What are the existing microbiological standards and guidelines stipulated in Hong Kong?
The relevant food safety regulation is laid down in the Public Health and Municipal Services Ordinance, Chapter 132 (the Ordinance). Section 54 of the Ordinance stipulates that it is an offence to sell food that is unfit for human consumption. General protection for purchasers of food is provided in Section 52 of the Ordinance when a person may be guilty for selling to the prejudice of a purchaser any food which is not of the nature, substance or quality demanded by the purchaser. Legal microbiological standards for some specified foods e.g. frozen confections and milk are stipulated in its subsidiary legislation.
There is also a set of Microbiological Guidelines for Food. Microbiological Guidelines are criteria indicating the microbiological condition of the food items when there are no established microbiological standards. They also supplement any existing legislative microbiological standards so as to reflect the safety and hygienic quality of the food. The purpose of the Guidelines is to provide assistance to officers in the interpretation of microbiological analyses of foods and give recommendations on the appropriate follow-up action to monitor and control food safety. It also serves to facilitate the trade in devising measures to improve their food safety practices.
How were the Microbiological Guidelines developed?
In 2002, under the advice of the Expert Panel on Microbiological Safety of Food (Expert Panel), a set of Microbiological Guidelines for Ready-to-eat Food was developed by the Food and Environmental Hygiene Department. In light of changing needs and expert advice, the Guidelines were amended in 2007 under the advice of the Expert Panel. Subsequently in 2009, supplementary information to the Guidelines regarding the microbiological criteria for bottled waters and edible ice and the revised microbiological criteria for non-bottled drinks were established under the advice of an Ad Hoc Working Group on Microbiological Safety of Food formed under the Expert Committee on Food Safety (Expert Committee) in 2008.
In order to keep the local microbiological guidelines abreast of the international development and advancement of food science and technology, the Ad Hoc Working Group on Microbiological Safety of Food 2011 (Working Group) was formed under the Expert Committee to provide professional recommendation based on the latest situation. During its development, local stakeholders including trade were consulted. The Guidelines were endorsed by the Expert Committee on Food Safety and submitted to the World Trade Organization for notification.
As compared the "Microbiological Guidelines for Food" with "Microbiological Guidelines for Ready-to-eat Food (May 2007)" and the supplementary information to the Guidelines, what are the major changes?
Apart from textual amendments, major changes on the following aspects were made - (1) modifying the microbiological criteria in the Microbiological Guidelines for Ready-to-eat Food as well as establishing additional microbiological criteria with reference to international/ national standards and guidelines, (2) incorporating microbiological criteria stipulated in the supplementary information to the Guidelines, (3) revising the classification and nomenclature of microbiological quality and (4) putting in additional information on common foodborne pathogens in Appendix I of the Guidelines for reference. Since the Guidelines would include microbiological criteria for both ready-to-eat and non-ready-to-eat food e.g. powdered infant formula, the title of the Guidelines is also changed to "Microbiological Guidelines for Food".
It is noted that analytical methods are appended to some microbiological criteria in the Guidelines. Is it acceptable to adopt other analytical methods?
In the Guidelines, microbiological methods are appended to some microbiological criteria which are given in the relevant Codex standards and code of hygienic practices. Other equivalent methods that have been validated to provide appropriate sensitivity, reproducibility, reliability etc. could be employed. Preference should be given to methods which have been validated for the commodity concerned especially in relation to reference methods elaborated by international organisations. This is also applicable to other microbiological criteria in the Guidelines, which have no microbiological method appended.
How can I know the microbiological criteria for a specific food from the Guidelines?
The Microbiological Guidelines for Food include 3 chapters:
- Chapter I covers microbiological criteria for ready-to-eat food in general – aerobic colony count (ACC) and hygiene indicator organisms;
- Chapter II covers microbiological criteria for ready-to-eat food in general – specific foodborne pathogens
- Chapter III covers microbiological criteria for specific food items.
