What you should know if you're home canning

Important information to protect your family and customers' health and safety

Home canning as a means of food preservation has been practised for generations. It is an excellent way of preserving the freshness of food products and increasing their conservation time.

However, if you are considering the use of home canning to process food for your own consumption or for sale or distribution to consumers, there are a number of things you need to know to ensure that your food products are safe to consume.

Given advances in scientific knowledge and some of the equipment used in home canning, it is essential to use recipes and processing instructions that are current and scientifically tested.

Failure to take proper precautions in the preparation of home canned foods can lead to botulism, a deadly form of food poisoning caused by the bacterium Clostridium botulinum. It can exist either as spores or as vegetative cells. Foods contaminated with C. botulinum toxin may not look or smell spoiled.

The spore is the dormant state of the bacteria and can exist under conditions where the vegetative cell cannot. Because the spores germinate only under anaerobic conditions (without oxygen), they are harmless on fresh foods. In fact, C. botulinum spores are present on most fresh food surfaces, and can survive in soil and water for several years.

The ideal environment for spore germination is:

  • a moist, low-acid food (pH > 4.6)
  • a temperature between 4° and 50°C (40° and 120°F), and
  • less than 2 per cent oxygen.

The spores are extremely heat-resistant and cannot be destroyed at boiling water temperatures. Temperatures well above 100°C (212°F) are needed to destroy them; thus all low-acid foods need to be processed at much higher temperatures, which are achieved through the use of a pressure canner.

Vegetative cells are produced by the spores when the right conditions exist. Vegetative cells multiply rapidly and produce a neurotoxin, a substance that is harmful to the human nervous system. Vegetative cells of C. botulinum are easily destroyed by heat.

Home canning is a great way to preserve food, as long as you take proper precautions to prevent botulism.

Image of several mason jars of home canned products

The bacteria and the spores do not grow in acid environments. Thus, acid foods (foods formulated to a pH of 4.6 or lower) can be processed in a water bath canner while low-acid foods (foods formulated to a pH >4.6) must be processed in a pressure canner.

Reliable sources of scientifically-validated home canning recipes and detailed processing instructions include the:

Caution: The preparation of home-canned products using recipes that have not been validated or deviating from a scientifically-validated recipe can have deadly consequences. If you process food from your home or community kitchen, note that:

  • Without any scientific testing, one cannot be certain as to whether the acidity of the recipe (pH) is sufficient, or how long the product actually needs to be processed to be safe.
  • Making substitutions to a validated recipe, such as decreasing the amount of vinegar or increasing the amount of vegetables can create a product that is low acid and thus could result in botulism poisoning if processed as an acid food.
  • Adjustments to the amount of starch or other thickening agents in a recipe will change the rate of heat penetration into the product and could lead to under-processing.

Remember: There are many validated recipes and processing instructions available to help you prepare safe home canned products and avoid unnecessary risks. Protect your food from spoilage and your family and consumers from serious food poisoning by following scientifically-tested processes and recipes.

For more information on botulism and canned foods commonly associated with it, visit the Government of Canada Healthy Canadians website at www.healthycanadians.gc.ca/eating-nutrition/poisoning-intoxication/botulism-botulisme-eng.php


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: Paul Bailey, Risk Identification & Management Coordinator/OMAFRA
Creation Date: 08 September 2011
Last Reviewed: 26 February 2015