Bacterial Pathogens in Dried Herbs and Dried Teas - April 1, 2014 to March 31, 2018
Food microbiology - Targeted Surveys - Final report
Summary
Dried aromatic herbs are widely used flavoring ingredients in food preparations. Dried teas including teas and herbal teas are used for brewing teas. Both dried herbs and teas are consumed globally and traded internationally. Dried herbs have been associated with numerous salmonellosis outbreaks worldwide, and dried teas have recently been associated with several recalls due to Salmonella contamination and a salmonellosis outbreak. Both dried herbs and teas are derived from agricultural products and can be contaminated with bacterial pathogens during primary production, processing, storage and packaging. Once contaminated, bacterial pathogens, such as Salmonella can survive for extended periods of time in these low-moisture products. Depending on the end use, for example if dried herbs are added to ready-to-eat (RTE) foods that undergo no further heat treatment, or dried teas are cold-brewed, the presence of bacterial pathogens creates a potential risk for foodborne illnesses.
Considering the factors mentioned above and their relevance to Canadians, dried herbs and dried teas were selected for targeted surveys. The purpose of this survey was to generate baseline information on the occurrence of pathogenic bacteria of concern in dried herb and tea products on the Canadian market.
Over the course of this study (April 1, 2014 to March 31, 2018), a total of 2680 dried herb samples and 1178 dried tea samples were collected from retail locations in 11 cities across Canada. All herb (2680) and tea (1178) samples were tested for generic Escherichia coli (E. coli) and the following bacterial pathogens: Salmonella species (spp.), Bacillus cereus (B. cereus) and Clostridium perfringens (C. perfringens). A portion of the dried herb samples (1773) and all of the dried tea samples (1178) were also tested for the bacterial pathogen Staphylococcus aureus (S. aureus). Generic E. coli is an indicator of the overall sanitation conditions throughout the food chain from production to the point of sale.
In this study, over 99.8% of the dried herb samples and over 99.5% of the dried tea samples were assessed as satisfactory. Presumptive B. cereus was found at elevated levels (104 < x ≤ 106 colony-forming units (CFU)/gram (g)) in two herb samples (0.07%, 2/2680) and five tea samples (0.4%, 5/1178). S. aureus was found at elevated levels (102 < x ≤ 104 CFU/g) in one herb sample (0.06% 1/1773). Salmonella spp. was identified in one herb sample (0.04%, 1/2680) and one tea sample (0.08%, 1/1178). High levels (> 103 most probable number (MPN)/g) of generic E. coli were found in two herb samples (0.07%, 2/2680).
In dried herb and tea products, the presence of elevated levels B. cereus (104 < x ≤ 106 CFU/g) or S. aureus (102 < x ≤ 104 CFU/g) could indicate that the food may have been produced under unsanitary conditions. The presence of high levels (>103 MPN/g) of generic E. coli could indicate inadequate sanitation controls during processing and/or at the processing facility.
The Canadian Food Inspection Agency (CFIA) conducted appropriate follow-up activities such as facility inspections and additional sampling. The Salmonella contaminated herb and tea samples resulted in product recalls. The two herb samples where high levels of generic E. coli were found resulted in the implementation of corrective actions by the processing facilities and one product recall as the product was considered to be RTE. There were no known reported illnesses associated with any of the contaminated herb or tea products.
Overall, our survey results indicate that most of the dried herbs and dried teas sampled appear to have been produced under sanitary conditions. However, contamination by bacterial pathogens such as Salmonella can occur occasionally, and a loss of sanitation controls along the food production chain can occur as well. 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?
Dried herbs are widely used flavoring ingredients in food preparations. Dried teas including teas (green, white, black and oolong) and herbal teas (blended herbs, spices and other plant material) are used for brewing teas. Dried herbs have been associated with numerous foodborne illness outbreaks worldwideFootnote 1 Footnote 2, and dried teas have recentlyFootnote 3 Footnote 4 been associated with several recalls due to Salmonella contamination and a salmonellosis outbreak Footnote 5. Both dried herbs and teas are derived from agricultural products and can be contaminated with bacterial pathogens during primary production, processing, storage and packaging. In addition, dried herbs and teas are consumed all over the world and are traded internationallyFootnote 6. Contaminated products can be distributed internationally and potentially cause foodborne illnesses in multiple countries. Depending on the end use of the product, for example, if dried herbs are added to RTE foods that undergo no further heat treatment, or dried teas are cold-brewed, the presence of bacterial pathogens creates a potential risk for foodborne illnesses.