Chapters I, II and III should be read together for the microbiological criteria of a specified food. For example, for live and raw bivalve molluscs intended for direct consumption, the microbiological criteria of Escherichia coli and Salmonella spp. should be referred to those stipulated in Chapter III while other microbiological criteria should be referred to Chapters I and II.
However, it is noted that some microbiological criteria set out in Chapter III apply to certain food items which may not be ready-to-eat. It is therefore microbiological criteria stipulated in Chapters I and II would not be applied to these products.
Appendix II of the Guidelines has included the "Guidance notes on sampling plan for microbiological analysis". What are the purposes and factors to be considered during application?
The food trade may adopt a suitable sampling plan as shown in the "Guidance notes on sampling plan for microbiological analysis" to monitor the safety and quality of their food products.
Application of sampling plan is an effective way to monitor the microbiological quality of food products and the effectiveness of cleansing and disinfection procedures applied in food production plants. Before choosing a sampling plan, the trade should consider the following elements –
- Purpose of inspection
- Nature of product
- Nature of the sampling and analytical procedure
- Microbiological limits
- Resources availability
For details of the principle and application of the International Committee of Microbiological Specification for Foods' (ICMSF) sampling plan, please refer to the ICMSF publications - Microorganisms in Foods 2, Sampling for Microbiological Analysis: Principles and Specific Applications (2nd edition; 1986) and Microorganisms in Foods 7: Microbiological Testing in Food Safety Management (2002).
When is the effective date of the Microbiological Guidelines for Food?
The Guidelines are effective on 14 August 2014, except for the "Non-O157 Shiga toxin-producing E. coli " and "Enterobacteriaceae" criteria for ready-to-eat food in general which will be implemented when the testing capacity for these criteria are ready.
Microbiological Criteria for Ready-to-eat Food in General
What is ready-to-eat food?
"Ready-to-eat food" means food intended by the producer or the manufacturer for direct human consumption without the need for cooking or other processing effective to eliminate or reduce to an acceptable level the microorganisms of concern.
What are the components of microbiological criteria for ready-to-eat food in general?
The microbiological limits for ready-to-eat food in general consist of three components:
Aerobic colony count (ACC)
Aerobic colony count (ACC) is the total number of bacteria able to grow in an aerobic environment in moderate temperature. It is an indicator of quality, not safety, and cannot directly contribute towards a safety assessment of ready-to-eat food. In addition, ACCs can provide useful information about the general quality and remaining shelf life of the food in question, and thus highlight potential problems of storage and handling since production; however they are not deemed a priority in a risk based analysis.
Hygiene indicator organisms – E. coli and Enterobacteriaceae
E. coli is a commonly used faecal indicator organism. Its presence in food generally indicates direct or indirect faecal contamination. Substantial number of E. coli in food suggests a general lack of cleanliness in handling and improper storage.
Enterobacteriaceae is a large group of biochemically and genetically related bacteria used to assess the general hygiene status of a food product. Their presence in heat treated food indicates inadequate cooking or post-processing contamination. In addition, some members of Enterobacteriaceae can contribute to the formation of histamine (scombrotoxin) in foods such as scombroid fish and occasionally some cheeses if these are not processed properly and/or stored at an adequate refrigeration temperature.
Specific foodborne pathogens
Specific foodborne pathogens refer to bacteria that may cause food poisoning. Mechanisms involved may be toxins produced in food or intestinal infection. The symptoms of food poisoning vary from nausea and vomiting (e.g. caused by Staphylococcus aureus enterotoxin), through diarrhoea and dehydration (e.g. caused by Salmonella spp. and Campylobacter spp.) to severe conditions such as septicaemia, meningitis, paralysis and death (e.g. caused by invasive Listeria monocytogenes and in the rare cases of botulism caused by Clostridium botulinum toxin). The Guidelines stipulate the safety limits of ten major specific foodborne pathogens in ready-to-eat food by making reference to scientific information, expert advice and international practices.
