Food Surveillance Australia New Zealand
Spring 2003 edition
[ Full colour version pdf 268 kb ]
In this issue...
Survey of Listeria monocytogenes in cooked prawns
When is organic food not organic?
Weekend Produce Markets around Adelaide - A Survey of Horticultural Produce for Chemical Residues
Quantitative Consumer Research on Labelling Issues
AQIS Imported Food Inspection Scheme - 1st quarter 2003 results.
Editorial
Like the variety and complexity of surveillance and enforcement work undertaken by Public Health Units all around Australia and New Zealand, this edition is a mixed bag of both 'snapshots' and in-depth surveillance. It reports on some microbiological and chemical residues studies and also introduces a new segment where quarterly results from the AQIS Imported Food Inspection Scheme are reported.
This edition contains a number of long-term projects that have been undertaken by FSANZ that have either just been released or are soon to be released: a report on the results of a survey of Listeria monocytogenes in cooked prawns, when is organic food not organic?; the report 'Food Labelling Issues : Quantitative Research with Consumers' and the finalisation and publication of a technical paper on chloropropanols in food .
Survey of Listeria monocytogenes in cooked prawns #
Introduction
In 2002, Food Standards Australia New Zealand (FSANZ) coordinated a microbiological survey of cooked prawns. The objectives of the survey were:
- to determine the frequency and level of Listeria monocytogenes contamination in both domestically produced and imported cooked prawns at retail; and
- to measure the standard plate count (SPC) in cooked prawns at retail (i.e. at the point of sale) as a possible indicator of shelf life.
Based on FSANZ's review of the microbiological standard for Listeria monocytogenes in cooked prawns, it was considered that further data on the prevalence of Listeria monocytogenes in cooked crustacea were needed to assess the risk posed from the consumption of cooked crustacea. Data from the survey were used in probabilistic modelling as part of FSANZ's 'Microbiological Risk Assessment:Listeria monocytogenes in Cooked Crustacea' (FSANZ, 2002).
Methods
A total of 380 samples of unpackaged Australian and imported cooked prawns were collected from Brisbane, Melbourne, Sydney and Perth. A range of prawns including peeled and unpeeled, were sampled as shown in Table 1. Additional information was recorded for each sample at the time of purchase, which included the temperature of the samples.
Table 1. Breakdown of prawns by frequency and type
Type of prawn | ||||||||
Peeled | Unpeeled | Imported | Domestic | Frozen | Chilled | Supermarket | Seafood retailer/fish market | |
No. of Samples | 89 | 290 | 139 | 230 | 67 | 313 | 195 | 185 |
Total | 379 | 369 | 380 | 380 | ||||
Microbiological analyses were conducted by the Australian Government Analytical Laboratory (AGAL) and the Western Australia Centre for Pathology and Medical Research.
All cooked prawns were analysed for Listeria monocytogenes and SPC using standard methods. The enumeration of Listeria monocytogenes was conducted in tandem with the presence/absence test for Listeria monocytogenes. The limit of detection for enumerating Listeria monocytogenes was 50 colony forming units per gram (cfu/g). A dilution range of 10-3 - 10-5 was used to determine the standard plate count SPC for each sample (sub-sample). This gave a minimum detection range of 104 - 107 cfu/g.
Results
Temperature
Cooked prawns were sampled either as 'frozen' or 'chilled' under retail conditions.
The average temperatures recorded for chilled cooked prawn samples at retail varied from -5.5oC to 12.8oC. The majority (59%) of chilled samples had average temperatures between 0oC and 5oC (Figure 1). 113 chilled samples (36%) had average temperatures exceeding 5oC. There was no apparent difference between the temperatures of cooked prawns sampled from supermarkets compared to the temperatures of cooked prawns sampled at fish market/specialist fish retailers.
Figure 1: Average Temperature of Cooked Prawn Samples at Retail (excluding samples recorded as 'frozen')
Standard Plate Count
Standard plate counts were undertaken to determine levels of microbiological contamination. The SPCs ranged from less than 103 to greater than 107 cfu/g. Figure 2 shows the range of SPCs obtained for both frozen and chilled cooked prawns.
Frozen cooked prawns generally had lower SPCs than chilled product and there was no apparent association between high SPCs and whether the prawns were peeled or unpeeled, imported or domestic, or the different types of retail outlets. There was also no apparent association between the high SPCs and higher temperatures recorded at retail.
Although the best-before date was recorded when available, there was insufficient information to associate the high SPCs with best-before dates.