Considering the factors mentioned above and their relevance to Canadians, dried herbs and dried teas were selected for targeted surveys. The purpose of this survey was to generate baseline information on the occurrence of generic E. coli and the following pathogenic bacteria: Salmonella spp., B. cereus, C. perfringens and S. aureus in dried herb and tea products on the Canadian market. Generic E. coli is an indicator of the overall sanitation conditions throughout the food chain from production to the point of sale.
What did we sample?
A sample consisted of a single or multiple unit(s) (individual consumer-size package(s) from a single lot) with a total weight of at least 100 g. All samples were collected from national and local/regional retail stores located in 11 major cities across Canada. These cities encompassed four geographical areas:
- Atlantic (Halifax and Saint John)
- Quebec (Quebec City, Montreal)
- Ontario (Toronto, Ottawa)
- West (Vancouver, Kelowna, Calgary, Saskatoon and Winnipeg).
The number of samples collected from these cities was in proportion to the relative population of the respective areas.
Dried herb samples were collected between April 1, 2014 to March 31, 2015 and April 1, 2016 to March 31, 2018. Dried tea samples including dried teas and dried herbal teas (blended herbs, spices or other plant material) were collected between April 1, 2016 and March 31, 2018. Sample collection and testing information can be found in table 1.
Product group | Survey year(s) | Analyses | Number of samples analyzed |
---|---|---|---|
Dried herbs (group i) |
2014-2015 | B. cereus C. perfringens Salmonella spp. Generic E. coli |
907 |
Dried herbs (group ii) |
2016-2017 2017-2018 |
B. cereus C. perfringens S. aureus Salmonella spp. Generic E. coli |
1773 |
Subtotal (dried herbs) | 2680 | ||
Dried teas | 2016-2017 2017-2018 |
B. cereus C. perfringens S. aureus Salmonella spp. Generic E. coli |
1178 |
Total | 3858 |
What analytical methods were used and how were samples assessed?
Samples were analyzed using analytical methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of FoodsFootnote 7. The assessment criteria used in this survey are based on the principles of the Health Products and Food Branch Standards and Guidelines for Microbiological Safety of Foods Footnote 8. At the time of writing this report, no assessment guidelines had been established in Canada for the presence of pathogenic bacteria in dried herbs and dried teas. Health Canada's guidelines for indicator organisms and bacterial pathogens in spices (ready-to-eat) Footnote 8 were applied in the assessment of dried herb and tea results (table 2).
Bacterial analysis | Method identification number Table Note a | Satisfactory assessment | Investigative assessment | Unsatisfactory assessment |
---|---|---|---|---|
Bacillus cereus | MFLP-42 | ≤ 104 CFU/g | 104 < x ≤ 106 CFU/g | > 106 CFU/g |
Clostridium perfringens | MFHHPB-23 | ≤ 104 CFU/g | 104 < x ≤ 106 CFU/g | > 106 CFU/g |
Staphylococcus aureus | MFHPB-21 | ≤ 102 CFU/g | 102 < x ≤ 104 CFU/g | > 104 CFU/g |
Salmonella spp. | MFHPB-20 | Absent in 25 g | Not Applicable (N/A) | Present in 25 g |
Generic E. coli | MFHPB-19 | ≤ 102 MPN/g | 102 < x ≤ 103 MPN/g | > 103 MPN/g |
Table Notes
- Table note a
-
The methods used were the published versions at the time of analysis
B. cereus, C. perfringens and S. aureus are commonly found in the environment and are bacteria that can produce protein toxins in contaminated food or in the intestines of infected humans, which can cause foodborne illness. Elevated levels of these bacteria (table 2) indicate that the food may have been produced under unsanitary conditions. Therefore,an investigative assessment which may result in further follow-up actions is associated with elevated levels of the bacteria. As the results are based on the analysis of one unit (n=1), further sampling may be required to verify the levels of the bacteria of the lot. The presence of high levels of these bacteria (table 2) is indicative of high enough levels of the bacterial toxins to cause foodborne illnesses. Therefore, samples with high levels of the bacteria 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 spp., 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 a food product are used to assess the overall sanitation conditions throughout the food chain from production to the point of sale. An investigative assessment is associated with elevated levels of generic E. coli (100 < x ≤ 1000 most probable number (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.
