Home canning safety
With the renewed popularity of seasonal, local eating, and the desire to be more environmentally friendly, many people are looking to home canning (also known as home bottling) to keep food for later use. While the food we eat in Canada is among the safest in the world, if home canned foods are not prepared or bottled properly they can cause botulism.
On this page:
Botulism is a serious and sometimes fatal illness you can get from eating improperly prepared, canned or bottled food. Botulism is caused by a toxin produced by the bacteria called Clostridium botulinum (C.botulinum). Botulism bacteria grow in a moist, oxygen-free environment so improper home canning and bottling can provide ideal conditions for it to multiply and produce the toxin.
Symptoms of botulism usually appear within 12 to 36 hours after eating the contaminated food. These symptoms may include:
- double vision
- dryness in the throat and nose
Serious health risks can include:
- respiratory failure
These symptoms will usually last two hours to 14 days but some can last longer. The groups at higher risk for serious health effects include pregnant women, children under the age of 5, adults over the age of 60, and people with weakened immune systems. You should see a health care professional and contact your local public health unit as soon as possible if you think you have botulism or food poisoning.
Botulism doesn't change the colour, odour or taste of food. When in doubt, throw it out!
Before you start canning
Foods for canning are classified into two types: high-acid foods and low-acid foods. Each type needs to be prepared differently to prevent the growth of harmful bacteria. Before you start canning, you need to determine the acid level of the food.
- High-acid foods (require a boiling water canner)
High-acid foods have a pH (acidity level) of less than 4.6. A boiling water canner heats food to 100°C (212°F) at sea level. The natural acid in the food will prevent botulism bacteria from growing and the heating will kill most yeasts, moulds and bacteria that could be present.
- Low-acid foods (require a pressure canner)
Low-acid foods have a pH (acidity level) of more than 4.6. Tomatoes are a borderline high-acid food and need an acid, such as lemon juice or vinegar, to be added for safer canning. Mixtures of low and high acid foods, such as spaghetti sauce with meat, vegetables and tomatoes, are considered low-acid foods. The level of temperature needed to kill botulism bacteria for low-acid foods can only be reached by using a pressure canner.
|High Acid Foods||Low Acid Foods|
|Fruit||Most fresh vegetables except tomatoes|
|Jams, jellies, marmalades||Meat, and poultry|
|Fruit butters||Seafood - fish and shellfish|
|Pickles and sauerkraut||Soup and milk|
|Tomatoes with added lemon juice or vinegar||Spaghetti sauce with meat, vegetables and tomatoes|
Home canning requires special equipment like glass jars, metal lids, metal rings, boiling water canners and pressure canners. There are many steps involved in home canning. If you have never done any canning before, it may be a good idea to take a home canning course, or read current books and magazines. It is important to follow current, tested practices for home canning.
Cleaning your hands, kitchen surfaces and utensils, fruit and vegetables will help eliminate bacteria and reduce the risk of food related illness.
- Wash your hands with soap and warm water for at least 20 seconds.
- Wash your fresh fruits and vegetables gently under cool, running, drinkable water before preparing and eating them.
- Use one cutting board for produce, and a separate one for raw meat, poultry, fish and seafood.
- Use paper towels to wipe kitchen surfaces, or change dishcloths daily to avoid the risk of cross-contamination and the spread of bacteria and avoid using sponges, as they are harder to keep bacteria-free.
- Sanitize countertops, cutting boards and utensils before and after preparing food. Use a kitchen sanitizer (following the directions on the container) or a bleach solution (5 ml household bleach to 750 ml of water), and rinse with water.
- Clean during all stages of the canning process to avoid cross-contamination.
Cooking food at high temperatures usually kills bacteria contained in your food. Home canning or bottling requires special attention because the botulism bacteria can grow when there is no oxygen. Follow the safety tips below to protect your family.
- Use a boiling water canner or a pressure canner according to the acidity of the food.
- Add an acid, such as lemon juice or vinegar, to some foods to help lower the pH and increase the acidity of the food.
- Never change the processing times or pressure levels. Substitutions can affect the time the canned or bottled food requires in the boiling water canner or pressure canner and can allow the botulism bacteria to remain in the finished canned or bottled product.
- Check from time to time that cooking or heating temperatures are maintained.
- Make sure the steam pressure is being maintained.
- Remember your process for each batch.
Safe equipment and recipes
- Only use proper jars for home canning or bottling.
- Only use new self-sealing lids and make sure the sealing compound is not damaged.
- Do not reuse old lids, even if they appear to be in good condition.
- Use only current, tested home canning recipes.
- Never substitute the jar size or the amounts of ingredients that are recommended in the recipe.
- Fill the jar leaving the recommended space at the top.
- Label and date all home canned foods before you store them.
- Store them in a cool, dry place.
- Once the container has been opened, refrigerate leftovers.
- Once a container containing seafood has been opened, refrigerate it immediately and throw it out no more than 3-4 days after opening.
- Use all canned or bottled foods within one year for best quality.
The bacterial spores that cause botulism are widespread in nature and commonly found in soil and dust. However, these spores rarely cause problems because they cannot grow if they are exposed to oxygen.
Buying canned or bottled products
Commercially canned products
The risk of getting botulism from commercially canned food is low because manufacturers use strict thermal processes designed to destroy botulism spores. However, avoid purchasing or using cans that are damaged or bulging. This could mean the contents are contaminated and may not be safe to eat.
Home canned products
Home canned foods are popular gifts year round. Make sure that the foods were home canned under strict food safety conditions. Never eat canned or bottled foods that are dented, leaking or have bulging ends, or if you suspect they have been tampered with. If in doubt, throw it out!
How the Government of Canada protects you
The Government of Canada is committed to food safety. Health Canada establishes regulations and standards relating to the safety and nutritional quality of foods sold in Canada. Through inspection and enforcement activities, the Canadian Food Inspection Agency (CFIA) verifies that food sold in Canada meets Health Canada's requirements.
- Date modified: