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Home Canning - A Brief Overview


Growing up in the South, the end of summer and into fall brought neighbors to our front door, arms loaded down with colorful, packed Mason jars.  Mom gratefully (and gracefully) invited them in, put the jars away in the mysterious pit of the upper cabinets, and sat to drink coffee or tea with whichever neighbor was there at the moment. 

Home canning is a method of preserving fruit, vegetables and meat.  Foods are packed into Mason jars and put in a water bath or pressure canner where the food is essentially cooked in the jar and the air is pushed out of the jar, preserving the food for use months down the road.  Canning must be done correctly to insure that bacteria does not grow in the jar and produce dangerous toxins that can make the people eating the preserved food sick.

Types of Canning

There are two ways to can – water bath and pressure canning.  In both methods, the jars are heated for a specific amount of time and at a specific temperature.  Foods should never be processed in a microwave, conventional oven, or dishwasher.

In the water bath method, the jars are immersed in boiling water in a deep kettle or pot.  Water bath canning can be used when processing high-acid foods such fruit (except figs) and tomatoes.  It is not suitable for other kinds of vegetables, however.  The microorganisms found in high-acid foods are easily killed by a water bath method so this is safe to use with these foods.  Other bacteria, like the one that produces botulism toxin, cannot grow in high-acid foods.

In pressure canning, a specially made kettle is used which has a lid and pressure gauge.  A pressure canner can reach temperatures over 250 degrees.  Pressure canning must be used for low-acid foods such as figs, meats and all vegetables except tomatoes.  Harmful bacteria that can grow in low-acid foods can survive in boiling water for several hours making a water bath an unsuitable preserving method.  The high temperature in a pressure canner, however, will kill this harmful bacteria.

Mason jars.  Photo courtesy of Patrick Q (flickr).

Mason jars. Photo courtesy of Patrick Q (flickr).

Canning Equipment

Both methods of canning use essentially the same equipment, except for the canner itself.  When using a water bath, use a special canner which is a deep kettle with a rack for holding the jars, or use a pot that is deep enough for boiling water to cover the jars by at least one inch.  A pressure canner is a special kettle made specifically for pressure canning.  It has a rack inside to hold the jars, a tight-fitting lid with a gasket, and a pressure gauge.  The gasket on the lid prevents steam from escaping the kettle.  There are two types of gauges – dial gauge and weighted gauge.  A dial gauge has a needle that moves on a scale to show the pressure inside the kettle.  A dial gauge must be tested annually to insure its accuracy.  A weighted gauge allows the pressure in the canner to reach the desired point and then releases the excess steam to keep the pressure from rising too high.

Other necessary equipment includes canning jars (usually Mason jars), 2-part canning lids, jar lifter, timer and metal tongs.  Some equipment is not necessary but makes preparing the food and jars easier.  These convenience items include funnels, apple corers and cherry pitters.

A water bath canner.  Photo courtesy Chiot Run (flickr).

A water bath canner. Photo courtesy Chiot Run (flickr).

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Safety and Spoilage

Canned foods can be stored safely for at least a year.  Jars should be labeled with the processing date and stored in a cool, dry, dark place.  They should not be kept near hot pipes, a furnace, stove or in sunlight.

Before using, check the canned food for spoilage.  The most obvious signs are leakage, bulging lids or loss of seal.  Bulging lids and loss of seal indicate that gas has formed in the jar.  After opening, look for cloudy liquid, spurting liquid, odor and mold.  Never taste the food to check for spoil.  Even very small amounts of botulism toxin can be fatal to humans.  Spoiled food shoul not be fed to animals either. 

Low-acid food should always be boiled for ten minutes before tasting.  However if the food shows signs of spoilage, boiling will not necessarily kill the toxins.  Cloudy liquid, without other signs of spoilage, could simply be from minerals in hard water or starch from vegetables.  Canned foods with cloudy liquid should be boiled to check for other signs.  If the food foams or has a bad odor, throw it out.

Home canning has again become popular, especially as more families try to find greener ways of living.  Households that grow their own vegetables and fruit can preserve their excess crops and have home grown food for the rest of the year.  Many other families find that home canning well worth the time and energy required when the end result is nutritious, healthy, additive-controlled food.

Home Canning Basics Part 1

Home Canning Basics Part 2 - Two Types of Canners

Home Canning Basics Part 3 -

Home Canning Basics Part 4 - Water Bath Canning

Home Canning Basics Part 5 - Pressure Canning

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daisyjae from Canada on July 27, 2010:

Your canning hubs are great! Lots of info and you have answered some of my questions. And thanks for the link. Rated up and stumbled.

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