What were the survey results?
Group i dried herb samples (907) were tested for generic E. coli and the bacterial pathogens B. cereus, C. perfringens and Salmonella spp. (table 3). Group ii dried herb samples (1773) were tested for generic E. coli and the bacterial pathogens B. cereus, C. perfringens, S. aureus and Salmonella spp. C. perfringens (>104 CFU/g) was not found in any of the herb samples (2680). Presumptive B. cereus was found at elevated levels (104 < x ≤ 106 CFU/g) in two herb samples(0.07%, 2/2680). S. aureus was found at elevated levels (102 < x ≤ 104 CFU/g) in one herb sample (0.06% 1/1773). Salmonella spp. was identified in one herb sample (0.04%, 1/2680), which also contained an elevated level (102 < x ≤ 103 MPN/g) of generic E. coli. High levels (>103 MPN/g) of generic E. coli were found in two herb samples (0.07%, 2/2680).
All of the dried tea samples (1178) were tested for generic E. coli and the bacterial pathogens B. cereus, C. perfringens, S. aureus and Salmonella spp. (table 3). C. perfringens (>104 CFU/g), S. aureus (>102 CFU/g) and generic E. coli (>102 MPN/g) were not found in any of the tea samples. Presumptive B. cereus were found at elevated levels (104 < x ≤ 106 CFU/g) in five tea samples(0.4%, 5/1178). Salmonella spp. was identified in one tea sample (0.08%, 1/1178).
Analysis group | Analysis | Unsatisfactory (% of total samples) |
Investigative (% of total samples) |
Satisfactory (% of total samples) | Number of samples tested |
---|---|---|---|---|---|
Dried herbs (group i) | B. cereus | 0 | 2 | 903 | 907 |
C. perfringens | 0 | 0 | |||
Salmonella spp. | 1 Table Note b | N/A | |||
Generic E. coli | 1 | 0 | |||
Dried herbs (group ii) | B. cereus | 0 | 0 | 1771 | 1773 |
C. perfringens | 0 | 0 | |||
S. aureus | 0 | 1 | |||
Salmonella spp. | 0 | N/A | |||
Generic E. coli | 1 | 0 | |||
Subtotal (dried herbs) | 3 (0.1%) | 3 (0.1%) | 2674 (99.8%) | 2680 (100%) | |
Dried teas | B. cereus | 0 | 5 | 1172 | 1178 |
C. perfringens | 0 | 0 | |||
S. aureus | 0 | 0 | |||
Salmonella spp. | 1 | N/A | |||
Generic E. coli | 0 | 0 | |||
Subtotal (dried teas) | 1 (0.1%) | 5 (0.4%) | 1172 (99.5%) | 1178 (100%) | |
Total | 4 (0.1%) | 8 (0.2%) | 3846 (99.7%) | 3858 (100%) |
Table Notes
- Table note b
-
Elevated level (102-103 MPN/g) of generic E. coli also present.
Of the 2680 dried herb samples 6.7% were domestic and 67.7% were imported from more than 25 countries. The country where the product was processed could not be determined for 25.7% of the samples (table 4). Of the 1178 dried tea samples 19.0% were domestic and 59.2% were imported from more than 15 countries. The country where the product was processed could not be determined for 21.8% of the samples (table 5). In terms of production practice, 64.1% of dried herb samples and 68.2% of dried tea samples were conventional (tables 4 and 5).
