Food Surveillance Australia New Zealand
Autumn/Winter 2005 edition
Full colour version [ pdf 325 kb ]
Contents
Editorial– by Martyn Kirk (OzFoodNet) & David Jordan (NSWDPI )
Sushi and Asian meat temperature control research
Victorian Food Safety News - Have you read this publicationMicrobiological Survey – Sesame Seeds and Sesame Seed Products
Dioxins in Food – Dietary Exposure Assessment and Risk Characterisation
Hand washing – we don’t always do the right thing
Western Australian Food Monitoring Program – Micro Quality of Cooked Chicken Meat 2003-2004
AQIS Imported Food Inspection Scheme – 3rd & 4th quarter 2003 results
Editorial - Surveillance of food hazards in Australia
 Martyn Kirk |
David Jordan |
The World Health Organization and many countries around the world have recognised that monitoring contamination of foods is a key part of strong food safety infrastructure.1 Traditionally the contaminants that caused most concern to food safety agencies were microorganisms, pesticide residues, and chemical contaminants, but the focus has now broadened to include genetically modified foods, food labelling and allergens.
Food surveillance has been defined as ‘the continuous monitoring of the food supply to ensure consumers are not exposed to components in foods, such as chemical contaminants or biological hazards’.1 Surveys that are regularly repeated to monitor long term trends of contaminants can be considered surveillance. In contrast to surveillance of human disease that considers morbidity and mortality, food surveillance monitors the occurrence of ‘hazards’ in the food supply.2 In public health, there is a need to make sure that data arising from surveillance activities are provided to people who are in a position to act (see the World Bank Surveillance Toolkit http://survtoolkit.worldbank.org/ ). When it comes to surveillance of the food supply, this may mean people who manage and communicate about risks and other public health staff, including local council officers, disease control agencies, other government departments, industry and advisors to industry.
Food surveillance is complicated by the fact that the types of tests on foods are often not standardised between laboratories or jurisdictions, and the methods often vary from survey-to-survey. It is important that food surveys have clearly defined objectives and a well-planned method of collecting and analysing samples.3 One of the most critical issues for conducting good surveys is the issue of sampling. The number of samples required for a survey depends on the expected rate of contamination of the food, the desired accuracy of the prevalence estimate, the distribution of that contamination (whether it is randomly dispersed throughout product items or strongly clustered through time, space or both) and the need to compare results between foods, geographic areas, times, seasons and other factors. For such comparisons to be valid it is imperative that probabilistic sampling methods are used as much as possible (these include simple random sampling, stratified random sampling and so on).4
The performance characteristics of the test can have a critical influence on the robustness of survey results and their interpretation. Stuttard et al. give an example that the probability of detecting Salmonella from ten replicated tests of a batch of desiccated coconut that is 1% contaminated is only 9.6%.3 In many food surveys only single samples are ever collected from a batch making the probability of detecting contamination very small. Even when multiple samples are collected from a batch, the probability of correctly classifying the contamination status of that batch is not necessarily high. This sampling issue is known as ‘herd testing’ and has been reviewed in detail in the veterinary literature.5 It is hoped that in the future a greater proportion of surveys for hazards in food can be based on tests and sampling procedures for which the performance characteristics have been objectively assessed. Such knowledge can be vital to agencies that conduct these surveys because it allows them to consider what action they will take if they find food that is contaminated and what assurances they provide in the case of negative tests.
The use of food survey data is becoming increasingly important in the development of risk assessments and risk management strategies. Survey data are vital to assess the likely exposure from consumption of food commodities.6 Surveying the safety of foods during growing, harvesting, processing and transport is also important for identifying the best place to intervene and reduce human disease. A good example of repeated surveys for hazards in foods are the retail studies performed by the Australian Capital Territory Health Department which include a wide range of foods, including ‘ready-to-eat’ items, seafood, chicken meat, and most recently fried rice and sushi (see: http://health.act.gov.au/c/health?a=da&did=10060655 ).
These surveys are very important because they objectively quantify the probability of consumers being exposed to hazards. In the ACT survey of the microbiological quality of sushi only 63% of samples had a pH lower than 4.8. This relates directly to the results of Victorian Department of Human Services research into temperature control of sushi summarised in this issue of Food Surveillance Australia New Zealand. The Victorian research recommended that nigiri sushi may be held at temperatures up to 15 Celsius for up to 8 hours if the pH is lower than 4.8. The high proportion of sushi in the ACT survey that did not meet this pH requirement is a concern for consumers.
