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Food Safety Tips for Home Canning
With the renewed popularity of seasonal, local eating, and the desire to be more environmentally sustainable, many people are looking to home canning (also known as home bottling) to preserve food for later use. However, if home canned foods are not properly prepared, they can cause serious illness such as botulism.
Botulism
Botulism is a serious and sometimes fatal illness that can result from eating improperly prepared, canned or heat-processed bottled food. Botulism is caused by a bacterium - called Clostridium botulinum - that naturally produces toxins as part of its normal life cycle.
The bacteria and toxin that cause botulism are invisible to the naked eye and do not change the colour, odour or taste of food. They are not necessarily destroyed by cooking, so preventing the toxin from forming is essential.
C. botulinum has a protective structure called a spore. Destroying the spores takes a higher temperature than boiling. If the heating process is not extensive enough or if the food is not acidic while you are home canning and bottling, the botulism bacteria can grow and produce toxins.
Risk for botulism
All people are at risk for botulism. Symptoms of botulism range from nausea, vomiting, fatigue, dizziness, headache, double vision and dryness in the throat and nose, to respiratory failure, paralysis and, in some cases, death. The onset of symptoms is generally from 12 to 36 hours after ingesting the toxin. The duration of illness may be 2 hours to 14 days, while some symptoms may stay longer. Every year in North America, people get sick from botulism after eating home-canned food that was not properly prepared.
Food safety risks to home canning
The bacteria, Clostridium botulinum, and its toxin, are very heat-resistant and can remain in foods cooked at high temperatures. As the bacteria can grow in a moist, oxygen-free environment, home canned or home bottled foods provide the perfect conditions for the bacteria to grow and produce the toxin if not prepared properly. The food must therefore be adequately canned and heat-processed.
The altitude where you live is another factor you should take into consideration when home canning or bottling foods. At sea level, water boils at 100°C (212°F). As altitude increases, water boils at lower temperatures. Since lower temperatures would be less effective in killing bacteria, you would need to increase the processing time as altitude increases.
The food safety tips provided are intended for individuals who are home canning for their own private use.
Before you start canning
Home canning requires special equipment, such as glass jars, metal lids, metal rings, boiling water canners and pressure canners. 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 on home canning.
Foods for canning are classified into two types: high-acid foods and low-acid foods and before you start canning, you need to determine the acid level of the food. Each type of food requires a different method of heat processing to achieve the required temperatures necessary to prevent the growth of harmful bacteria. You therefore need to use a boiling water canner for high-acid foods and a pressure canner for low-acid foods.
- High-acid foods (require a boiling water canner)
High-acid foods include those with a pH of less than 4.6, such as fruit, pickles, sauerkraut, jams, jellies, marmalades and fruit butters. A boiling water canner heats food to 100°C (212°F) at sea level. The acid in the food prevents bacteria from growing, while this temperature will kill most yeasts, moulds and bacteria that could be present. As the bacteria that causes botulism does not grow at a pH below 4.6, it is not a concern for high acid foods. - Low-acid foods (require a pressure canner)
Low-acid foods include those with a pH of more than 4.6, such as meat, seafood, poultry, soup, milk and most fresh vegetables, except tomatoes. Tomatoes are borderline high-acid food and require 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. For low-acid foods, the required temperatures can only be achieved in a pressure canner to destroy the bacteria which cause botulism.
A boiling water canner is sometimes called a"boiling water bath". It is a large pot with a fitted lid and is usually made of aluminum or porcelain covered steel. It also comes with removable racks for resting the jars.
A pressure canner is a vessel especially designed to treat canned foods. Pressure canners use steam under high pressure to ensure that the low-acid food reaches the high temperatures necessary to eliminate the bacteria that causes botulism. These high temperatures can only be reached with a pressure canner. A pressure canner is not the same as a pressure cooker. A pressure canner usually has a locking lid and comes with a jar rack, a pressure gauge and a steam vent. The pressure gauge must be checked each year to ensure the food is treated at the right pressure. Always follow the instruction manual that came with the pressure canner. If you have a pressure canner without an instruction manual, contact the manufacturer to get a replacement copy.
Home Canning Practices
There are many practices involved in home canning. It is important to follow current, tested practices for home canning:
Cleaning and Sanitizing
- Wash your hands for at least 20 seconds with soap and warm water.
- Wash raw fruits and vegetables thoroughly with clean, running water before you prepare and eat them, because they can also be contaminated with bacteria, viruses and parasites.
- Clean and sanitize all work surfaces, utensils, and equipment and keep them clean during all stages of the canning process to avoid cross-contamination.
Equipment
- Use the proper jars for home canning or bottling.
- Only use new self-sealing lids and make sure the sealing compound is not damaged before you use them.
- Do not reuse old lids. Although the sealing compound of used lids may appear to be in good condition, the seal made with reused lids may become inadequate.
Current recipes
- Use only current, tested home canning recipes:
- Never substitute the jar size or the amounts of ingredients that are recommended in the recipe. Substitutions can affect the time the canned or bottled food requires in the boiling water canner or pressure canner and can cause the botulism bacteria to remain in the finished canned or bottled product.
- Never change the recommended processing times or pressure levels
- Fill the jar leaving the recommended space at the top according to the recipe.
- Use the appropriate heat-processing method 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.
- During the processing operation:
- Check from time to time that adequate cooking or heating temperatures are maintained.
- Make sure the steam pressure is being maintained as well.
Storing
- Label and date all home canned foods before you store them.
- Store them in a cool, dry place. For best quality, use within one year from the date they were made.
Buying canned or bottled products
Commercially canned products
- The risk of botulism from commercially canned food is low, as manufacturers use strict thermal processes designed to destroy the spores of C. botulinum. However, avoid purchasing or using cans that are damaged or bulging, as this could indicate that the contents may not be safe to eat.
Home Canned products
- As 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. When in doubt, throw it out!
Foodborne illness
If you think something you ate made you sick, seek medical treatment right away. If diagnosed early, botulism is treatable, although a complete recovery may take a long time.
What the Government of Canada does to keep our food supply safe
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 verifies that food sold in Canada meets Health Canada's requirements.
For more information on food safety, please visit the 
Government of Canada's Food Safety Portal and the Canadian Partnership for Consumer Food Safety Education's Be Food Safe Canada program.