Product origin | Total number of samples (%) | Conventional | Organic |
---|---|---|---|
Domestic | 179 (6.7) | 158 | 21 |
Imported | 1812 (67.6) | 921 | 891 |
Argentina | 5 | 0 | 5 |
Croatia | 2 | 0 | 2 |
Egypt | 147 | 5 | 142 |
France | 3 | 0 | 3 |
Germany | 2 | 2 | 0 |
Greece | 13 | 12 | 1 |
India | 37 | 28 | 9 |
Iran | 4 | 4 | 0 |
Israel | 13 | 2 | 11 |
Italy | 7 | 0 | 7 |
Lebanon | 9 | 9 | 0 |
Morocco | 28 | 14 | 14 |
Netherland | 2 | 0 | 2 |
Norway | 6 | 0 | 6 |
Peru | 4 | 0 | 4 |
Poland | 12 | 9 | 3 |
Romania | 5 | 0 | 5 |
Sri Lanka | 2 | 0 | 2 |
Tunisia | 3 | 0 | 3 |
Türkiye | 64 | 26 | 38 |
United States | 120 | 6 | 114 |
Other Table Note c | 5 | 2 | 3 |
Imported unknown | 1319 | 801 | 518 |
Unknown | 689 (25.7) | 639 (1 Table Note d) | 50 |
Total | 2680 (100) | 1718 (64.1) | 962 (35.9) |
Table Notes
- Table note c
-
Number of countries which represented only one sample
- Table note d
-
Salmonella contaminated sample
Product origin | Total number of samples (%) | Conventional | Organic |
---|---|---|---|
Domestic | 224 (19.0) | 192 (1 Table Note f) | 32 |
Imported | 697 (59.2) | 468 | 229 |
Argentina | 4 | 2 | 2 |
China | 57 | 31 | 26 |
Egypt | 22 | 7 | 15 |
France | 10 | 5 | 5 |
Germany | 80 | 61 | 19 |
Greece | 2 | 1 | 1 |
India | 76 | 25 | 51 |
Japan | 6 | 6 | 0 |
Kenya | 55 | 55 | 0 |
Lebanon | 15 | 15 | 0 |
European Union | 10 | 10 | 0 |
South Africa | 5 | 1 | 4 |
Poland | 18 | 18 | 0 |
Sri Lanka | 133 | 131 | 2 |
Vietnam | 2 | 0 | 2 |
United Kingdom | 20 | 20 | 0 |
United States | 80 | 21 | 59 |
Multiple | 2 | 1 | 1 |
Other Table Note e | 6 | 5 | 2 |
Imported unknown | 94 | 53 | 41 |
Unknown | 257 (21.8) | 143 | 114 |
Total | 1178 (100) | 803 (68.2) | 375 (31.8) |
Table Notes
- Table note e
-
Number of countries which represented only one sample
- Table note f
-
Salmonella contaminated sample
Dried herb and dried tea product types are detailed in table 6. A variety of dried herbs were collected representing 14 single and three mixed types (table 6). Dried tea samples were categorized into five tea types (black, green, oolong, white, and herbal) (table 7). Herbal teas (blended herbs, spices and other plant material) accounted for 51.4% of the dried tea samples.
Product type | Number of samples | % of total |
---|---|---|
Basil | 375 | 14 |
Bay leaves | 1 | 0.03 |
Chive | 1 | 0.03 |
Cilantro | 236 | 8.8 |
Dill | 110 | 4.1 |
Marjoram | 37 | 1.4 |
Mint | 12 | 0.4 |
Oregano | 436 | 16.3 |
Parsley | 157 | 5.9 |
Rosemary | 381 | 14.2 |
Sage | 231 | 8.6 |
Savoury | 72 | 2.7 |
Tarragon | 37 | 1.4 |
Thyme | 478 | 17.8 |
Herbs of provence | 10 | 0.4 |
Mixed italian herbs | 31 | 1.3 |
Mixed herbs | 75 | 2.8 |
Total | 2680 | 100 |
Product type | Tea types | Number of samples | % of total |
---|---|---|---|
Teas | Black tea | 298 | 25.3 |
Teas | Green tea | 227 | 19.3 |
Teas | Oolong tea | 21 | 1.8 |
Teas | White tea | 27 | 2.3 |
Herbal tea | n/a | 605 | 51.4 |
Total | 1178 | 100 |
Further details of each unsatisfactory and investigative sample are provided in table 8.
Product type | Unsatisfactory Salmonella |
Unsatisfactory Generic E. coli >103 CFU/g |
Investigative B. cereus 104 < x ≤ 106 CFU/g |
Investigative S. aureus 102 < x ≤ 104 CFU/g |
Number of samples tested per product type |
---|---|---|---|---|---|
Dried oregano (RTE) | 0 | 1 | 1 | 0 | 436 |
Dried rosemary | 1 | 1 | 0 | 0 | 381 |
Dried savory | 0 | 0 | 1 | 0 | 72 |
Dried tarragon | 0 | 0 | 0 | 1 | 37 |
Dried herbal tea | 1 Table Note g | 0 | 2 | 0 | 605 |
Dried green tea | 0 | 0 | 1 | 0 | 227 |
Dried black tea | 0 | 0 | 1 | 0 | 297 |
Dried white tea | 0 | 0 | 1 | 0 | 27 |
Total | 2 | 2 | 7 | 1 | N/A |
Table Notes
- Table note g
-
Elevated level (102 < x ≤103 CFU/g) of generic E. coli also present
What do the survey results mean?
