(Editor's Note: This article was originally published on August 24, 2007. Your comments are welcome, but please be aware that authors of previously published articles may not be able to promptly respond to new questions or comments.)
The French government offered a reward of 12,000 francs to anyone who could come up with a method to preserve food.
Nicholas Appert, a candy maker had a theory that if food was sealed into an airtight container and sufficient heat was applied, foods should not spoil. After 14 years of experimentation Appert won the 12,000 francs. Canning as we know it today was born.
Appert packed foods into bottles, corked them and submerged them into boiling water. Without realizing how it worked the heat killed the bacteria that caused food to spoil.
Water Bath Canning
This technique is used to can foods that have an acidity or pH level of 4.6 or lower. Some examples of foods that can be preserved by water bath canning are pickles, relishes, jams, butters, fruit preserves and acidified tomatoes.
As we all know water boils at 212 degrees F at sea level. This temperature is high enough to kill bacteria, yeasts, and molds that cause food spoilage.
Foods that can be processed on this manner are processed in a water bath canner. It consists of 3 parts: A base large enough to hold the jars being processed with at least 2 inches of water covering the tops of the jars. A rack holding the jars to keep them off the bottom of the canner, and a lid that helps keep the water boiling during the processing.
Water Bath Canner
In order to kill bacteria and mold in low acid foods, a temperature of 240 degrees F must be attained. In order to reach temperatures that high; water must be heated under pressure. This is done in home canning by using a pressure canner.
A pressure canner consists of 4 parts:
A base deep enough to hold the size jars being processed without obstructing the locking lid.
A rack on which the jars sit off the bottom of the base and allow steam to circulate around the jars.
The lid which is equipped with a gasket that locks onto the base allowing pressure buildup.
A gauge that regulates the pressure inside the canner. There are 2 types of gauges, dial or weighted.
The dial gauge gives a visual display of the pressure. They must be checked for accuracy often and are prone to leak. I much prefer the weighted gauge. This is a device which can easily be set for 5, 10 or 15 pounds of pressure. It “jiggles” during processing releasing small amounts of steam in order to maintain the proper pressure.
Pressure canners need to be checked on a regular basis. If you use a dial gauge it needs to be calibrated every year. Many county extension offices do this. Check the gasket for stretching, nicks or tears. They are easy to replace and are readily available at hardware stores or by mail order.
Many folks are afraid to use pressure canners. They are entirely safe if you follow the manufacturer's instructions and do not try to take any shortcuts.
The Canning or "Mason"Jar
The container of choice for home canning today is known as the Mason jar with a two piece lid.
Invented in 1858 by John Landis Mason, the jar has evolved to what we use today. Early Mason jars were sealed with a zinc screw cap. The jar had a threaded neck onto which the lid screwed onto. The seal was accomplished by a “jar rubber” which fit between the lid and the neck.
Today’s modern canning jars with self sealing lids have been in use for over 50 years. They come in regular and wide mouth; and in sizes ranging from a ½ pint up to a ½ gallon.
The closure consists of a lid or disc which is heated in boiling water for a minute or two and placed onto the neck of the jar. The screw band is applied and tightened over the lid. The jars are then processed, as the jar cools the lids is pulled down onto the neck thus creating a seal.
The jars and screw bans are reusable; the lids are only used once.
Use only Mason jars when canning, they are designed to hold up to the pressure and heat incurred during processing. Do not use mayonnaise or any other jars not designed for canning.
Mason jar with 2 piece lid
Other Helpful Tools for Canning
There are a few more pieces of equipment that I want to touch on that are very helpful.
- A canning funnel is helpful when filling jars. It makes it very easy to measure the suggested head space.
- A Jar lifter, designed for placing and removing canning jars from water bath or pressure canners.
- A magnetic lid lifter. The lids need to be placed into hot water to ensure a proper seal. This lid lifter makes it easy to remove the lids form the hot water.
Top left, canning funnel, top right, Jar lifter
bottom, magnetic lid lifter
Here's a link to the next installment of Preserving the Bounty, where I’ll discuss freezing fruits and vegetables and also dehydration.
Paul’s Garden Tip
If you’re like me every spring I would buy several balls of garden twine to tie up plants in the garden. Usually a week or two into the season the twine was a tangled mess. I have solved that problem by using assorted containers to hold my twine. From left a detergent container, center a 3 gallon pail from Dunkin Doughnuts and right, a container with a screw lid. Drill a hole in the lid a bit larger than the twine. Place the twin e into the container and feed it through the hole. Be sure to feed the twine form the center of the spool or ball of twine. It will never tangle on you.
If you wish a piece of hacksaw blade can be hot glued to the container to cut your twine.