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Bacterial Pathogens in Pre-Prepared, Refrigerated Baked Desserts – April 1, 2016 to March 31, 2018

Food microbiology – Targeted surveys – Final report

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Summary

Refrigerated baked desserts are considered ready-to-eat (RTE) as they do not require any further preparation before consumption. Store-bought, pre-prepared, refrigerated baked goods are popular across all age groups due to their convenience. Unfortunately, some of these products have been associated with recalls and outbreaks of foodborne illnesses in Canada and worldwide. RTE foods, as with all foods can be contaminated with pathogens during production, handling, packaging and distribution. However, as these products are consumed "as is," the presence of bacterial pathogens represents an increased potential risk for foodborne illnesses.

Considering the factors mentioned above and their relevance to Canadians, a variety of refrigerated baked desserts were selected for targeted surveys. The primary food safety concern with respect to refrigerated RTE basked desserts is cross-contamination during the addition of pre-prepared glazes, icing, decorations, etc. post-baking. As the products do not undergo further processing (for example, a heat treatment), any pathogens that may be present in the glazes, icing, etc. or transferred from the environment or handler will not be inactivated. Consequently, all samples tested in this survey had either a sugar glaze or dairy spread (filling, icing etc.) added after baking.

The purpose of this survey was to generate baseline information on the occurrence of indicator and pathogenic bacteria in this type of RTE food at retail in Canada. Over the course of this two-year study (April 1, 2016 to March 31, 2018), a total of 2975 samples were collected from retail locations in 11 cities across Canada. All samples were tested for generic Escherichia coli (E. coli) and various pathogens (Bacillus cereus (B. cereus), Clostridium perfringens (C. perfringens), Staphylococcus aureus (S. aureus), Listeria monocytogenes (L. monocytogenes), Salmonella species (spp.)). Generic E. coli is an indicator organism as the levels at which they are found in foods is used to assess the overall sanitation conditions throughout the food production chain.

C. perfringens (>100 Colony Forming Unit (CFU)/gram (g)) and Salmonella spp. were not found in any samples. Presumptive B. cereus was detected at elevated levels (103 < x ≤ 104 CFU/g) in 3/2975 (0.10%) of the samples. S. aureus was detected at elevated levels (102 < x ≤ 104 CFU/g) in 1/2975 (0.03%) samples and L. monocytogenes (< 5 CFU/g) was detected in 1/2975 (0.03%) sample. Generic E. coli at elevated levels (1.8 < x ≤ 1x103 Most Probable Number (MPN)/g) were detected in 12/2975 (0.4%) samples.

In bakery products, the presence of elevated levels of presumptive B. cereus (103 < x ≤ 104 CFU/g), S. aureus (102 < x ≤ 104 CFU/g) and generic E. coli (1.8 < x ≤ 1x103 MPN/g) indicate that the food may have been produced under unsanitary conditions. Depending on the product and levels found, samples containing L. monocytogenes may have been produced under unsanitary conditions, and may be unfit for human consumption.

The Canadian Food Inspection Agency (CFIA) conducted appropriate follow-up activities such as facility inspections. Corrective and preventive actions were implemented by the manufacturing facilities. No reported illnesses were associated with any of the contaminated products.

Overall, our survey results suggest that almost all RTE refrigerated baked desserts available for purchase at retail in Canada are safe for consumption. They can however be found to be contaminated with pathogens and indicator organisms such as those found in this study: B. cereus, S. aureus, L. monocytogenes and generic E. coli. Consequently, as with all foods, safe handling practices are recommended for producers, retailers and consumers.

What are targeted surveys?

Targeted surveys are used by the CFIA to focus its surveillance activities on areas of highest health risk. The information gained from these surveys provides support for the allocation and prioritization of the Agency's activities to areas of greater concern. Originally started as a project under the Food Safety Action Plan (FSAP), targeted surveys have been embedded in the CFIA's regular surveillance activities since 2013. Targeted surveys are a valuable tool for generating information on certain hazards in foods, identifying and characterizing new and emerging hazards, informing trend analysis, prompting and refining health risk assessments, highlighting potential contamination issues, as well as assessing and promoting compliance with Canadian regulations.