In this study, over 99.8% of the dried herb samples and over 99.5% of the dried tea samples were assessed as satisfactory. C. perfringens (>104 CFU/g) was not found in any of the herb samples (2680). C. perfringens (>104 CFU/g), S. aureus (>102 CFU/g),and generic E. coli (>102 CFU/g) were not found in any of the tea samples (1178).
Salmonella spp., a common bacterial pathogen associated with foodborne illnesses, was identified in 0.04% (1/2680) of the herb samples and 0.08% (1/1178) of the tea samples. All Salmonella contaminated samples resulted in product recalls. B. cereus, a common bacterial pathogen in low-moisture foods, was found at elevated levels (104 < x ≤ 106 CFU/g) in 0.07% (2/2680) of the herb samplesand 0.4% (5/1178) of the tea samples. S. aureus was found at an elevated level (102 < x ≤ 104 CFU/g) in 0.06% (1/1173) of the herb samples. Samples where elevated levels of S. aureus and presumptive B. cereus were found could indicate that the food may have been produced under unsanitary conditions. High levels of generic E. coli (> 103 CFU/g) were found in 0.07% (2/2680) of the herb samples resulting in the implementation of corrective actions by the processing facilities and one product recall. There were no known reported illnesses associated with the any of the contaminated dried herb and dried tea products.
The prevalence of Salmonella spp. (0.04%, 95% CI: 0.01-0.21%) in dried herb samples identified in this survey appears slightly lower than the prevalence reported in a study conducted in the US. The US studyFootnote 9 investigated the prevalence of Salmonella in dried herbs collected from retail locations in the US between 2013 and 2014 and found Salmonella in 0.23% (4/1741, 95% CI: 0.09-0.59%) of the dried herb samples (basil, coriander, and oregano). A similar study conducted in the UK in 2004 reported the prevalence of Salmonella as being 1.21% (9/743, 95% CI: 0.64-2.29%) in retail dried herb samples (coriander, fenugreek, mint and sage). The UK study also reported the prevalence of B. cereus (and other Bacillus spp.)at levels >104 CFU/g as being 0.27% (2/743, 95% CI: 0.07-0.98%) in retail dried herbs. In comparison, the prevalence of presumptive B. cereus at levels >104 CFU/g (and below ≤ 106 CFU/g) was found to be 0.07% (2/2680, 95% CI: 0.02-0.27%) in retail dried herb samples (14 single and three mixed types) analysed in this study.
The prevalence of Salmonella spp. (0.08%, 95% CI: 0.01-0.48%) and presumptive B. cereus (0.4%, 95% CI: 0.18-0.99%) at elevated levels (104 < x ≤ 106 CFU/g) in dried tea samples were identified in the current study. To date, very few published studies investigating the microbiological safety and quality of dried teas have been conducted as dried teas have traditionally been brewed using boiling or hot water, serving as an effective microbial risk mitigation step. More recently, brewing teas in low temperature or ice water has become a common practice. A study Footnote 10 revealed that using boiling water or hot water (>80 °C) to brew teas from one to several minutes resulted in the complete inactivation of bacterial pathogens such as Salmonella from brewed teas Footnote 10. The study did discover that the use of low temperature water (below 55°C) to brew teas did not inactivate all of the bacterial pathogens Footnote 10. The study results Footnote 10 suggest that the practice of using low temperature water to brew teas contaminated with pathogens may result in foodborne illnesses in high risk population (such as infants Footnote 5 , elderly and people with a weak immune system).
Overall, our survey results indicate that most dried herb and dried tea products sampled appear to have been produced under sanitary conditions. However, our results do indicate that contamination by bacterial pathogens such as Salmonella can occur occasionally, and a loss of sanitation controls along the food production chain can occur as well. Consequently, as with all foods, safe handling practices are recommended for producers, retailers and consumers.
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