Introduction to basic canning techniques

Canning is a method of preserving food in jars for use long after the growing season has ended. Canning saves money and provides higher quality food products for families. When food is preserved by canning at the peak of freshness, flavor, color and nutrients are maintained. There are two safe research-based techniques for canning. One is the boiling water bath method and the other is pressure canning.

Boiling water bath canning

Water bath canning is used for foods that are considered high acid. Those foods include fruits like peaches, apples, and berries. Pickles are another high acid food since they are canned in vinegary brine. Tomatoes may also be canned by using the boiling water bath method if they are acidified first. Acidification can be done by adding two tablespoons of bottled lemon juice to each quart of tomatoes or one tablespoon per pint. Jellies and Jams are also high acid products that may be canned use the boiling water bath method.

A boiling water bath is accomplished by filling a large pot with water and bringing it to simmer. Once jars are filled with food and hot liquid, the jars are placed on top of a rack inside of the pot or canner. The water should cover the tops of the lid by one to two inches. After covering the pot with a lid, the water is allowed to come to a boil, after which the jars are processed for an amount of time specified for the type of food being canned and the size of jar being used (half-pints, pints, or quarts, etc.). Once the jars have processed for the time period indicated, they are removed and placed on a kitchen towel on a counter to cool. A sing of a jar that has sealed is a ping-like sound. A seal indicates that a vacuum has been created in the jar.

The temperature in a water bath canner reaches 212 degrees Fahrenheit. This temperature is hot enough to kill pathogens that could cause high acid foods to spoil. Additionally, the acid in the product is another safeguard against harmful bacteria or other pathogens that could make food unsafe to eat.

Pressure Canning

Pressure canning is the method of canning that is used to preserve low acid foods like green beans, corn, okra, greens, potatoes and meats. Low acid foods are those that have little to no natural acid or are not processed using an acid like vinegar. Low acid foods are susceptible to a bacterium known as clostridium botulinum. This bacteria causes botulism, a potentially deadly foodborne illness. This pathogen is found in soil and thrives in anaerobic or oxygen free environments like jars and cans of food. To reduce the likelihood that home canned food will be affected by this bacteria, a pressure canner must be used for processing.

Clostridium botulinum is a spore forming bacteria which means that when heated to high temperatures it can form a protective outer shell that allows it to rejuvenate and thrive when the conditions are right. To kill this pathogen the home canned product must reach a temperature of 240 degrees F for a specified period of time. This can only be accomplished with a pressure canner. When food is processed in a pressure canner. Jars are filled and after lids and rings are placed on them, the jars are placed in a pressure canner on a rack in two to three inches of simmering water. The lid on the canner is locked into placed and the canner is heated. Steam should be allowed to escape from the canner vent pipe for at least 10 minutes to drive air from the canner. Once this is achieved a weight is placed over a vent pipe to allow pressure and temperature to build inside of the canner. Food is processed for a specified period depending upon information provided in the pressure canner manual or in a research-based canning guide.