This example emphasises that surveillance need not be confined to making measurements on ‘hazards’. Measurement of food attributes (e.g. pH), processing attributes (e.g. temperature) and storage attributes (e.g. storage time) can be very useful when these are known determinants of product safety and food-borne disease. Sushi has recently been implicated in outbreaks of Salmonella and enterotoxigenic E. coli infection, which highlight the need to educate proprietors about proper preparation of sushi.7, 8
Surveillance of foods, along with the findings of investigations of foodborne disease outbreaks, are important to identify areas for intervention and make the food supply safer.9 A national survey of sesame seed products reported in this issue of Food Surveillance Australia New Zealand was initiated following outbreaks of salmonellosis from imported tahini and halva.10 The survey found that the level of contamination of sesame seeds was quite low, although one sample of white sesame seeds was positive for Salmonella Richmond. As a result of these outbreaks and positive samples, the testing frequency of sesame seed products imported into Australia was increased.
In recent years, there has been an increasing recognition of imported foods as a source of foodborne disease.10 Surveillance of imported foods is important to safeguard the food supply and failures can indicate high risk foods requiring more intensive surveillance.11 The reasons for testing failure of foods imported into Australia for the last two quarters of 2003 are documented in this issue of the newsletter. The data collection system for imported food testing is currently being revised. It will be important to see regular results of monitoring imported foods in future issues of this newsletter.
This issue of Food Surveillance Australia New Zealand also summarises a Western Australian survey showing that cooked chicken products are commonly contaminated with Listeria monocytogenes. L. monocytogenes infections may result in meningitis or septicaemia in neonates or people who are immunocompromised. There are approximately 60 cases of listeriosis in Australia each year, making it a rare form of foodborne disease.10 However, listeriosis is a severe health condition and 20% of reported infections in immunocompromised individuals are fatal. The Western Australian survey found that 41% of chicken samples were contaminated with L. monocytogenes, which justifies the public health advice for pregnant women and immunocompromised people to avoid eating chicken products that may have been held at temperatures allowing Listeria to grow, including commercially cooked chicken.
Each Australian jurisdiction conducts numerous surveys into potential food safety issues each year. Without coordination and sharing of information there is a significant possibility of duplicating surveys. The Food Regulation Standing Committee’s Implementation Sub-Committee has a working group to coordinate survey activity across Australia to avoid the likelihood of duplication. The working group documents current and future surveys so jurisdictions can see what surveys are planned, and allows multiple jurisdictions to join together and participate in single surveys. The survey of sesame seed products in this issue is an example of a coordinated national survey of food. Food Surveillance Australia New Zealand has an important role in sharing the information that Australian jurisdictions collect on the quality of foods supplied to consumers.
Hopefully in the future, food safety agencies will conduct joint surveys that run over successive years to allow monitoring of interventions.12 At the moment, Food Standards Australia New Zealand is developing new food standards that extend to the primary production settings of farms and processing environments. Standards that are currently in development include those covering seafood, poultry meat and dairy products. National surveys of these commodities that are repeated regularly will be important for Australia to monitor the effect of these interventions in years to come.
References
- World Health Organization, Food & Agriculture Organization. Assuring Food Safety & Quality, Guidelines for strengthening national food control systems. Geneva, 2004. Available at: http://www.who.int/foodsafety/publications/capacity/en/Englsih_Guidelines_Food_control.pdf Accessed on 30 March 2005.
- Thacker SB, Stroup DF, Parrish RG, Anderson HA. Surveillance in environmental public health: Issues, systems, and sources.Am J Public Health .1996;86: 633–8. WHO/SDE/PHE/FOS/01.4.
- Stuttard E, Eglezos S, Jenson I. Sampling for Microbiological Analysis. In: Foodborne Microorganisms of Public Health Significance. Ed. Hocking AD, AIFST Inc., Sydney, 2003.
- Levey PS, Lemeshow S. Sampling of Populations, 3rd edn, John Wiley and Sons, New York, 1999.
- Christensen J, Gardner IA. Herd-level interpretation of test results for epidemiologic studies of animal diseases.Prev Vet Med2000,45: 83-106.
