Comment: Does the addition of those preservatives that have a long history of safe use need to be viewed as a preventive control? It does warrant discussion when conducting the hazard analysis. If one had to gauge the likelihood of occurrence, it would probably be unlikely with having good standard procedures in place.
- "Calcium propionate (E 282) is an organic salt of propionic acid [23] commonly used in bakery products to inhibit moulds and prolong shelf life. It is authorized as a food additive in the EU [10], and its specific purity criteria have been defined in the EU legislation"
- "The EFSA Panel on Food Additives and Nutrient Sources Added to Food re-evaluated the safety of propionates in 2014 and concluded that the available toxicity data did not allow for the allocation of an acceptable daily intake value [23]. Also, the US Food and Drug Administration (FDA) considered calcium propionate as safe to be used in foods [25]. Our investigation suggests that the ingestion of large amounts of calcium propionate can cause gastrointestinal irritation."
Eurosurveillance
https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2026.31.11.2600185
Calcium propionate in tortillas – a likely cause of a large outbreak of acute gastrointestinal illness, Finland, 2023
Veera Varo, Elina Leinonen , Annukka Markkula, Minna Anthon, Marja Raatikainen, Maria Tirkkonen, Nina Gynther, Heidi Landgren, Merja Korkalainen, Ruska Rimhanen-Finne
Selected Sections from Journal article
Discussion
We describe an outbreak involving over 700 students and school staff associated with consumption of flour tortillas served at school lunch in one municipality in Finland in 2023. Our investigation indicated that an excessive amount of the preservative calcium propionate in the tortillas was the likely cause of the outbreak. The likelihood of having gastrointestinal symptoms was three times higher for those eating tortillas than for those who had not eaten them. Albeit few samples tested, we measured nine times higher concentrations of calcium in tortillas packed within 9 min in the afternoon compared with tortillas from the same lot and packaged later that day. Calcium propionate was analysed in three tortilla samples with high calcium content, and 10 times higher concentrations were measured compared with samples from two tortillas produced later. The concentrations exceeded the highest permitted use amount of the additive in tortillas in the EU (2,000 mg/kg) [18]. An unusual vinegar-like odour could have been due to propionic acid, since it is known to have a pungent and rancid odour [19]. The food control authorities in the country where the tortillas were produced were contacted via the ACN to obtain information on any possible explanations in the production process or in the manufacturing of the implicated tortilla batch that could account for the abnormal calcium propionate concentration. The manufacturer did not identify any cause in the production process for the elevated concentrations of calcium propionate.
Several outbreaks of gastrointestinal illness associated with flour tortillas were reported in the US between 1997 and 2004 [20-22]. Most of them occurred in schools and were characterised by short incubation periods and durations of illness. In the outbreaks, no aetiological agent was identified, but symptoms suggested either a biotoxin or a chemical agent. Elevated calcium propionate concentrations were measured in tortillas in three of these outbreaks [22]. Like in our investigation, high calcium propionate concentrations could have been the cause of at least some of the previous outbreaks in the US. After the US outbreaks in 2003–2004, the manufacturer changed the tortilla recipe and reduced the amount of calcium propionate used in its product [21], which may explain why similar outbreaks were no longer reported in the US.
Calcium propionate (E 282) is an organic salt of propionic acid [23] commonly used in bakery products to inhibit moulds and prolong shelf life. It is authorised as a food additive in the EU [10], and its specific purity criteria have been defined in the EU legislation [11]. In 2016, tortillas were added to the category ‘breads and rolls’ in the appendix of the EU regulation as calcium propionate may be used in these food products as a preservative to extend shelf life [18]. Even though calcium propionate is not classified as an irritant, propionic acid is known to be corrosive to mucous membranes [24]. Large differences exist in the tolerance to propionic acid between different animal species. The EFSA Panel on Food Additives and Nutrient Sources Added to Food re-evaluated the safety of propionates in 2014 and concluded that the available toxicity data did not allow for the allocation of an acceptable daily intake value [23]. Also, the US Food and Drug Administration (FDA) considered calcium propionate as safe to be used in foods [25]. Our investigation suggests that the ingestion of large amounts of calcium propionate can cause gastrointestinal irritation.
