EatRight Ontario Print Header

Get answers to your nutrition and healthy eating questions. Visit or call us toll-free at 1-877-510-510-2.

Get answers to your nutrition & healthy eating questions.

Call us toll-free† at
1-877-510-510-2 to speak directly with a Registered Dietitian.

Home Canning FAQs

What foods are best for home canning?

Almost all foods can be home canned. The most popular foods for home canning include fruits and tomatoes, as well as preserves like chutneys, jams, jellies, pickles and relishes. It is also possible to can fresh vegetables, meat, milk, poultry, fish and prepared foods such as soups and stews.

Foods for home canning are organized by their acid level. Before you start home canning, you need to know whether a food is a “high-acid” food or a “low-acid” food.

  • Low-acid foods include: meat, seafood, poultry, milk and fresh vegetables except tomatoes*
  • High-acid foods include: fruits, pickles, sauerkraut, jams, jellies, marmalades and fruit butters.

*Tomatoes are a borderline high-acid food. When tomatoes are being prepared for canning, an acid (such as vinegar) must be added to them to make them safer for preserving.

Why do I need to know the acid level of the food?

The acid level of a food will affect the home canning method that you use. Foods that are high-acid should be canned with a boiling-water canner. With this method the acid in the food prevents bacteria from growing, while the high temperature will kill any bacteria that are present. 

Foods that are low-acid must be canned with a pressure-canner.    A pressure canner reaches higher temperatures. Because these foods don’t have natural acid, you will need higher temperatures to kill the bacteria (such as the botulism spores). These temperatures can only be reached with a pressure canner.

  • Boiling-water canner: This is sometimes called a “boiling water bath”. It is a large pot made of aluminum or porcelain covered steel. It comes with removable racks (for resting the jars) and a fitted lid. 
  • Pressure canner: This is an aluminum pot with a locking lid. It comes with a jar rack, pressure gauge and a steam vent. The pressure gauge must be checked every year to make sure that the canner is working at the right pressure. The pressure creates steam that raises the temperature of the pot so that low-acid foods can be preserved safely. *Pressure canners are not the same as pressure cookers.

What equipment do I need to get started?

  • Proper canning jars made of special tempered glass that can withstand sterilization and high hot water temperatures. 
  • A jar lifter or jar rack for placing your jars in and out of the boiling-water canner.
  • A small spatula to get rid of air bubbles when processing the food.
  • A wide-mouth funnel to avoid spilling food.
  • A boiling water canner for high acid foods. You can make your own boiling water canner or purchase one. To make your own: You will need a deep pot with a tight fitting lid. The pot should be able to hold the canning jars with extra space for 3-5 centimetres (1-2 inches) of water. A cake rack can be used for resting the jars on the bottom of the pot.
  • A pressure canner for low acid foods. Always check to make sure that your pressure canner is in good working order. Follow the instruction manual that came with your pressure canner. If you have a pressure canner without an instruction manual, contact the manufacturer to get a replacement copy.
  • A tested recipe. Tested recipes have the right amount of acid and moisture to keep your foods safe. Never change a recipe on your own as this can change the environment and make it easier for bacteria to grow.

What methods of canning and equipment are not recommended?

Some of these canning methods and equipment used to be popular but they are no longer thought to be safe:

  • Open kettle canning.
  • Processing freshly filled jars in conventional ovens, microwave ovens and dishwashers.
  • Steam canners.
  • Jars with wire bails and glass caps. Use only glass or metal jars with self-sealing lids.
  • Paraffin wax sealing.
  • Zinc porcelain lined caps.
  • While you many reuse canning jars, you should always use a new lid.
  • Do not use commercial jars such as those for mayonnaise or salad dressings as they are not designed for home canning.

Once I have filled the jars with food how long should they be boiled for to be safe?

The boiling time will depend on:

  • The canning method. Foods cooked in a pressure canner take longer than those cooked in a boiling water canner.
  • The type of food. High-acid foods can be processed faster than low-acid foods.
  • The amount of food packed into the jar.
  • The type and size of the jar.
  • The altitude. If you live at a high altitude, the processing of canned foods takes longer and even the pressure you will need to use may be different. 

*Always follow the recipe instructions. Each recipe will have a processing time based on the type and quantity of ingredients being used.

How do I know if my jars have sealed properly?

Remove the metal screw bands on the jars and try these tests:

  1. Press the middle of the lid with your finger. If the lid springs back up, it is not sealed. 
  2. Tap the lid with the bottom of a teaspoon. If you hear a dull sound, it is not sealed properly. A properly sealed jar makes a ringing, high-pitched noise. 
  3. Hold the jar at eye-level. A flat or bulging lid means it has not sealed properly. A properly sealed lid should dip down slightly in the centre. 

If the jar has not sealed properly, you can:

  • Boil the jar again using the same cooking time. Check to make sure the jar and lid have no nicks or cracks.
  • Freeze the food for later use.
  • Store in the fridge and eat within a few days.

How long can I store my canned foods?

Home canned foods should be eaten within one year. Label and date your foods after canning so you know by when you should use them. 

I’m worried that my food may have spoiled. What should I do?

Foods that have botulism do not always look or smell spoiled. Do not taste any food that you think may have spoiled. If your food has foamed, smells “bad” while cooking, or the container has a bulging lid, throw it out right away. Place the jar and its contents in a waterproof container and place in the garbage. Wash your hands, equipment, utensils and work surfaces with warm soapy water.


Here you'll find more information on this topic: Home Canning


For step by step instructions on home canning:

National Centre for Home Food Preservation


Copyright © Dietitians of Canada 2015. All rights reserved.

Dietitians of Canada acknowledges the financial support of EatRight Ontario by the Ontario government. The views expressed do not necessarily reflect those of the Province.