Food microbiology – Targeted surveys – Final report
Summary
A 2-year targeted surveyFootnote 1 analysed 107 samples of ready-to-eat (RTE) arctic surf clams for the presence of the pathogens Salmonella species (spp.) and Listeria monocytogenes (L. monocytogenes). All samples were also tested for generic Escherichia coli (E. coli) which is an indicator of the overall hygienic and sanitary conditions of the food supply chain from production to the point of sale.
All (100%) of the 107 samples tested were found to be satisfactory. Salmonella spp. and L. monocytogenes were not found in any of the samples. Generic E. coli (> 4 most probable number (MPN)/g) were not found in any of the samples.
Overall, our survey results indicate that Canadian harvested and processed arctic surf clams sold in Canada are generally safe for consumption. However, as with all foods, and especially with those that are RTE, good hygienic practices are recommended for producers, retailers, and consumers.
Why the survey was conducted
The survey was conducted to generate information on the quality and safety of prepackaged RTE arctic surf clams sold at retail in Canada.
Arctic surf clams are harvested for their meat, which is considered a delicacy in many countries. Arctic surf clams are typically harvested using specialized fishing vessels equipped with hydraulic dredges which are dragged along the ocean floor to scoop up the clams. The vessels target specific areas where arctic surf clams are known to inhabit, often in deeper waters off the coast of Atlantic CanadaFootnote 2. Once harvested, the clams are typically blanched and then frozen on board the vessels to preserve their freshness and extend their shelf life. The clams are then sorted at the processing facility and only those that are deemed to be sushi-grade are packaged for retail sale. Currently, the majority of the arctic surf clam harvested in Canada are exported to Asian countriesFootnote 3 such as Japan, China, and South Korea where they are consumed in sushi and sashimi dishes and known as hokkigaiFootnote 4. However, in recent years they have grown in popularity in Canada resulting in increased availability on the Canadian retail marketplace.
Contamination with bacterial pathogens can occur at any step in the food supply chain such as during harvesting, processing, and/or packaging. Consequently, if pathogens are present, there is a potential for foodborne illness as arctic surf clams are RTE.
When the survey was conducted
The survey was conducted over a 2-year period from April 1, 2021, to March 31, 2023.
Where the samples were collected from
Samples were collected from national retail chains and local/regional grocery stores located in the following 5 major cities across Canada:
- Montreal
- Toronto
- Ottawa
- Vancouver
- Calgary
The planned number of samples to be collected from each city was based on the population of the province in which the city was located relative to the total population of Canada.
Total number and description of samples collected
A total of 107 prepackaged RTE frozen arctic surf clam samples were collected, and all were harvested and packaged in Canada. It should be noted however that the scope of sampling was not restricted with respect to sample type (fresh or frozen) or origin (domestic or imported). A sample consisted of a single or multiple consumer sized packages of the same lot weighing at least 250 g.
What the samples were tested for
All samples were tested for Salmonella spp., L. monocytogenes, and generic E. coli. Salmonella spp. and L. monocytogenes are pathogenic bacteria while generic E. coli is an indicator of the overall hygienic and sanitary conditions under which the samples have been produced, processed, stored, and transported.
Methods used to test the samples
Samples were analyzed using analytical methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of FoodsFootnote 5 that were appropriate for the testing of arctic surf clams.
How the samples were assessed
The samples were assessed using criteria based on the principles of CFIA's Bacteriological guidelines for fish and fish products (end product)Footnote 6, and Health Canada's Policy on Listeria monocytogenes in Ready-to-Eat FoodsFootnote 7.
| Bacteria | Satisfactory | Investigative | Unsatisfactory |
|---|---|---|---|
| Salmonella spp. | Not detected | Not applicable | Detected |
| L. monocytogenes | Not detected |
Not applicable (category 1Table Note a) Detected and ≤ 102 CFU/g (category 2Table Note a) |
Detected (category 1Table Note a) > 102 CFU/g (category 2Table Note a) |
| Generic E. coli | ≤ 4 MPN/g | > 4 and ≤ 40 MPN/g | > 40 MPN/g |
Survey results
All (100%) of the 107 samples tested were found to be satisfactory. Salmonella spp. and L. monocytogenes were not found in any of the samples. Generic E. coli at elevated levels (> 4 MPN/g) were not found in any of the samples.
| Bacterial analysis | Number of samples tested | Satisfactory (%) | Investigative | Unsatisfactory |
|---|---|---|---|---|
| Salmonella spp. | 107 | 107 | Not applicable | 0 |
| L. monocytogenes | 107 | 107 | Not applicable | 0 |
| Generic E. coli | 107 | 107 | 0 | 0 |
| Total | 107Table Note b | 107 (100) | 0 | 0 |
What the survey results mean
No previously published studies on the microbiological quality or safety of arctic surf clams were found at the time of writing this report.
Overall, our survey results indicate that arctic surf clams sold in Canada are generally safe for consumption. However, as with all foods, and especially with those that are RTE, good hygienic practices are recommended for producers, retailers and consumers.
What is done with the survey results
All results are used to:
- inform risk management decisions
- support program design and re-design
Where to access the survey data
The data will be accessible on the Open Government Portal.