Figure 2: Frequency histogram showing the range of mean SPC for cooked prawns
.
Listeria monocytogenes
The 380 samples were tested for Listeria monocytogenes and twelve (3%) were found to be positive. There were no counts of Listeria monocytogenes greater than 50cfu/g. Table 2 provides a breakdown of the total number of samples positive for Listeria monocytogenes according to origin (imported or domestic product) and type (peeled or unpeeled).
Table 2: Comparison Between Number of Samples Positive for Listeria monocytogenes and the Total Number of Samples
Type of Prawn | Total No. | |||
Imported | Domestic | Unknown | ||
Peeled | 6/77(8%) | 0/8 | 1/4 | 7/89(8%) |
Unpeeled | 1/62(2%) | 4/221 (2%) | 0/7 | 5/290(2%) |
Unknown |
| 0/1 |
| 0/1 |
Total | 7/139 (5%) | 4/230(2%) | 1/11(9%) | 12/380(3.2%) |
Peeled prawns had a higher contamination rate than unpeeled prawns (8% and 2% respectively). This difference was statistically significant (Fishers Exact Test, p=0.009).
Contamination rates for unpeeled prawns were similar for both imported and domestic products. Imported prawns had a higher contamination rate than domestic prawns but this result was not statistically significant.
Discussion and Conclusions:
Results from this survey indicate that the contamination rate of cooked prawns in Australia with Listeria monocytogenes is low (3%) and are comparable with surveys published in the international literature where rates are frequently below 10% for retail samples (Adesiyun, 1993; Gecan et al, 1994; Hartemink et al, 1991; Hofer et al, 1990; McLauchlin and Nichols, 1994). As a comparison Listeria monocytogenes contamination rates reported in smoked salmon are generally much higher and range from 10 to 20% at retail, with contamination rates of up to 40% recorded (FSANZ, 2002).
The data from the survey were used in probabilistic modelling to assess the risk posed from the consumption of cooked crustacea contaminated with Listeria monocytogenes. The FSANZ 'Microbiological Risk Assessment:Listeria monocytogenesin Cooked Crustacea' concluded that Listeria monocytogenes in cooked crustacea poses a low risk to the Australian population (FSANZ, 2002). However, the significant difference reported in this survey between contamination rates of cooked peeled and unpeeled prawns (8% and 2%) indicates that there may be a higher exposure to individuals consuming cooked peeled product versus other forms of crustacea to Listeria monocytogenes.
Standard 1.6.1 - Microbiological Limits for Food - of the Australia New Zealand Food Standards Code(the Code) requires cooked crustacea to have a SPC below 106 cfu/g. All of the cooked prawns sampled as 'frozen' had average SPCs less than 106 cfu/g and met the requirements of the Code. 19% of chilled cooked prawn samples had average SPCs greater than 106 and exceeded the limit set in the Code. High SPCs can be indicative of poor process control or may result from inadequate cooking and/or cross-contamination, and/or inappropriate temperature control during storage and display. In addition the high SPCs could also have indicated the prawns to be near the end of or past their shelf-life.
Standard 3.2.2 - Food Safety Practices and General Requirements - of the Code requires food businesses to store potentially hazardous foods under temperature control, which is defined as maintaining food at a temperature of 5oC or below. The majority (64%) of cooked prawn samples (excluding 'frozen' product) met the temperature control requirements of Standard 3.2.2. The samples (36%) with recorded temperatures above 5oC clearly did not meet temperature controls and indicated that a number of retail outlets need to improve temperature control for these products.
# The information in this article was presented as a poster to the 11th Australian Institute of Food Science and Technology Food Microbiology Conference, Noosa (March 2003) and was prepared by
Narelle Marro, Sally Hasell*, Julie Boorman, Scott Crerar
Food Standards Australia New Zealand, Canberra, Australia
* New Zealand Milk, Wellington, New Zealand
References
ANZFA (1999) P178 ¨C Review of Microbiological Standards ¨C Full Assessment Report, ANZFA, Canberra
Adesiyun (1993) Prevalence of Listeria spp.,Campylobacter spp.Salmonella spp.Yersinia spp. and toxigenic Escherichia coli on meat and seafoods in Trinidad, Food Microbiology, 10, 395 - 403
FSANZ (2002) Final Assessment Report, Proposal P239, Listeria -risk assessment and risk management strategy, FSANZ, Canberra
Gecan J, Bandler R and Staruszkiewicz W (1994) Fresh and frozen shrimp: a profile of filth, microbiological contamination, and decomposition, Journal of Food Protection, 57 (2) 154 - 158
Hartemink R and Georgsson F (1991) Incidence of Listeria species in seafood and seafood salads, International Journal of Food Microbiology, 12, 189 - 196
Hofer E and Ribeiro R (1990) Ocorrencia de especies de Listeria em camarao industrializado, Revista de microbiologia, 21 (2), 207 ¨C 208
McLauchlin J and Nichols G (1994) Listeria and seafood, PHLS Microbiology Digest, 11 (3), 151 - 154
For more information contact: Dr Scott Crerar, phone: 02 6271 2235, email: scott.crerar@foodstandards.gov.au
When is organic food not organic?
