By Marisa Bunning and Elisa Shackelton, CSU Extension Specialists, Department of Food Science and Human Nutrition
Most cooks tend to be a bit creative – they aren’t afraid to try new things, and that’s part of the fun. But home food preservation, especially canning, requires following specific safety procedures that are more like commercial food production than home cooking. With so many people trying their hand at canning for the first time, it is especially important that new Colorado preservers understand the importance of making the necessary time or pressure adjustments for their home’s elevation (also referred to as ‘high altitude’).
Home canning can be dangerous if tested recipes and processing instructions are not followed. This is especially true in Colorado where adjustments to canning recipes (that are often developed and tested at sea level) are a critical food safety step for people living in high elevation communities.
Not commonly known is that Colorado and other western states have higher per capita rates of foodborne botulism than other parts of the United States.
One contributing factor is that the soil in the western U.S. from the Rocky Mountains to the Pacific Ocean contains a particularly high count of Type A Clostridium botulinum spores, the type of spores that produce the toxin most dangerous to humans.
A second factor is the higher altitude.
- Boiling water canning instructions require additional time at higher elevation because water boils at lower temperatures than the ‘standard’ 212°F at sea level.
- Foods that are low in acid, like beans or carrots, must be heated in a pressure canner to achieve a temperature of 240°F to deactivate Clostridium botulinum spores, and prevent the formation of the botulism toxin.
Foodborne botulism is often misdiagnosed.
- Symptoms usually appear within 18 to 36 hours after the contaminated food is eaten, but the time can vary from six hours to 10 days. The most significant symptoms are blurred double vision and difficulty in swallowing and speaking.
- For some types of the disease, early symptoms may be gastrointestinal (nausea, vomiting, abdominal pain, constipation, cramps, headache, fullness) and lead to a false diagnosis of appendicitis, bowel obstruction or heart attack.
Preserve Smart Colorado
Following high elevation adjustments and using tested recipes ensures crucial temperature and time requirements are achieved to destroy Clostridium spores within canning jars. Unfortunately, many canning recipes found in magazines, newspapers, old cookbooks, or those handed down from family members do not include high elevation adjustments.
Land grant university-based Extension offices across the U.S. are the most reliable ‘go-to’ resource for home canning questions, but all too often questions come in after the food has already been canned and involve issues that deem the food unsafe to consume. A free app developed by Colorado State University Extension, called ‘Preserve Smart,’ helps users determine and input their kitchen elevation so that the processing instructions for each recipe (for over 55 fruits and vegetables) are automatically highlighted for that elevation.
Tips for canning safely at home
Use up-to-date, scientifically-tested home canning recipes.
- Read through the recipe ahead of time to make sure you have the necessary ingredients, supplies, equipment, and the time it will take for the entire process.
- Use tested recipes from the National Center for Home Food Preservation and your state’s Extension service.
- Err on the side of caution and avoid using home canning recipes from untested sources.
- Freezing and drying can be great alternatives to home canning, especially for those that live at very high elevations where safe home canning cannot be assured.
Follow the recipe and instructions exactly and make the recommended processing adjustments are for your home’s elevation.
- Determine your home’s elevation by using a resource such as https://whatismyelevation.com/
- Contact your local Extension office before you start canning if unsure of the processing instructions.
- Use the recommended equipment for the type of food you are canning (i.e., always use a pressure canner to process low-acid foods)
Did you know?
- The CDC reports that five western states (Colorado, California, Washington, Oregon and Alaska), accounted for more than half of all reported foodborne outbreaks of botulism since 1950.
- Home-canned vegetables are the most common cause of botulism outbreaks in the U.S.
For more information, refer to the CSU Extension website or use the free Preserve Smart app, which recently won the First Place National Food Safety Award from the National Extension Association of Family and Consumer Sciences.