Food safety is a shared responsibility. The CFIA works with federal, provincial, territorial and municipal governments and provides regulatory oversight of the food industry to promote safe handling of foods throughout the food production chain. The food industry and retail sectors in Canada are responsible for the food they produce and sell, while individual consumers are responsible for the safe handling of the food they have in their possession.

Why did we conduct this survey?

Refrigerated baked desserts are considered to be RTE foods as they do not require any further preparation before consumption. Store-bought, pre-prepared refrigerated baked goods are popular across all age groups due to their convenience. Unfortunately, some of these products have been associated with recalls and outbreaks of foodborne illnesses in CanadaFootnote 1Footnote 2 and worldwideFootnote 3Footnote 4Footnote 5. RTE foods, as with all foods can be contaminated with pathogens during production, handling, packaging and distribution. However, as these products are consumed "as is," the presence of bacterial pathogens represents an increased potential risk for foodborne illnesses.

Considering the factors mentioned above and their relevance to Canadians, a variety of refrigerated RTE baked desserts were selected for targeted surveys over a two year period from April 1, 2016 to March 31, 2018. The primary food safety concern with respect to refrigerated RTE basked desserts is cross-contamination during the addition of pre-prepared glazes, icing, decorations, etc. post-baking. As the products do not undergo further processing (for example, a heat treatment), any pathogens that may be present in the glazes, icing, etc. or transferred from the environment or handler will not be inactivated. While less likely, there is also a concern that pathogens if present prior to baking may survive the baking process and multiply if the product is not cooled down fast enough after baking. Consequently, all samples tested in this survey had either a sugar glaze or dairy spread (filling, icing, etc.) added after baking. This survey was implemented to gain further information on the occurrence of generic E. coli and various pathogens (B. cereus, C. perfringens, Salmonella spp., S. aureus, L. monocytogenes) in this product type at retail in Canada. Generic E. coli is an indicator organism as the levels at which they are found in foods is used to assess the overall sanitation conditions throughout the food production chain.

What did we sample?

For this survey, a sample consisted of one or multiple unit(s) (individual consumer-size package(s)) from a single lot with a total weight of at least 250g. All samples were collected from national retail chains and local/regional grocery stores located in 11 major cities across Canada. These cities encompassed four geographical areas:

The number of samples collected from these cities was in proportion to the relative population of the respective areas.

A variety of domestic and imported refrigerated RTE baked goods (cake, pastries, breads, tarts, etc.) with a sugar glaze or dairy spread (filling, icing etc.) added after baking were sampled. Sample collection was evenly distributed throughout the survey period (April 1, 2016 to March 31, 2018).

What analytical methods were used and how were samples assessed?

Samples were analyzed using methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of FoodsFootnote 6 (Table 1). The assessment criteria used in this survey (table 1) are based on the principles of Health Canada's Health Products and Food Branch Standards and Guidelines for Microbiological Safety of FoodsFootnote 7 or in the absence of Health Canada's Guidelines, on other international food safety authorities' microbiological guidelinesFootnote 8Footnote 9Footnote 10Footnote 11.

Table 1 – Analytical methods and assessment criteria for pre-prepared refrigerated baked dessert samples
Bacterial analysis Method identification numberTable Note a Satisfactory Investigative Unsatisfactory
Salmonella spp. MFHPB-20 Absent in 25g Not Applicable (N/A) Present in 25g
S. aureus MFHPB-21 ≤ 102 CFU/g 102 < x ≤ 104 CFU/g > 104 CFU/g
B. cereus MFLP-42 ≤ 103 CFU/g 103 < x ≤ 104 CFU/g > 104 CFU/g
C. perfringens MFHPB-23 ≤ 102 CFU/g 102 < x ≤ 103 CFU/g > 103 CFU/g
L. monocytogenes MFHPB-30
MFLP-28
MFLP-74
Absent in 25g N/A
(category 1Table Note b)
Present in 25g
(category 1Table Note b)
Present and ≤ 102 CFU/g
(category 2Table Note b)
> 102 CFU/g
(category 2Table Note b)
Generic E. coli MFHPB-19 ≤ 1.8 MPN/g 1.8 < x ≤ 1x103 MPN/g > 1x103 MPN/g

