Canning Basics
Concepts and Terms

Canning Basics - The Process

To understand canning basics, you need to know that it is a process that preserves food for long term storage at room temperature by accomplishing three things:

1 - Canning destroys the microorganism that are naturally in and on food. It stops food from spoiling and making you sick. This is done by applying heat to the food, killing bacteria, yeasts, molds and their spores.

2 - Heating also destroys enzymes that cause food to start to decompose or loose it's flavor. That's why you should always get the freshest fruit and vegetables possible for canning and freezing.

3 - Canning seals the container so that after all those bad critters are killed off, more of them can't get in later.

When a canning jar is heated, the air inside (called headspace) expands. Some of that air is forced out around the lid. Since you put the lid on firmly before canning, the rubber compound on the inside of the lid is in full contact with the jar rim and creates a seal. As the jar cools down, the air inside contracts, causing a partial vacuum inside.

That's the reason chipped jars should NEVER be used, and you should always wipe the rims of the jars clean before applying lids and rings. It's also a good idea to inspect the rubber compound inside the lids before using them to make sure that none are damaged or deformed. Any of these things could cause a jar not to seal.

Canning Basics - Definitions

Pressure Canning - Canning process that involves placing filled canning jars in to a sealed vessel (pressure canner),to increase pressure inside, which in turn increases temperature. This method is used for low acid foods, because the microorganisms that exist inside low acid foods require highertemperatures to destroy them.

Boiling Water Canning - Also known as hot water bath canning. This process involves placing filled canning jars in a bath of boiling water without additional pressure. This method is used for high acid foods.

High Acid Foods - Foods that have a pH of about 4.5 or less. Most fruit, and a few vegetables fall into this category.

Low Acid Foods - Foods that have a pH of greater than about 4.5. Most vegetables, and all meats, including poultry and seafood, fall into this category.

pH - A scale used by chemists to measure the presence or absence of acid. The range of the scale is 0 to 14. Anything below 7 is considered acidic. Anything above 7 is considered basic or alkaline. A pH reading of 7 is neutral. For what it's worth pH stands for "potential of Hydrogen".

Headspace - The gap of air in a canning jar between the top of the food, and the top of the jar. Headspace is what allows the canning jars to seal. The correct amount of headspace is important. Make sure you follow instructions about correct headspace when canning.

Hot Pack - Packing food in jars for canning that has already been cooked, at least partially.

Raw Pack - Packing raw food in jars for canning. Vegetables and some fruit can be raw packed. This is also known as cold pack canning.

Blanching - Placing raw fruit or vegetables in boiling water for a brief period of time. This is NOT cooking. Blanching serves two purposes.

Blanching loosens the skin on some fruit and vegetables to make it easier to remove the skin. Examples of foods that are blanched to remove the skin are tomatoes and peaches.

Blanching is also done to destroy enzyme activity. This is primarily done when preparing food for freezing. A good example of food that is blanched to destroy enzymes for freezing would be sweet corn.

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