Home canning is a popular and safe way to preserve food for later use. Jams, pickles, soups, sauces, meat and seafood are frequently canned in glass jars. If home canned foods are not properly prepared, they can cause serious illness such as botulism.
Botulism is caused by the toxin of bacterium – called Clostridium botulinum –that affects the nervous system and can cause paralysis.
It is estimated there are approximately 4 million cases of food-related illnesses of all types in Canada every year. Many of these illnesses could be prevented by following proper food handling and preparation techniques.
What you should do
The toxin that causes botulism is colourless, odourless, tasteless and invisible to the naked eye. You can prevent the toxin from forming in canned foods by following these tips:
Wash your hands using hot soapy water, and clean and sanitize all work surfaces, utensils and equipment. Keep them clean during all stages of the canning process. For a sanitizer, you can prepare a bleach solution by mixing 5 ml (1 tsp) of domestic bleach with 750 ml (3 cups) of water in a spray bottle. Spray surfaces and utensils, let it sit a minute and rinse with drinking water.
Use a pressure canner when canning low acid foods. A pressure canner is a large pressure cooker optimized for canning. Strictly follow the manufacturer’s instructions for canning foods considered to be low-acid, such as seafood, meats, vegetables and sauces. These low-acid foods must be processed in a pressure canner to destroy any Clostridium botulinum spores that might be present.
Foods such as fruit, pickles, jams, jellies, and marmalades will not support the growth of Clostridium botulinum due to their high acidity or high sugar content and can be safely processed in a boiling water canner. Make sure to follow the recipe. You cannot substitute sugar with pectin, as this will affect food safety. Pectin is often used to thicken foods such as jelly and jam.
Tomatoes are aborderline high-acid food and require an acid, such as lemon juice, citric acid or vinegar, to be added for safer canning.
Canning foods in their fresh state without added liquid is often not safe. The container should be topped up sufficiently with suitable liquid, such as syrup, sauce, brine or acidifying agent. When following tested recipes, do not substitute ingredients, change ingredient amounts or change the jar size that is in the recipe. Any modifications could lead to bacteria remaining in the food, and affect the safety.
Always follow the recommended recipes and processes along with the recommended temperature, time and pressure.
Each jar lid should be firmly sealed and concave (curved slightly inwards after cooling to room temperature). Before using stored foods – check that nothing has leaked from the jar, there are no unnatural odours and no liquid should spurt out when the jar is opened.
Clearly label your home-canned food, including the date it was canned. For best quality, use within one year from the date it was made.
Be sure to store your home-canned food in a cool, dry place. Once the container has been opened, refrigerate leftovers immediately.
Last words of wisdom
If you are buying or are given home canned products, ask about their preparation to help you to determine whether the proper safety steps were followed.
Always remember: never eat canned foods if you suspect the item has been tampered with, if the closure/seal has been broken, if the ends of the metal can or if the jar lid are swollen or leaking, or if the label is stained.