Table Notes

Table note a

The methods used were the published versions at the time of analysis

Return to table note a  referrer

Table note b

The pH and water activity of the sample were used to determine the product category

Return to table note b  referrer

At the time of writing of this report, no assessment guidelines had been established in Canada for the presence of B. cereus, C. perfringens or L. monocytogenes in bakery products. The assessment guidelines for L. monocytogenes are based on Health Canada's Policy on Listeria monocytogenes in RTE foodsFootnote 12 and are dependent upon the sample type analysed (category 1, 2A or 2B).

C. perfringens and B. cereus are commonly found in the environment and are bacteria that can produce protein toxins when present in high levels in foods or in the intestines of infected humans, which can cause foodborne illness. An investigative assessment which may result in further follow-up actions is associated with elevated levels (table 1). As the results are based on the analysis of one unit (n=1), further sampling may be required to verify their levels in the lot. The presence of high levels of these organisms (table 1) is indicative of the potential to cause foodborne illnesses. Therefore, samples with high levels of C. perfringens or B. cereus are assessed as unsatisfactory indicating that follow-up activities are warranted. The B. cereus method used in this survey is unable to discriminate B. cereus from other closely related organisms and therefore results are considered presumptive for B. cereus.

Unlike harmful bacterial pathogens such as Salmonella, generic E. coli is commonly found in the intestines of humans and most strains are harmless. It is considered to be an indicator organism and levels of generic E. coli found in foods are used to assess the overall sanitation conditions throughout the food chain from production to the point of sale. For bakery products, an investigative assessment is associated with elevated levels of generic E. coli (1.8 < x ≤ 1000 MPN/g), which may result in further follow-up actions. As the results are based on the analysis of one unit (n=1), further sampling may be required to verify the levels of generic E. coli of the lot. An unsatisfactory assessment is associated with high levels of generic E. coli (> 1000 MPN/g) as it may indicate a breakdown in good manufacturing practices (sanitation practices), and therefore possibly warranting the initiation of follow-up activities to determine the source of contamination and improve sanitation conditions along the food chain.

What were the survey results?

Over the course of this two-year study (April 1, 2016 to March 31, 2018), a total of 2975 samples were collected from retail locations in 11 cities across Canada. All samples were tested for B. cereus, C. perfringens, S . aureus, L. monocytogenes, Salmonella spp., and generic E. coli.

C. perfringens (>100 CFU/g)and Salmonella spp. were not found in any samples. Presumptive B. cereus was detected at elevated levels (103 < x ≤ 104 CFU/g) in 3/2975 (0.10%) of the samples. S. aureus was detected at elevated levels (102 < x ≤ 104 CFU/g) in 1/2975 (0.03%) samples and L. monocytogenes was detected (<102 CFU/g) in 1/2975 (0.03%) sample. Elevated levels of generic E. coli (1.8 < x ≤ 1x103 MPN/g) were detected in 12/2975 (0.4%) samples (table 2).

Table 2 – Assessment results of bacterial analyses in pre-prepared refrigerated baked dessert samples
Bacterial analysis Number of samples tested Satisfactory Investigative Unsatisfactory
Salmonella spp. 2975 2958 N/A 0
S. aureus 1 0
L. monocytogenes 1 0
B. cereus 3 0
C. perfringens 0 0
Generic E. coli 12 0
Total 2975 2958 17 0

Of the 2975 samples tested, 1206 (41%) were domestic and 57 (2%) were imported (table 4). The country where the desserts were produced could not be determined (unknown origin) for 1712 (58%) samples.

