Home canning

Canning is an excellent way to enjoy fruits and vegetables all year long. It also contributes to a varied and balanced diet.   

Canning is also a good way to reduce food waste at home because foods like wilted fruits and vegetables can still be used.  

Canning is a highly effective storage method. However, you must follow all instructions carefully and choose the right equipment. Improper techniques can pose health risks.  

In the canning process, food and containers must be heated to very high temperatures. Each recipe has a different processing time to ensure that all microorganisms that could cause food poisoning are eliminated. 

Clostridium botulinum bacteria are widespread in nature and heat resistant. In favourable conditions, these bacteria can grow and produce a toxin that causes botulism, a serious type of food poisoning. Food contaminated by these bacteria may show no signs of spoilage. 

One of two safe sterilization methods must be used to destroy microorganisms, depending on the acidity of the food being canned. 

Boiling water sterilization 

Foods with a pH of 4.6 or lower, such as raspberries, apples, strawberries, blueberries, fruit marmalade and jam, are naturally protected against the growth of Clostridium botulinum. 

This means that boiling water is enough to avoid food spoilage such as mould. 

While tomatoes are naturally acidic, their pH varies depending on the tomato variety, growing conditions and time of harvest. This variability means that tomatoes do not always reach the target pH of 4.6 or lower. An acidifying agent like lemon juice must be added to tomato-based products in order for this sterilization method to be safe. 

Pressure sterilization 

A pressure canner is a pot that comes with a pressure lid. 

Low-acid foods with a pH higher than 4.6—such as peppers, carrots, cabbage, asparagus, meat and spaghetti sauce—must be sterilized at 116°C (240°F) to destroy Clostridium botulinum bacteria. 

Only a pressure canner can destroy bacteria by reaching the safe temperature of 116°C (240°F) at 70 kPa (10 lb.) of pressure. 

For each type of food, preparation method and format, carefully follow the recommendations in canning reference guides or the user guides that come with your equipment. These recommendations cover the required headspace, procedures, timing and temperatures. Every detail counts.  

Some domestic pressure cooker models (Cocotte-Minute or Presto) can use heat and pressure to can low-acid foods. However, most of these devices are designed for cooking, not sterilization. Be sure to find out more when purchasing a device and read the user guide carefully.  

Thickeners 

Ingredients like flour and cornstarch tend to slow the penetration of heat into the food, which can lead to underprocessing. Avoid adding them to your recipes.  

Here’s what you should check when it’s time to eat home-canned foods: 

• Before opening a jar, carefully examine it to identify any signs of spoilage.  
• Check the contents for any unpleasant smells. Do not taste any food that looks unusual, is foaming or smells bad.   
• When in doubt, throw it out!