The organic food industry is a small market industry, which has a growth rate exceeding 20% per annum in Australia. There is evidence to suggest that more people are consuming organic foods as an alternative from traditionally processed foods. Because of the increased popularity of the organic market and the rapid increase in market growth, the Food Surveillance Advisory Committee (Queensland Health) commissioned a survey to sample food represented as ‘organic’ so as to increase the understanding of the organic food industry.
The organic certification process was reviewed and information regarding the processes of the industry and regulatory services was gathered. 96 samples of foods represented as ‘organic’ were sampled for analysis.
All samples were forwarded to Queensland Health Scientific Services where they were analysed for a broad screen of organochlorine, organophosphorus and synthetic pyrethroid pesticides.
Analysis results were as follows:
- Pesticide residues were found in 14 (14.6%) of samples represented as ‘organic’. Of these samples about 78% of these products were certified ‘organic’ (certified in country of origin).
- One product (Toasted Sesame Oil, manufactured in USA) contained a residue level that was the same as the maximum residue limit (MRL) stated in the Food Standards Code. All other residues found were below the stated MRL.
- Six (6.25%) of the products analysed contained residues that have no MRL in the Food Standards Code and therefore should not be detected in any foods.
Consumers may believe that food labelled, represented or sold as ‘organic’ or described by words of similar meaning will be ‘free’ of pesticides. The Food Standards Code does not include any specific labelling requirements or restrictions for foods advertised as ‘organic’. However, based upon typical consumers’ expectations, legal opinion may provide that the sale of food represented as ‘organic’ and which contained pesticide residues may be a breach of theFood Act, 1981.
The recommendations of the survey were that:
- further surveys should be conducted on foods represented as ‘organic’ to continue to monitor the levels of pesticide residues found in these foods; and
- future surveys should include the sampling of foods where data exists on the residues found in conventional food. This will allow comparisons to be made regarding the levels of pesticide residues on ‘organic’ vs. conventional foods.
Sharon Jurd
Director Environmental Health Services,
Gold Coast Public Health Unit
Phone: (07) 5509 7201
Email: Sharon_jurd@health.qld.gov.au
Weekend Produce Markets around Adelaide
A Survey of Horticultural Produce for Chemical Residues
Background to the Survey
The Food Section of the South Australian Department of Human Services (DHS) participated in a program that tested a large number of fresh fruits and vegetables that are sold from supermarkets and greengrocers for residues of agricultural chemicals such as pesticides and fungicides. The results show that most fresh produce from conventional retail outlets is free of residues or has low levels well within safe limits. Results of recent testing can be found by searching for ‘Pooraka Food-Care Project’ at www.safoodonline.com
Weekend produce markets, which appear to be growing in popularity near Adelaide, provide an opportunity for small-scale farmers and backyard growers to sell their produce direct to consumers. These growers may not have previously been subject to a testing program. The Food Section accordingly took a ‘snapshot’ of 80 samples from weekend markets to obtain a picture of how well the produce complies with legal requirements for chemical residues. If the survey indicated the presence of residues above approved levels, the Food Section would consider more comprehensive testing.
Standards
A variety of chemicals are approved for use on fruit and vegetable crops to prevent or control a range of pests and fungal diseases. There are maximum residue limits set for each type of chemical that is approved for use on specific crops. The chemicals approved for use are listed in Standard 1.4.2 of theAustralia New Zealand Food Standards Code. The Code can be viewed at www.foodstandards.gov.au
Which markets?
A total of 80 samples were purchased from the following markets in and around Adelaide.
- Torrens Island Market
- Gepps Cross Drive-in Market
- Willunga Farmers Market
- Pooraka weekend Market
- Junction Market
Torres Island Produce Market
What fruit and vegetables were tested?