Food-borne outbreaks with large numbers of cases, sudden-onset symptoms and chemical agent as a likely cause are unusual in Finland. In 2010, sudden-onset symptoms were seen in several outbreaks associated with consumption of raw beetroot [26]. Between 2010 and 2022, chemical agents were considered causing 18 reported food-borne outbreaks with 153 estimated cases. Chemicals are rarely reported causes of outbreaks and complaints about a specific product on the market exceeding toxicity limits are uncommon [14]. A chemical causing a food-borne outbreak may also go unrecognised since identifying the contaminants originating from food production, food processing or packaging can be challenging [27]. Our investigation reminds us of chemical agents as potential causes of food-borne outbreaks and underscores the need for strengthened surveillance in Europe to identify them.
In addition to calcium propionate, we investigated other possible causes. Tests for toxins were selected based on the symptoms and the acute onset, and the availability of analytical methods was also considered. We did not find evidence for B. cereus emetic toxin and staphylococcal enterotoxins, common in food-borne outbreaks [28,29], based on negative culture and toxin results. We also investigated contaminants such as mycotoxins, moulds and metals (cadmium, copper, iron, zinc), with all results within acceptable limits. Because of reports of a soapy taste in the tortillas, we considered detergent contamination as a possible cause. These substances can cause gastrointestinal symptoms [30], but reliable methods for detecting them in food are lacking [21]. Phosphorus levels, a possible indicator of industrial detergents, were within the normal range, and the amount required to cause symptoms would likely have made the food unpalatable [21]. Rancid oil has previously been associated with outbreaks [31,32]. However, rancidity in dry foods requires extended exposure to oxygen [33], and since the tortilla packages were opened just before serving, we considered this unlikely.
The vegetable filling, containing Quorn (Fusarium venenatum) and red kidney beans, was also investigated. Quorn and kidney beans have been linked to mild gastrointestinal symptoms [34-36], but lectin levels were below the detection limit, and the short incubation period did not support this cause [36]. Tracing of the ingredients further supported that the filling and salad components were not the source. Based on the clinical picture and possible intermediary foods, testing of nitrites was not considered appropriate.
There were limitations in this study. The causal relationship between calcium propionate consumption and the illness was not proven, since no samples were taken from the cases. To promote this, municipal and regional food-borne outbreak preparedness plans could emphasise the collection of patient samples. For example, vomit samples were used for toxin analysis in previous sudden-onset outbreaks in Finland [26]. We recommend obtaining clinical samples from 5–10 symptomatic individuals in future outbreaks. As in many observational studies, bias and confounding cannot be ruled out [37]. Although the questionnaire was distributed promptly, the respondents may have discussed the taste and suspected the tortillas beforehand, possibly influencing their responses.
The outbreak also revealed gaps in communication. The central kitchen, not the schools, reported the symptomatic students to the authorities after being contacted by the satellite kitchens about the ill students. The schools lacked an internal reporting system, and staff considered symptom information confidential and did not share it. We recommend clearer protocols for schools to report sudden illness and interrupt meal service when needed. Early contact with public health authorities enables timely response and sample collection.
Despite these challenges, the MEHA responded rapidly. Food samples and packaging were quickly secured, and efficient coordination between kitchens enabled same day traceback investigations. Food safety management practices of kitchens and distributors further supported the investigation through accurate records and retained food samples.
Conclusion
Selected Sections from Journal article
Discussion
We describe an outbreak involving over 700 students and school staff associated with consumption of flour tortillas served at school lunch in one municipality in Finland in 2023. Our investigation indicated that an excessive amount of the preservative calcium propionate in the tortillas was the likely cause of the outbreak. The likelihood of having gastrointestinal symptoms was three times higher for those eating tortillas than for those who had not eaten them. Albeit few samples tested, we measured nine times higher concentrations of calcium in tortillas packed within 9 min in the afternoon compared with tortillas from the same lot and packaged later that day. Calcium propionate was analysed in three tortilla samples with high calcium content, and 10 times higher concentrations were measured compared with samples from two tortillas produced later. The concentrations exceeded the highest permitted use amount of the additive in tortillas in the EU (2,000 mg/kg) [18]. An unusual vinegar-like odour could have been due to propionic acid, since it is known to have a pungent and rancid odour [19]. The food control authorities in the country where the tortillas were produced were contacted via the ACN to obtain information on any possible explanations in the production process or in the manufacturing of the implicated tortilla batch that could account for the abnormal calcium propionate concentration. The manufacturer did not identify any cause in the production process for the elevated concentrations of calcium propionate.