- World Health Organization. Joint FAO/WHO Expert Consultation on Risk Assessment of Microbiological Hazards in Foods Hazard identification, exposure assessment and hazard characterization of Campylobacters pp. in broiler chickens and Vibrios pp. in seafood. Geneva, Switzerland 2001, WHO/SDE/PHE/FOS/01.4
- Barralet J, Stafford RJ, Towner C, Smith P. Outbreak of Salmonella Singapore associated with eating sushi.Comm Dis Intell 2005; 28: 527–8.
- Anon. WASHOE COUNTY DISTRICT HEALTH DEPARTMENT INVESTIGATES OUTBREAK OF GASTROINTESTINAL ILLNESS. Washoe County Press Release. Available at:http://www.co.washoe.nv.us/health/pr/2005/January/sp2.html~color=grey&text_version = Accessed on 30 March 2005.
- O'Brien SJ, Elson R, Gillespie IA, Adak GK, Cowden JM. Surveillance of foodborne outbreaks of infectious intestinal disease in England and Wales 1992-1999: contributing to evidence-based food policy? Public Health. 2002;116:75–80.
- The OzFoodNet Working Group. Foodborne disease investigation across Australia: annual report of the OzFoodNet network, 2003.Commun Dis Intell. 2004;28:359-89.
- Bull AL, Crerar SK, Beers MY. Australia's Imported Food Program—A valuable source of information on micro-organisms in foods.Commun Dis Intell2002; 26: 28–32.
- Kirk M. Foodborne surveillance needs in Australia: harmonisation of molecular laboratory testing and sharing data from human, animal, and food sources.N S W Public Health Bull 2004;15:13–7.
Sushi and Asian meat temperature control research
The Department of Human Services Food Safety Unit in Victoria has been aware of the increasing diversity of Victoria’s ethnic population and their involvement in food retail and service businesses. This has resulted in the availability of a wide variety of cuisine. Some of these foods, when prepared traditionally, could have their quality and flavour compromised if they complied with the strict temperature requirements of the Food Safety Standards.
The Food Safety Unit in Victoria conducted research in 2003-04 on the following traditional foods:
Sushi products
- Nigiri pieces and Nori Rolls
Asian meats
- Chinese style Roast Duck (‘Peking Duck’),
- Chinese Style Chicken and
- Chinese Style Roast and Barbequed Pork.
Scientific validation was sought on the safety of these products - under alternative temperature control arrangements (within the temperature danger zone of 5 ºC – 60 ºC).
Research and microbiological testing found that with a pH of 4.8 or less the Sushi products, Nigiri pieces and Nori Rolls, can be kept at 15 ºC or less for a period of up to, eight or twelve hours, respectively.
Similar testing of the Asian meats found that, if prepared and handled in specific ways, they can be left on display at ambient temperatures. Chinese Style Duck and Chicken can be left on display for up to twenty-two hours, with internal temperature of no more than 25 ºC, while Chinese Style Roast and Barbeque Pork can be on display for up to seven hours.
As a result of this research, the Food Safety Unit has developed and adopted two additional supplements for the existing Food Safety Program templates. They are:
- Supplement B – Sushi, and
- Supplement C – Chinese style products.
Both Supplements B & C are optional and businesses can choose to use them or adhere to the current requirements under the Food Safety Standard. The development of these supplements recognises the benefits of traditional food preparation and storage. The use of these new templates allows food businesses to display and keep certain foods out of the standard temperature control range.
| The Food Safety Standards require all potentially hazardous food to be handled and displayed under temperature control - cold foods at 5ºC or less and - hot foods at 60ºC or greater. The interpretation guidelines to the Standards, however, permit these foods to be out of temperature control for up to 4 hours. Any greater time than this requires scientific validation The Victorian Food Act requires that all Victorian food businesses must have lodged a Food Safety Program with their Local Council after 1 February 2002 upon registering or re-registering The Food Safety Unit have developed templates to assist food businesses in developing their own Food Safety Programs A Food Safety Program is a written plan that shows what a food business is doing to manage the safety of the food they prepare, serve, manufacture and sell. Access the templates and further information through the website http://www.health.vic.gov.au/foodsafety/ or by contact the Food Safety Unit on 1300 364 352. |
For Further Information
Read the full report, Foods kept under alternative temperature control: Sushi products – Nigiri pieces and Nori Rolls; Asian meats – Chinese style Roast Duck (‘Pecking Duck’), Chinese Style Chicken and Chinese Style Roast and Barbequed Porks), using the following link: www.health.vic.gov.au/foodsafety/research/microbiological or contact Food Safety Officer Violette Lazanas of the Food Safety Unit with the Victorian Department of Human Services, on (03) 9637 4086
Victorian Food Safety News – Have you read this new publication?
