Preserving Food Safely: Canning Basics

By Terrie James/Hempstead Cooperative Extension Service, 08/15/22 8:25 PM
Preserving Food Safely: Canning Basics
Does the idea of having jars of delicious “fresh from the garden” home canned food in your
pantry for those cold, dreary winter months ahead seem appealing? Does the idea of using a
pressure canner or water bath canner to preserve that summer bounty seem scary and hard to do?
You are not alone, many people particularly home gardeners find the idea of preserving their
garden bounty appealing, but some are nervous about using canning equipment especially
presser canners safely to prevent food borne illness.
The good news is canning both pressure and water bath are not that difficult if you are willing to
follow the latest research guidelines to ensure food is prepared, processed, and stored safely to
prevent the growth of toxins that cause food borne illness. Family and Consumer Sciences
Extension Agents who work for Land Grant Universities in the United States in partnerships with
state and local governments are resources for the latest research in preserving food safely.
True home canning is when the food is heated enough to destroy pathogens or sufficiently acid
enough to prevent growth of all spores of Clostridium botulinum (that causes botulism) and other
pathogens during room temperature storage on the shelf.
When canning fruits or vegetables, begin with fresh foods picked at their peak of quality. Can
within 6 to 12 hours after harvest for most vegetables. Wash everything: equipment, jars, lids,
rings, utensils, countertops, your hands, and the produce thoroughly. Washing produce means
rinsing thoroughly without soap in cool water and scrubbing the outside especially if it has
places that can hold dirt or contaminants.
Follow the recipe exactly. Do not use recipes older than 1996. You should prepare food as
directed in recipe. This means if a recipe says peel and chop then peel and chop. Don’t improvise
with the amount of ingredients. If a recipe calls for 7 cups of sugar, don’t use 6 because you want
reduced sugar or 8 because it’s not sweet enough, use 7 cups as stated. Extra sugar or fat,
oversize food pieces, and added thickeners slow down heat penetration which is key in killing off
pathogens.
Follow process times exactly – carefully read the recipes because the processing time is different
for different size jars. The bottom line is the size of jar, size of food, consistency of liquid all
have an effect on heat penetration. All factors are considered when determining the “heat up” and
“cool down” times in canning. The times are included in the sterilizing value of the process. The
recipes have been tested to determine the length of time it takes to adequately heat the coldest
spot in the jar.
The recipe also includes what type of canning method to use: water bath or pressure. The water
bath canner is used for high acid foods only. The acid kills Clostridium botulinum spores which
are highly toxic and account for 25% of foodborne illness primarily caused from improperly
home canned food. Fruits, pickles, jams, jellies, and sweet preserves have a pH of 4.6 or less
indicating high acidity. Yeast, mold, and most bacteria are destroyed at boiling temperatures
(212ºF) reached in the water bath canning process.
Pressure canning is necessary for vegetables, meat, and seafood. While primarily used for low
acid foods, some high acid foods and mixed recipes of both low and high acid foods require
pressure canning. Pressure canners heat products to at least 240ºF to destroy pathogens and
prevent spoilage and it is required for low acid foods to be able to kill C. botulinum spores.
Other factors to consider in canning are using jars recommended by manufacturers for home
canning, along with corresponding lids and rings. Lids may not be reused, but rings and jars can
be reused if free of dents and nicks and properly cleaned and sanitized according to manufacturer
and recipe guidelines.
Recipe resources include the USDA Guide to Complete Home Canning (free download)
available at https://nchfp.uga.edu/publications/publications_usda.html#gsc.tab=0 or you can
order a printed copy at that site. The National Center for Home Food Preservation website is a
wealth of information with free downloads at the site:
https://nchfp.uga.edu/publications/publications_usda.html#gsc.tab=0. Their publication, So Easy
Extension websites are good resources including the University of Arkansas Division of
Agriculture Cooperative Extension Service: https://www.uaex.uada.edu/.
Educational institutions and government websites are considered credible and end in .edu and
.gov. Also, manufacturers of food preservation equipment and supplies will have recipes and
other food preservation information.
For more information on food preservation, food safety, and related topics contact Terrie James
at tjames@uada.edu or call 870-777-5771