Table 3 – Assessment results of pre-prepared refrigerated baked dessert samples by product origin
Product origin Number of samples tested
(% of total samples)
Satisfactory Investigative
Generic E. coli
(1.8 < x ≤ 103 MPN/g)
Investigative
B.cereus
(103 < x ≤ 104 CFU/g)
Investigative
L. monocytogenes
(Present and <102
CFU/g – Category 2)
Investigative
S. aureus
(102 < x ≤ 104 CFU/g)
Domestic 1206
(41%)
1199 5 0 1 1
Import 57
(2%)
57 0 0 0 0
Unknown 1712
(58%)
1702 7 3 0 0
Total 2975 2958 12 3 1 1

A variety of RTE product types were analysed (table 4).

Table 4 – Assessment results of pre-prepared refrigerated baked dessert samples by product type
Product type Number of samples tested Satisfactory Investigative
Generic E. coli
(1.8 < x ≤ 103 MPN/g)
Investigative
B.cereus
(103 < x ≤ 104 CFU/g)
Investigative
L. monocytogenes
(Present and < 102
CFU/g-Category 2)
Investigative
S. aureus
(102 < x ≤ 104 CFU/g)
Bread with sugar/dairy topping 2 2 0 0 0 0
Cake with sugar/dairy topping 2697 2682 11 2 1 1
Cookie with sugar/dairy topping 7 7 0 0 0 0
Mousse with sugar/dairy topping 8 8 0 0 0 0
Pastry with sugar/dairy topping 261 259 1 1 0 0
Total 2975 2958 12 3 1 1

Further details about each investigative sample are provided in table 5.

Table 5 – Product and analytical information about investigative pre-prepared refrigerated baked dessert samples
Generic E. coli (n=12)
(1.8 < x ≤ 103 MPN/g)
B. cereus (n=3)
(103 < x ≤ 104 CFU/g)
Cake (n=11)
Pie (n=1)
Domestic (n=5)
Unknown Country of Origin (n=7)
Tarts (n=2)
Cake (n=1)
Unknown Country of Origin (n=3)
L. monocytogenes (n=1)
(Present and <102 CFU/g – Category 2)
S. aureus (n=1)
(102 < x ≤ 104 CFU/g)
Brownie
Domestic
Cake
Domestic

What do the survey results mean?

In this survey, all (100%) of the RTE bakery product samples tested were free of C. perfringens (>100 CFU/g) and Salmonella spp. Presumptive B. cereus was detected at elevated levels (103 < x ≤ 104 CFU/g) in 3/2975 (0.10%) of the samples tested. S. aureus was detected at elevated levels (102 < x ≤ 104 CFU/g) in 1/2975 (0.03%) samples tested. L. monocytogenes was detected (<102 CFU/g) in 1/2975 (0.03%) samples. Elevated levels of generic E. coli (1.8 < x ≤ 1x103 MPN/g) were detected in 12/2975 (0.4%) samples tested (table 2).

Studies similar to ours were conducted in IndiaFootnote 13 and DenmarkFootnote 14. The study conducted in India investigated the presence of S. aureus in various bakery products from five local bakeries and found the presence of S. aureus in a variety of products (such as plain cakes, puffs, cake with sugar and cream layer) ranging in counts from <10 to 6.5 x 104 CFU/g. The study did not find any S. aureus in bread or buns. The Danish study published in 2005 investigated the presence of B. cereus (and B. thuringiensis) in various RTE foods including desserts. The study found the presence of B. cereus-like organisms at levels of 103 < x ≤ 104 CFU/g in 1.5% of cream-cakes (n=4948) tested. The study found B. cereus-like organisms at levels of > 104 CFU/g in 0.8% of cream-cakes (n=4948) tested. The prevalence rates reported in the Danish study are higher than those reported in our study.

No trends were observed in our study with respect to product origin (table 3) or product type (table 4).

The CFIA conducted appropriate follow-up activities such as facility inspections. Corrective and preventive actions were implemented by the manufacturing facilities. No reported illnesses were associated with any of the contaminated products.

Overall, our survey results suggest that almost all RTE refrigerated baked desserts available for purchase at retail in Canada are safe for consumption. They can however be found to be contaminated with pathogens and indicator organisms such as those found in this study: B. cereus, S. aureus, L. monocytogenes and generic E. coli. Consequently, as with all foods, safe handling practices are recommended for producers, retailers and consumers.

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