In June 2004 the Department of Human Services Food Safety Unit in Victoria introduced a news journal for the food and food safety industry. Victorian Food Safety News will highlight developments, projects, initiatives and best practice examples in food safety. It also attempts to raise the profile and strategic importance of food safety. Volume 1 includes articles on kebabs, freshly squeezed juices, meat pies and food safety and can be read by accessing the following link:http://www.health.vic.gov.au/foodsafety/downloads/foodsafety_news_winter04.pdf
Volume 2 is also available by accessing:-http://www.health.vic.gov.au/foodsafety/downloads/foodsafety_news_autumn05.pdf
Dioxins in Food – Dietary Exposure Assessment and Risk Characterisation.
The term ‘dioxins’ refers to a group of chlorinated chemicals that are chemically stable and can remain in the environment for a long time. Dioxins include the polychlorinated dibenzodioxins (PCDDs or dioxins), the closely related polychlorinated dibenzofurans (PCDFs or furans) and certain polychlorinated biphenyls (dioxin-like PCBs, or PCBs). Dioxins enter the food chain when animals eat contaminated plants. The dioxins are then absorbed into the animal fat, increasing in concentration as they migrate up the food chain. The consumption of animal products with high fat content, such as meat and dairy products, can increase human exposure to dioxins.
As part of the National Dioxins Program, an Australian Government funded initiative implemented by the Department of the Environment and Heritage, Food Standards Australia New Zealand (FSANZ) examined dioxin levels in a range of foods to determine the level of dioxin exposure of Australians through food and to assess the human health risk. This assessment contributed to the human health risk assessment undertaken by the Department of Health and Ageing that considered the overall impact of dioxins from all sources on human health.
Dioxin dietary exposure is determined by examining dioxin levels in various foods and combining this with information on the daily diet of the population. Foods likely to contain dioxins are those that contain animal fats, such as dairy products, meat and meat products, fish and eggs.
Dioxin levels in food were determined by analysis of 168 samples of 22 randomly sampled foods from Australian retail outlets which were prepared ready to eat. The mean range of dioxin concentrations found in the foods analysed are set out below. The survey found that Australian foods have low levels of dioxins - similar to those reported in New Zealand and lower than the levels found in some European and north American surveys.
Mean range of dioxin concentrations in food, in pg TEQ/g fresh weight
Food | Concentration range | Food | Concentration range |
Bacon | 0.025-0.083 | Leg ham | 0.0016-0.017 |
Baked beans | 0.0012-0.016 | Liver pate | 0.0025-0.043 |
Bread, white | 0.00067-0.026 | Margarine | 0.0025-0.058 |
Butter | 0.028-0.27 | Milk chocolate | 0.0077-0.056 |
Chicken breast | 0.0044-0.021 | Milk, whole | 0.0023-0.012 |
Eggs | 0.0088-0.057 | Minced beef | 0.0054-0.048 |
Fish fillets | 0.59-0.64 | Orange juice | 0.00018-0.007 |
Fish portions | 0.019-0.039 | Peanut butter | 0.035-0.25 |
Hamburger | 0.00050-0.027 | Potatoes | 0.00029-0.014 |
Infant formula | 0.0036-0.018 | Sausage | 0.0096-0.058 |
Lamb chops | 0.0044-0.045 | Tuna, canned | 0.029-0.041 |
These results were then combined with dietary information from the 1995 National Nutrition Survey to assess the population’s dietary exposure As shown in the figure below, for all age groups from two years and over, the estimated monthly dietary levels of exposure to dioxins, for both the average and high consumer, were well below the Australian Tolerable Monthly Intake of 70 pg TEQ/kg body weight/month .
