Home Canning and Botulism
Home canning is an excellent way to preserve garden produce and share it with family and friends, but it can be risky or even deadly if not done correctly and safely.
It's summer, and home gardeners are harvesting the delicious produce they've been growing. Home canning is a great way to preserve your garden goodies. But beware: if it's done the wrong way, the vegetables you worked so hard for could become contaminated by a germ that causes botulism, a serious illness that can affect your nerves, paralyze you, and even cause death. Read on to learn about the safe way to can so you can protect yourself, your family, and others when you share your home-canned goodies.
Don’t let your canned veggies spoil
Follow these two tips to keep your canned vegetables safe and keep them from spoiling.
1. Use proper canning techniques.
Make sure your food preservation information is always current with up-to-date, scientifically tested guidelines. Don't use outdated publications or cookbooks, even if they were handed down to you from trusted family cooks.
You can find in-depth, step-by-step directions from the following sources:
- The National Center for Home Food Preservation
- USDA Complete Guide to Home Canning
- The state and county extension service of your state university
2. Use the right equipment for the kind of foods that you are canning.
Always use a properly sized pressure canner that meets USDA recommendations for pressure canning [3.61 MB] when canning low-acid vegetables (like green beans, potatoes and corn), meat, seafood and poultry. Contact your local Cooperative Extension Service office to find out if your pressure canner is recommended. Pressure canning is the only recommended method for canning low-acid foods. Do not use boiling water canners for low-acid foods because they will not protect against botulism poisoning.
Low-acid foods have pH values higher than 4.6. They include red meats, seafood, poultry, milk and all fresh vegetables except for most tomatoes. To check whether a food is low-acid, see this FDA list of pH values for foods.
Make your home-canned vegetables safe
- Use a recommended pressure canner that holds at least four one-quart jars sitting upright on the rack.
- Be sure the gauge of the pressure canner is accurate.
- Clean lid gaskets and other parts according to the manufacturer’s directions.
- Vent the pressure canner before pressurizing and follow recommended cooling steps.
- Use up-to-date process times and pressures for the kind of food, the size of jar, and the method of packing food in the jar.
What is botulism?
Botulism is a rare, but serious illness caused by a germ called Clostridium botulinum. The germ is found in soil and can survive, grow, and produce toxin in a sealed jar of food. This toxin can affect your nerves, paralyze you, and even cause death. Even taking a small taste of food containing this toxin can be deadly.
Botulism is a medical emergency. If you have symptoms of foodborne botulism, seek medical care immediately.
Symptoms may include the following:
- Double vision
- Blurred vision
- Drooping eyelids
- Slurred speech
- Difficulty swallowing
- Dry mouth
- Muscle weakness
Protect yourself from botulism: When in doubt, throw it out!
- Home-canned foods could be contaminated but look, smell and taste normal.
- If there is any doubt about whether safe canning guidelines have been followed, do not eat the food.
- Home-canned food might be contaminated if:
- The container is leaking, bulging, or swollen
- The container looks damaged, cracked, or abnormal
- The container spurts liquid or foam when opened
- The food is discolored, moldy, or smells bad
Use proper canning techniques and equipment to make sure your canned vegetables are safe.
- If you suspect home-canned food might be contaminated with the germs that cause botulism, throw the food away.
If any of the food spills, wipe up the spill using a recommended bleach solution (1/4 cup unscented bleach for each 2 cups of water).
- Never taste home-canned food to determine if it is safe. Do not taste or eat foods from containers that are leaking, have bulges or are swollen, or look damaged, cracked, or abnormal.
- When you open a jar of home-canned food, thoroughly inspect the food. Do not taste or eat foods that are discolored, moldy, or smell bad. Do not eat food from a can that spurted liquid or foamed when it was opened.
- Do not open or puncture any unopened cans, commercial or home-canned, if you suspect contamination.
Outbreaks and Home-Canned Vegetables
Home-canned vegetables are the most common cause of botulism outbreaks in the United States. From 1996 to 2014, there were 210 outbreaks of foodborne botulism reported to CDC. Of the 145 outbreaks that were caused by home-prepared foods, 43 outbreaks, or 30%, were from home-canned vegetables. These outbreaks often occur because home canners did not follow canning instructions, did not use pressure canners, ignored signs of food spoilage, or were unaware of the risk of botulism from improperly preserving vegetables.s
For more information, see:
- General information about botulism (Clostridium botulinum)
- Botulism at FoodSafety.gov
- Foodborne Germs and Illness
- Medscape commentary: Botulism: Countering Common Clinical Misperceptions
More Resources on Home Canning
Recent Scientific Articles about Botulism
- Botulism Associated with Home-Fermented Tofu in Two Chinese Immigrants — New York City, March–April 2012
- Notes from the Field: Botulism From Drinking Prison-Made Illicit Alcohol – Arizona, 2012.
- Three outbreaks of foodborne botulism caused by unsafe home canning of vegetables--Ohio and Washington, 2008 and 2009
- Page last reviewed: June 13, 2016
- Page last updated: June 13, 2016
- Content source:
- National Center for Emerging and Zoonotic Infectious Diseases
- Page maintained by: Office of the Associate Director for Communication, Digital Media Branch, Division of Public Affairs