformis group, have also been implicated in outbreaks of food poisoning from meat and pastry products and, meat or seafood rice dishes. This group is now included in the revised guidelines. Initial isolation and enumeration procedures are similar to those for B. cereus and biochemical tests are necessary for confirmation. 7

15 Table 1: Guidelines for the Microbiological Quality of some Ready-To-Eat Foods at Point of Sale Food Category (see Table 2) Criterion Microbiological quality (cfu per gram unless otherwise stated) (a) Satisfactory Acceptable Unsatisfactory (b) Unacceptable/ potentially hazardous (c) Aerobic colony count (d) 30 o C / 48h A < <10 4 >10 4 N/A B < <10 5 >10 5 N/A C < <10 6 >10 6 N/A D < <10 7 >10 7 N/A E N/A N/A N/A N/A Indicator organisms (e) A-E Enterobacteriaceae (f) < <10 4 >10 4 N/A A-E Escherichia coli (total) <20 20-<100 >100 N/A A-E Listeria spp. (total) <20 20-<100 >100 N/A Pathogens A-E Salmonella spp Not detected Detected in 25g in 25g A-E Campylobacter spp. Not detected Detected in 25g in 25g A-E E. coli O157 & other VTEC Not detected Detected in 25g in 25g A-E Vibrio cholerae Not detected Detected in 25g in 25g A-E Vibrio parahaemolyticus (g) <20 20-< <10 3 >10 3 A-E L. monocytogenes <20 (h) 20-<100 N/A >100 A-E Staphylococcus aureus <20 20-< <10 4 >10 4 A-E Clostridium perfringens <20 20-< <10 4 >10 4 A-E Bacillus cereus & other pathogenic Bacillus spp. (i) < < <10 5 >10 5 (a) For a detailed explanation of the categories of microbiological quality see page 6. (b) Further sampling may be necessary and the authorised officer may wish to initiate a detailed inspection by the relevant authorised officer of premises, food production and handling processes to determine whether hygiene practices for food production or handling are inadequate. (c) Product withdrawal should be an option to be considered in this category only. (d) Guidelines for aerobic colony counts may not apply to certain fermented foods - e.g. salami, soft cheese and unpasteurised yoghurt. These foods fall into Category E (see Table 2). Acceptability is based on appearance, smell, texture and the levels or absence of indicator organisms or pathogens. (e) On occasion some strains may be pathogenic. (f) Enterobacteriaceae are indicators of hygiene and of post-processing contamination of heat processed foods. They are not applicable to fresh fruit, vegetables and salad vegetables. (g) Relevant to seafood only. (h) Not detected in 25g for certain long shelf-life products under refrigeration, such as soft ripened cheese, vacuum packed paté and sliced meats. (i) If the Bacillus counts exceed 10 4 per gram, the organism should be identified. N/A Denotes not applicable. 8

16 Table 2: Aerobic Colony Count Categories for Different Types of Ready-To-Eat Foods Food Group Product Category (A-E) Dairy cheese E ice-cream, milk shakes (non-dairy) B ice lollies, slush and sorbet B yogurt/frozen yogurt (natural) E Dessert cakes, pastries, slices and desserts - with dairy cream C cakes, pastries, slices and desserts - without dairy cream B cheesecake E mousse/dessert A tarts, flans and pies B trifle C Meat beefburgers A ham - raw (e.g. Parma) E kebabs B meat meals (shepherds/cottage pie/casseroles) B meat pies (steak and kidney, pastry) A meat, sliced (beef, pork, poultry) C meat, sliced (cooked ham, tongue) D pork pies A poultry (unsliced) B salami and fermented meat products E sausage roll A sausages (smoked) E scotch egg A Ready-to-Eat pasta/pizza B Meals meals (other) B Sandwiches and with cheese E Filled Rolls with salad E without salad D Savoury bean curd E bhaji (onion, spinach, vegetable) A cheese-based bakery products B fermented foods E flan/quiche B homous, tzatziki and other dips D mayonnaise/dressings B paté (meat, seafood or vegetable) C samosa B satay C spring rolls C 9

17 Table 2: Aerobic Colony Count Categories for Different Types of Ready-To-Eat Foods Food Group Product Category (A-E) Seafood crustaceans (crab, lobster, prawns) C herring and other raw pickled fish A molluscs and other shellfish (cooked) D other fish (cooked) C seafood meals C smoked fish D taramasalta D Vegetable coleslaw C fruit and vegetables (dried) C fruit and vegetables (fresh) E prepared mixed salads and crudités D rice C vegetables and vegetable meals (cooked) B 10

18 References 1 Food Safety Advisory Committee (1995). Microbiological Standards Limits and Guidelines for Foods. Report to the Minister for Health and the Minister for Agriculture, Food and Forestry (Stationary Office, Dublin). Report No. 21, April Public Health Laboratory Service (1992). Provisional microbiological guidelines for some ready-to-eat foods sampled at point of sale. Notes for PHLS examiners. PHLS Microbiological Digest 9: Public Health Laboratory Service (1996). Microbiological guidelines for some ready-to-eat foods sampled at the point of sale: an expert opinion from the PHLS. PHLS Microbiology Digest 13, (1), Public Health Laboratory Service (2000). Guidelines for the microbiological quality of some ready-to-eat foods at the point of sale. Comm Dis Public Health 3, (3), Microbiology Sub-committee (2001). Material Relevant to Guidelines for the Interpretation of Results of Microbiological Analysis of Some Ready-To-Eat Foods Sampled at Point of Sale. Food Safety Authority of Ireland. 6 Codex Alimentarius Commission (1981). Report of the 17th Session of the Codex Committee on Food Hygiene,Washington DC November ALINORM 81/13 Appendix II. Codex Alimentarius Commission, FAO Rome. 7 Scientific Committee on Veterinary Measures relating to Public Health (1999). Opinion on L. monocytogenes. European Commission. Health & Consumer Protection Directorate-General. Directorate B - Scientific Health Opinions. 8 Guidance Note No. 2, Classification of Food (2001). Food Safety Authority of Ireland. 11

19 Acknowledgements The Food Safety Authority of Ireland is most grateful for the advice and co-operation of the Public Health Laboratory Service Environmental Surveillance Unit of the Communicable Disease Surveillance Centre at Colindale, London, UK in the preparation of these Guidelines. The FSAI is particularly grateful for the categorisation of foods (Table 2) which is the result of the work of that Unit. 12

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24 Food Safety Authority of Ireland Abbey Court, Lower Abbey Street, Dublin 1 Údarás Sábháilteachta Bia na héireann Cúirt na Mainistreach, Sráid na Mainistreach Íocht., Baile Átha Cliath 1 Telephone: Facsimile: info@fsai.ie Website: ISBN