The microbiological criteria for ACC and hygiene indicator organisms are covered in Chapter I while those for specific foodborne pathogens are included in Chapter II.
Why are the microbiological criteria for ACC and hygiene indicator organisms and specific foodborne pathogens in ready-to-eat food in general laid down in two individual chapters?
Separating microbiological criteria for ACC and hygiene indicator organisms in Chapter I and microbiological criteria for specific foodborne pathogens in Chapter II makes a clearer distinction that the former parameters reflect the quality but not safety of food, while the latter contribute to food safety.
What are the classifications of microbiological quality of ready-to-eat food in general?
The microbiological assessment of ready-to-eat food i.e. ACC, hygiene indicator organisms and specific foodborne pathogens, will lead to the classification of microbiological quality into one of the following three classes:
- Satisfactory : test results indicating good microbiological quality.
- Borderline : test results that are not unsatisfactory but are also not satisfactory, are on the upper limit of acceptability and which indicate the potential for development of public health problems and of unacceptable risk.
- Unsatisfactory : For ACC, test results which indicate investigating reasons for high count may be considered. For hygiene indicators, test results that require remedial action. For pathogens, test results at levels which indicate a product that is potentially injurious to health and/or unfit for human consumption and require immediate remedial action.
What are the corresponding follow-up actions to be taken by officers for each class i.e. satisfactory, borderline and unsatisfactory in response to ACC, hygiene indicator organisms and specific foodborne pathogens?
Hygiene indicator organisms
Specific foodborne pathogens
( NB: Perfo r m risk assessment before any further action )
No action required.
Consider the source of the food (producer/ retailer etc.) and the stage of shelf life before determining action. If other samples from the same source are also of borderline quality, further investigation may be appropriate.
Parties concerned (e.g. vendors) should be advised to review cooking and all hygiene procedures including cleaning. Consider taking investigative food samples. Action should be proportional to the levels detected.
Risk will increase proportional to the levels detected. Parties concerned (e.g. vendors) should be advised to investigate and find out the causes and to adopt measures to improve the situation. Consider taking investigative food samples.
Consider investigating reasons for high count.
Parties concerned (e.g. vendors) should be advised to review cooking and all hygiene procedures including cleaning. Take investigative food samples.
Immediate investigation; Parties concerned (e.g. vendors) should be instructed to stop sale of food item in question, investigate immediately and find out the causes and to adopt measures to improve the situation. Take investigative food samples. In addition, warning letters, source tracing and other enforcement actions should be considered.
How can I classify a ready-to-eat food into one of the 14 food categories for ACC assessment?
In order to classify a ready-to-eat food into one of the 14 food categories for ACC assessment, you have to make reference to the raw ingredients used, the nature and degree of processing of the ready-to-eat food. Typical food examples in each food category are provided for reference. For food items that are not included in these food categories, their ACC level should be interpreted taking into account the raw ingredients used, and the nature and degree of processing before sale. Due to the diversity of food products and their respective processing, a good understanding of the product type is needed in order to fully interpret the ACC results.
What are the references of the ACC limits for different food categories?
The main reference of the ACC limits for different food categories is the "Guidelines for Assessing the Microbiological Safety of Ready-to-eat Foods Placed on the Market" published by the Health Protection Agency in the United Kingdom while taking local food categories and surveillance data into account.
It is noted that different ACC limits are applied to different food categories. Are there any differences regarding the limits of hygiene indicator organisms and specific foodborne pathogens in different food categories?
No. The microbiological criteria for hygiene indicator organisms and specific foodborne pathogens apply to all ready-to-eat food in general unless otherwise specified.
A footnote "this criterion applied to all refrigerated food (excluding frozen food) unless there is scientific evidence supporting that the food concerned does not support the growth of Listeria monocytogenes under refrigeration" is marked on the Listeria monocytogenes criterion for refrigerated food. How can I know if an individual ready-to-eat food supports the growth of Listeria monocytogenes under refrigeration or not?