Because of their high dietary intake relative to body weight, highest mean intakes for all age groups occur in infants and toddlers. In general terms, the estimated monthly level of exposure to dioxins for Australians (3.7-15.6 pg TEQ/kg body weight/month, lower to upper range) is similar to that of New Zealand (11.1 pg TEQ/kg body weight/month, middle value for adult males) and lower than that of other industrialised nations for which survey data were available. For example in the United Kingdom, the estimated exposure to dioxins for the population was 15-21 pg TEQ/kg bw/month.
Mean range of exposures to dioxins for each population group in Australia, as a percentage of the Tolerable Monthly Intake.
The major foods contributing to dioxin exposure for the Australian population over a lifetime were fish (including crustaceans and molluscs), milk and dairy products. For toddlers and children, the major foods contributing to dioxins exposure were milk and dairy products.
As there are limitations associated with the data used to characterise the risk associated with exposure to dioxins from food, in general, conservative assumptions were used to minimise the possibility that risks would be underestimated. On the basis of this analysis the public health and safety risk for all Australians from exposure to dioxins from foods is very low.
A copy of the full FSANZ report and associated information on dioxins in food is available on the FSANZ web site at: http://www.foodstandards.gov.au/whatsinfood/dioxinsinfood.cfm.
Further information on the National Dioxin Program is available from the Department of the Environment and Heritage at: http://www.deh.gov.au/industry/chemicals/dioxins/index.html .
Microbiological Survey - Sesame Seeds and Sesame Seed Products
Background
In Australia and overseas, sesame seeds and sesame seed products (tahini, halva, hummus and baba ghanouj) have been linked with outbreaks of foodborne illness, mainly due to contamination with Salmonella. Most of the products implicated in recalls and foodborne illness in Australia were produced in Middle Eastern countries. Domestic testing of sesame products over the last 20 years has resulted in the detection of salmonellae on numerous occasions. However, testing of imported halva by the Australian Quarantine Inspections Service (AQIS) for three months in 2001 did not result in the detection of Salmonella, and testing of imported tahini for a number of months in 2003 only resulted in one Salmonella detection out of 39 samples (AQIS unpublished data, 2003). Over the same period in 2003, Salmonella was detected in imported halva and tahini available on the domestic market. Therefore, AQIS test results suggest that Salmonella contamination of sesame seed products may occur at very low levels, or is sporadic and as such is not routinely picked up by imported food tests.
In most outbreak and recall cases in Australia, Salmonella contamination in implicated sesame seed products appears to have occurred prior to importation. However, the potential for Salmonella contamination of these products within Australia cannot be fully ignored. The survival of Salmonella in contaminated products is aided, especially in tahini, by a very long shelf life. Salmonella survives for some time in tahini and products made using tahini as an ingredient may in turn be contaminated. As these products are often not cooked, any pathogens present may not be subjected to a kill step . In addition, amplification of Salmonella numbers can occur because the manufactured product often has a higher water activity than that of tahini, thus allowing for growth of Salmonella.
Aim of Survey
The aim of the survey was to provide further information on Salmonella contamination of domestically produced and imported sesame seed products available on the Australian market, and was intended to supplement the testing of imported products at the border. The survey was not intended to be comprehensive but rather to provide a ‘snapshot’ as to whether there are contaminated products on the Australia market. The survey also helped inform whether the current imported food testing regime is adequate in testing for Salmonella in terms of the number of samples taken per batch and the sensitivity of the analytical method.
Survey Method
This survey was coordinated by FSANZ in conjunction with interested State and Territory jurisdictions.
Victorian, Tasmanian, Queensland, South Australian and New South Wales health agencies collected samples during the first two weeks in May 2004. A total of 40 samples, approximately half domestic and half imported, were collected and tested. To investigate whether the current food sampling regime was sufficiently sensitive, 5 sub-samples of product within the same lot code (minimum weight of 25 g) were taken for each sample.
Types of sesame seed products sampled included sesame seeds, tahini, halva, hummus and baba ghanouj. Canned products were not sampled, as they were likely to be sterile. Samples were selected from a range of outlets including wholesalers, supermarkets, fast-food outlets/restaurants and grocers/delis. Product details were recorded to allow trace-back, if necessary.
The temperature of refrigerated samples was taken at the time of purchase. To avoid microbial growth samples were transported to the analytical laboratory at 0-4 ° C.
Analysis
The Microbiological Diagnostic Unit Public Health Laboratory at the University of Melbourne conducted sample preparation and analysis.
Samples were analysed using the method i