Noncompliance equals death seems to be turning into my tagline. Am I being over the top? Sadly not. According to the CDC, about 3000 people die from foodborne illness each year. That’s not counting the ones left serious/gravely ill. Which pathogens are most dangerous? For healthy adults, most pathogens will give a few days of discomfort (vomiting, diarrhea, fever). However, the response for at risk groups (young children, elderly adults, immunocompromised and pregnant individuals) is much more severe and more likely to be fatal. There are many food pathogens. The CDC has data showing which are more likely to cause illness, hospitalization, death. This is within the known causes of foodborne illness; more than 50% of cases remain unresolved.
In this post I am focusing on Clostridium botulinum. I was reminded of the horrors of botulism by a recent article in Gastro Obscura as this is a particularly unpleasant way to die. Fortunately C. botulinum doesn’t kill many people today because we know how to prevent it from growing and producing its toxin. Many food safety regulations are based around preventing C. botulinum from killing people.
C. botulinum is a problem in canned and bottled food because there is little or no oxygen present. The lack of oxygen reduces the chance of spoilage organisms but if we remove oxygen and C. botulinum will thrive. These bacteria are known as obligate anaerobes as they cannot survive if oxygen is present.
There are two types of heat treatment you can use to control C. botulinum, depending on whether your food is high in acid or not. C. botulinum does not like acid, so high acid foods can be boiled for a set time to kill the bacteria. Low acid foods, especially if they also are high moisture, must be heated to temperatures well above boiling. C. botulinum produces spores when under stress conditions that would kill other bacteria, such as Listeria or Salmonella spps. Spores are like the seeds for the bacteria and when conditions improve these spores germinate and release botulinum toxin, aka botox. Yes, the botulinum toxin which causes botulism is Botox and is used to remove wrinkles and helps a friend with her migraines..
To destroy C. botulinum and prevent spores in low acid food requires a temperature above boiling (>240 oF/116 oC; guide to temperatures and food preservation). This can be reached at home in a pressure canner. To show that food has been manufactured properly, temperature must be measured with a calibrated thermometer and records must be kept.
Processed food is divided into low acid and high acid food because C. botulinum cannot survive in high acid foods. People who make canned tomatoes and other mid-acid foods measure the acid content by measuring pH and reduce the pH so that the final product has a pH below 4.6 (more about pH and food). The acid level in food is measured as pH with a calibrated pH meter and records must be kept.
Reducing the water content can also reduce C. botulinum. Food technologists measure water activity (more about water activity) which is a more accurate measurement than moisture content of whether bacteria will grow in a food. To stop bacteria from growing, water activity should be below 0.85. This can be measured with a calibrated water activity meter and records must be kept.
In summary, while C. botulinum rarely causes foodborne illness, when it does it causes death. Therefore, the food entrepreneur must have constant vigilance to ensure that the food they are making is low acid, low moisture and/or heat treated and records to match their control method..
- Lydia Zuraw The 5 Most Dangerous Pathogens Food Safety News, Sept 14, 2015; Site last visited on Nov 26 2018.
- CDC Burden of Foodborne Illness: Findings; July 15, 2016; Site last visited on Nov 26 2018.
- CDC Home Canned Foods; October 4, 2018; Site last visited Nov 29 2018.
- CDC Botulism; October 4, 2018; Site last visited Nov 30 2018.
- FDA Guidance for Commercial Processors of Acidified & Low-Acid Canned Foods; March 14 2018; Site lasted visited Nov 30 2018.
- Tal Mcthenia The Lethal Lunch That Shook Scotland Atlas Obscura, Nov 15, 2018; site last visited Nov 30 2018.
- Julie A. Albrecht Clostridium botulinum University of Nebraska-Lincoln, no publication date; site last visited Nov 30 2018.
- Carolyn L. McCarty and co workers Notes from the Field: Large Outbreak of Botulism Associated with a Church Potluck Meal — Ohio, 2015; CDC MMWR, 64 (29); 802-803, July 31, 2015; site last visited Nov 30 2018.
- News Desk Ohio Botulism Outbreak: 1 Dead, 23 Hospitalized After Potluck Food Safety News, April 21 2015; site last visited Nov 29 2018
- National Center for Home Food Preservation, General Canning Information: Temperatures for food preservation Feb 2, 2017; Site last visited Nov 30 2018