Many gardens are already seeing a bountiful crop with the rains and cooler spring weather. When the garden is providing an abundance of produce, home canning is a great way to enjoy that summer garden into the winter months.
Fresh garden produce spoils due to bacteria, molds and yeast, food enzymes and contact with the air. Microorganisms live and multiply quickly on the surface of fresh foods and inside bruised and insect-damaged produce. Proper canning will stop the growth and activity of microorganisms and help prevent spoilage and loss of quality.
The canning process involves placing foods in jars and heating the product to a temperature that inactivates enzymes and destroys microorganisms that can cause food to spoil. Air is driven from the jar during the heating process and as it cools, a vacuum seal is formed between the lid and the jar that prevents air from getting back into the product and contaminating the food.
To get the best results when canning you should select and wash quality fresh food that is free from bruising, insect damage and disease. Inspect any fruits and vegetables that you harvest from your own garden or purchase at a farmers’ market. Only the highest quality of produce should be used.
There are three safe ways of canning; these are the boiling-water canner method, the steam canner method and the pressure canner method. The recommended method depends on the acidity level of the food being canned.
Highly acidic foods such as fruits, tomatoes, salsa, pickles and sweet spreads, should be canned using either the boiling water canner or the steam canner method. Low-acid foods, such as vegetables, meats, poultry and fish must be canned using a pressure canner. To prevent food-borne illness when canning high acid and low acid foods, you must carefully follow research-based methods and recipes.
The boiling-water and steam canner methods are recommended for safely canning high-acid foods, such as fruits, tomatoes, salsa, pickles and sweet spreads. In these methods, jars of food are heated to 212° F by being fully immersed by boiling water or steam.
Pressure canning is the only safe and recommended method of canning low-acid foods, such as vegetables, meats, poultry and fish. In this method, using 2 to 3 inches of water within the pressure canner, jars of food are heated to at least 240° F. This temperature can only be reached in a pressure canner. You must process low-acid foods, such as vegetables, meat, poultry and fish, in a pressure canner to prevent botulism, an often-fatal type of foodborne illness.
Clostridium botulinum, a common soil bacterium that causes botulism food poisoning, is destroyed in low-acid foods when they are processed at the correct time and temperature in pressure canners. Never use a boiling water or steam canner for low-acid foods because botulinum bacteria can survive this process. If Clostridium botulinum bacteria survive and grow inside a sealed jar of food, they can produce a deadly toxin. Even a taste of food containing this toxin can be fatal. Improperly canned low-acid foods may contain the toxin that causes botulism without showing signs of spoilage. Low acid and tomato foods not canned according to USDA-endorsed recommendations present the highest risk of botulism.
POINTS TO REMEMBER
• Low-acid food are to be processed in a pressure canner.
• High acid or acidified foods are to be processed in a boiling water or steam canner.
• Processing time & pressure should be adjusted for your elevation.
• Processing time & pressure matches the size of jar, style of pack and type of food being canned.
• Use recommended jars and self-sealing, two piece lids.
Many state extensions offer classes and guides to help you get started with the basics and provide tested recipes. Check with your local extension if they offer pressure canner testing. For a thorough, free database of tested recipes and beginner tutorials, you can also refer to the National Center for Home Food Preservation.