Several outbreaks of gastrointestinal illness associated with flour tortillas were reported in the US between 1997 and 2004 [20-22]. Most of them occurred in schools and were characterised by short incubation periods and durations of illness. In the outbreaks, no aetiological agent was identified, but symptoms suggested either a biotoxin or a chemical agent. Elevated calcium propionate concentrations were measured in tortillas in three of these outbreaks [22]. Like in our investigation, high calcium propionate concentrations could have been the cause of at least some of the previous outbreaks in the US. After the US outbreaks in 2003–2004, the manufacturer changed the tortilla recipe and reduced the amount of calcium propionate used in its product [21], which may explain why similar outbreaks were no longer reported in the US.
Calcium propionate (E 282) is an organic salt of propionic acid [23] commonly used in bakery products to inhibit moulds and prolong shelf life. It is authorised as a food additive in the EU [10], and its specific purity criteria have been defined in the EU legislation [11]. In 2016, tortillas were added to the category ‘breads and rolls’ in the appendix of the EU regulation as calcium propionate may be used in these food products as a preservative to extend shelf life [18]. Even though calcium propionate is not classified as an irritant, propionic acid is known to be corrosive to mucous membranes [24]. Large differences exist in the tolerance to propionic acid between different animal species. The EFSA Panel on Food Additives and Nutrient Sources Added to Food re-evaluated the safety of propionates in 2014 and concluded that the available toxicity data did not allow for the allocation of an acceptable daily intake value [23]. Also, the US Food and Drug Administration (FDA) considered calcium propionate as safe to be used in foods [25]. Our investigation suggests that the ingestion of large amounts of calcium propionate can cause gastrointestinal irritation.
Food-borne outbreaks with large numbers of cases, sudden-onset symptoms and chemical agent as a likely cause are unusual in Finland. In 2010, sudden-onset symptoms were seen in several outbreaks associated with consumption of raw beetroot [26]. Between 2010 and 2022, chemical agents were considered causing 18 reported food-borne outbreaks with 153 estimated cases. Chemicals are rarely reported causes of outbreaks and complaints about a specific product on the market exceeding toxicity limits are uncommon [14]. A chemical causing a food-borne outbreak may also go unrecognised since identifying the contaminants originating from food production, food processing or packaging can be challenging [27]. Our investigation reminds us of chemical agents as potential causes of food-borne outbreaks and underscores the need for strengthened surveillance in Europe to identify them.
In addition to calcium propionate, we investigated other possible causes. Tests for toxins were selected based on the symptoms and the acute onset, and the availability of analytical methods was also considered. We did not find evidence for B. cereus emetic toxin and staphylococcal enterotoxins, common in food-borne outbreaks [28,29], based on negative culture and toxin results. We also investigated contaminants such as mycotoxins, moulds and metals (cadmium, copper, iron, zinc), with all results within acceptable limits. Because of reports of a soapy taste in the tortillas, we considered detergent contamination as a possible cause. These substances can cause gastrointestinal symptoms [30], but reliable methods for detecting them in food are lacking [21]. Phosphorus levels, a possible indicator of industrial detergents, were within the normal range, and the amount required to cause symptoms would likely have made the food unpalatable [21]. Rancid oil has previously been associated with outbreaks [31,32]. However, rancidity in dry foods requires extended exposure to oxygen [33], and since the tortilla packages were opened just before serving, we considered this unlikely.
The vegetable filling, containing Quorn (Fusarium venenatum) and red kidney beans, was also investigated. Quorn and kidney beans have been linked to mild gastrointestinal symptoms [34-36], but lectin levels were below the detection limit, and the short incubation period did not support this cause [36]. Tracing of the ingredients further supported that the filling and salad components were not the source. Based on the clinical picture and possible intermediary foods, testing of nitrites was not considered appropriate.
There were limitations in this study. The causal relationship between calcium propionate consumption and the illness was not proven, since no samples were taken from the cases. To promote this, municipal and regional food-borne outbreak preparedness plans could emphasise the collection of patient samples. For example, vomit samples were used for toxin analysis in previous sudden-onset outbreaks in Finland [26]. We recommend obtaining clinical samples from 5–10 symptomatic individuals in future outbreaks. As in many observational studies, bias and confounding cannot be ruled out [37]. Although the questionnaire was distributed promptly, the respondents may have discussed the taste and suspected the tortillas beforehand, possibly influencing their responses.
