HOME CANNING SAFELY - High vs. Low Acid Foods

With the renewed interest in food security, we are seeing a desire for people right across the North Cariboo looking to home canning, including pressure canning, as a way of preserving food for later use.  

The Government of Canada has some good information online that reviews some of the things one should consider before home canning.  To begin with, foods are classified into 2 types: high-acid foods and low-acid foods.  Each type needs to be prepared differently to prevent the growth of harmful bacteria. Before you start canning, you need to determine the acid level of the food.

• High-acid foods (require a boiling water canner)
  High-acid foods have a pH (acidity level) of less than 4.6. A boiling water canner heats food to 100°C (212°F) at sea level. The natural acid in the food will prevent botulism bacteria from growing and the heating will kill most yeasts, moulds and bacteria that could be present.

• Low-acid foods (require a pressure canner)
  Low-acid foods have a pH (acidity level) of more than 4.6. Tomatoes are a borderline high-acid food and need 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. The level of temperature needed to kill botulism bacteria for low-acid foods can only be reached by using a pressure canner.

Examples of High vs. Low Acid Foods

High Acid Foods	Low Acid Foods
Fruit	Most fresh vegetables except tomatoes
Jams, jellies, marmalades	Meat, and poultry
Fruit butters	Seafood - fish and shellfish
Pickles and sauerkraut	Soup and milk
Tomatoes with added lemon juice or vinegar	Spaghetti sauce with meat, vegetables and tomatoes

Check out this site for additional safety information.