Samples included: carrots, beans, snow peas, apples, tomatoes, pears, leeks, peaches, onions, coriander, cucumber, corn, plums, silverbeet, spinach, lettuce, cherries, parsley and grapes.
What chemicals did we test for?
Each sample was screened for 85 chemicals, including pesticides, herbicides, and fungicides. A total of 6,800 food and chemical combinations were examined.
Results
72 of the 80 samples (90%) were free of any residues.
All residues detected were well within the limits listed in the Food Standards Code:
Sample Chemical (type) Max Residue Limit (MRL) Level detected
carrots endosulphan (pesticide) 2.0 mg/kg 0.17 mg/kg
apples Iprodione (fungicide) 3.0 mg/kg 0.84 mg/kg
apples “ “ “ 0.24 mg/kg
pears “ “ “ 0.48 mg/kg
grapes “ “ “ 0.57 mg/kg
peaches “ “ “ 1.21 mg/kg
cherries “ “ “ 2.81 mg/kg
Procymidone (fungicide) 10.0 mg/kg 0.21 mg/kg
cherries “ “ “ 0.17 mg/kg
Iprodione (fungicide) 3.0 mg/kg 1.21 mg/kg
The ‘Snapshot Survey’ found no evidence to indicate that fresh horticultural produce sold from weekend markets poses a risk to consumers from the presence of agricultural chemicals. Growers and stallholders should remain diligent to ensure that proper agricultural practices continue to be observed. Further testing will be undertaken by the Food Section to confirm the safety of these foods.
Further information
Department of Human Services (DHS) – Food Section
Email: food@dhs.sa.gov.au or Phone: (08) 82267100
Quantitative Consumer Research on Labelling Issues
Providing adequate information on food labels to enable consumers to make an informed choice is one of the objectives of the Australian New Zealand Food Standards Code (the Code). In the recently revised Code several labelling changes have been introduced, such as date marking, mandatory nutrition information panels (NIPs), percentage ingredient labelling and allergen declarations (FSANZ 2002). To assess the impact of these labelling changes, FSANZ recently completed baseline research on food labelling issues for consumers and other stakeholders (ANZFA 2001, FSANZ 2002 1 , FSANZ 2003 ) .
The aim of the quantitative consumer research on labelling issues was to benchmark baseline indicators on consumer attitudes towards and knowledge and use of food labels, including consumer awareness and use of different label elements, beliefs about the clarity and trustworthiness of different label elements, and the elements that were difficult to interpret.
The quantitative survey results confirmed the preliminary qualitative findings that different consumers used food labels for different reasons and in different ways, and some used more label elements than others (ANZFA 2001 ) . For example, date marks were used more regularly for perishable foods, such as dairy foods, and allergen declarations were mostly used for baked products, such as biscuits.
Consumers reported that ingredient lists, NIPs, date marks, country of origin, percentage labels and nutrient claims were more 'top of mind' label elements than weight, price or brand (unprompted awareness). However, unprompted awareness on health claims, novel foods and irradiation was low. New Zealanders reported a higher prompted awareness and use of most label elements; for example, ingredient lists, NIPs, advisory statements, warning statements, GMO declarations, preparation and storage instructions, and novel food declarations. However, Australian consumers reported a higher awareness of nutrient claims, and a greater proportion reported using the country of origin label element than New Zealanders, reflecting different regulations in New Zealand for country of origin labelling.
On average, consumers reported using at least five label elements (range of 1 to 14) out of the 15 assessed. The most widely used label elements were date marking, ingredient lists and NIPs with over two thirds of consumers reporting their use. The least used elements were the genetically modified organism (GMO) declarations, health claims, allergen declarations, and novel and irradiated food declarations. With the exception of health claims, the other elements are only mandatory on labels where the food contains allergens, GMOs, novel or irradiated foods as ingredients. These mandatory declarations are new provisions in the Code and their awareness and use was expected to be lower compared to other label elements. There were two key reasons reported for label non-use: disinterest, habit or previous positive experiences with foods, and considering their use as being unnecessary.
The results also demonstrated that most consumers did not have difficulties in reading and interpreting the nutrient information contained in NIPs on single products. However, when comparing two similar products using the NIPs, consumers did not consider the overall nutritional value of the foods. When comparing two similar products, consumers focussed on one nutrient only, and fat levels dominated their evaluative thinking. Given the choice, many consumers opted for a product slightly lower in fat over a product where the difference in another nutrient e.g. sodium, was greater in magnitude and