According to the Codex Guidelines on the Application of General Principles of Food Hygiene to the Control of Listeria monocytogenes in Food (CAC/GL 61-2007), ready-to-eat foods in which growth of Listeria monocytogenes will not occur would be determined based on scientific justification, including the inherent variability of factors controlling Listeria monocytogenes in the product. Factors such as pH, a w , are useful in preventing growth. For example, Listeria monocytogenes growth can be controlled in foods that have:
- a pH below 4.4,
- an a w < 0.92,
- a combination of factors (pH, a w ,), e.g. the combination of pH < 5.0 with a w < 0.94.
Such growth can also be controlled by freezing (during that period when the product remains frozen).
In addition, the growth of Listeria monocytogenes can also be controlled in ready-to-eat foods which contain certain preservatives such as potassium lactate, sodium acetate, sodium diacetate, sodium lactate.
Should you have any doubt on whether a ready-to-eat food can support the growth of Listeria monocytogenes , please seek professional advice from the food scientists. If information is lacking to demonstrate that a ready-to-eat food will not support the growth of Listeria monocytogenes during its expected shelf life, conservative approach should be taken; the food would be regarded as possible supportive of growth.
Microbiological Criteria for Specific Food Items
How can I interpret the microbiological results for specific food items listed under Chapter III?
Any food samples failing any of the microbiological criteria stipulated in Chapter III will be considered as "Unsatisfactory: Potentially injurious to health and/or unfit for human consumption". In other words, the affected products should be prevented from being released for human consumption.
It is noted that different microbiological criteria are established for " ice from ice manufacturing plants and packaged ice from retail outlets" and " loose ice from retail outlets " . Why?
The Guidelines has laid down more stringent requirements for ice from manufacturing plants and packaged ice from retail outlets than loose ice from retail outlets in terms of total coliform bacteria and ACC. One of the reasons is that packaged ice is less likely to expose to environmental contamination in an intact package, while for loose ice from retail outlets (including those produced on premises or supplied by ice manufacturing plants and unpacked by the premises) which may have undergone some handling processes and may expose to airborne and environmental contamination.
What are non-bottled drinks?
Generally speaking, non-bottled drinks are those drinks prepared for immediate consumption and do not require storage in sealed bottles, cans or other containers, for example, fresh fruit juice, diluted drinks prepared from concentrated fruit juice or syrup, soya bean juice, etc. Drinks sold from a manual dispensing machine also belong to this category.
What are the microbiological criteria for ready-to-feed liquid formulae for infants and young children?
Ready-to-feed liquid formulae for infants and young children shall be a commercially sterile product.
Can you name some bivalve molluscs examples?
Bivalve molluscs include clams, cockles, mussels, oysters and scallops.
It is noted that an E. coli criterion has been stipulated for live or raw bivalve molluscs intended for direct consumption. Does E. coli indicate the presence of viruses in these products?
E. coli is used as an indicator for the presence of faecal contamination. However, it does not correlate well with the presence of viruses in these products.
Is there any norovirus criterion for live or raw bivalve molluscs intended for direct consumption stipulated in the Guidelines?
No. It is because currently there is no threshold infectivity limit for norovirus and the number of genome copies detected by quantitative polymerase chain reaction may not relate to infectious norovirus.
Nevertheless, the trade should pay special attention to the hygienic and safety conditions of the live or raw bivalve molluscs intended for direct consumption and ensure they were fit for consumption.
Can you name some spices examples?
According to the Codex Classification of Foods and Animal Feeds, spices consist of the aromatic seeds, roots, berries or other fruits from a variety of plants, which are used in relatively small quantities to flavor foods. Examples of spices include coriander seed, fenugreek seed, poppy seed, black and white pepper, nutmeg, sesame seed etc which are treated to be consumed primarily as condiment.
Centre for Food Safety
Food and Environmental Hygiene Department