The outbreak also revealed gaps in communication. The central kitchen, not the schools, reported the symptomatic students to the authorities after being contacted by the satellite kitchens about the ill students. The schools lacked an internal reporting system, and staff considered symptom information confidential and did not share it. We recommend clearer protocols for schools to report sudden illness and interrupt meal service when needed. Early contact with public health authorities enables timely response and sample collection.
Despite these challenges, the MEHA responded rapidly. Food samples and packaging were quickly secured, and efficient coordination between kitchens enabled same day traceback investigations. Food safety management practices of kitchens and distributors further supported the investigation through accurate records and retained food samples.
Conclusion
An excessive amount of preservative calcium propionate in flour tortillas was the likely cause of gastrointestinal illness in ca 700 people during or after school meals in one Finnish municipality. Our findings remind us of chemical agents as causes of food-borne outbreaks and the need for enhanced surveillance in Europe. Schools should be better prepared for sudden-onset food-borne outbreaks, and guidelines to interrupt school meals for safety reasons should exist.
Background
Chemicals can enter food either unintentionally or intentionally. Unintentional contamination may occur through environmental pollutants, processing, packaging or raw materials [1-4]. Chemical reactions during processing may also produce harmful by-products [1,3]. Additionally, cleaning agents, detergents and sanitisers used in food production may contribute to contamination of food products [3,4]. Natural toxins in plants, such as lectins in beans, may also pose health risks [5]. Residues from legally used agricultural chemicals and medicines may remain in food, and food spoilage can lead to the formation of toxic mycotoxins [6]. The European Union (EU) legislation sets maximum levels for contaminants and residues to ensure food safety [7,8].
In contrast, food additives are intentionally added to food to improve shelf life, flavour, texture or appearance [1,9]. Over 300 additives are authorised for use within the EU, each with specific conditions for use and maximum permitted concentrations as defined by the legislation [10,11].
Health effects from chemical contaminants are most often considered chronic, resulting from long-term, low-level exposure [2,12]. However, certain chemicals can cause acute illness with rapid symptom onset, depending on the amount or concentration of exposure [13]. Compared with biological agents, food-borne outbreaks caused by chemicals are less frequently reported [14]. Moreover, comprehensive EU data are lacking, as reporting of food-borne outbreaks to European Food Safety Authority (EFSA) does not include outbreaks caused by most chemical agents, except for biotoxins and microbial biogenic amines [15]. In Finland, food-borne and waterborne outbreaks caused by biological and chemical agents are reported by municipal authorities to the national Food- and Waterborne Outbreak (FWO) Registry.
Background
Chemicals can enter food either unintentionally or intentionally. Unintentional contamination may occur through environmental pollutants, processing, packaging or raw materials [1-4]. Chemical reactions during processing may also produce harmful by-products [1,3]. Additionally, cleaning agents, detergents and sanitisers used in food production may contribute to contamination of food products [3,4]. Natural toxins in plants, such as lectins in beans, may also pose health risks [5]. Residues from legally used agricultural chemicals and medicines may remain in food, and food spoilage can lead to the formation of toxic mycotoxins [6]. The European Union (EU) legislation sets maximum levels for contaminants and residues to ensure food safety [7,8].
In contrast, food additives are intentionally added to food to improve shelf life, flavour, texture or appearance [1,9]. Over 300 additives are authorised for use within the EU, each with specific conditions for use and maximum permitted concentrations as defined by the legislation [10,11].
Health effects from chemical contaminants are most often considered chronic, resulting from long-term, low-level exposure [2,12]. However, certain chemicals can cause acute illness with rapid symptom onset, depending on the amount or concentration of exposure [13]. Compared with biological agents, food-borne outbreaks caused by chemicals are less frequently reported [14]. Moreover, comprehensive EU data are lacking, as reporting of food-borne outbreaks to European Food Safety Authority (EFSA) does not include outbreaks caused by most chemical agents, except for biotoxins and microbial biogenic amines [15]. In Finland, food-borne and waterborne outbreaks caused by biological and chemical agents are reported by municipal authorities to the national Food- and Waterborne Outbreak (FWO) Registry.
Finland has a school meal programme, offering a daily school lunch free of charge to all students from preschool to upper secondary schools [16]. Participation in the school lunch is highest among younger students (aged 7–12 years), while older students eat the offered school lunch less frequently. School staff are allowed to purchase the school lunch. In many municipalities, meals are prepared in a central kitchen and distributed to satellite kitchens in schools.
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