Michigan State University Extension
Preserving Food Safely - 01600948
10/13/97
Equipment for heat-processing home-canned food is of
two main types--boiling-water canners and pressure canners.
Most are designed to hold seven quart jars or eight to nine
pints. Small pressure canners hold four quart jars; some
large pressure canners hold 18 pint jars in two layers, but
hold only seven quarts jars. Pressure saucepans with
smaller volume capacities are not recommended for use in
canning. Small capacity pressure canners are treated in a
similar manner as standard larger canners, and should be
vented using the typical venting procedures.
Low-acid foods must be processed in a pressure canner
to be free of botulism risks. Although pressure canners may
also be used for processing acid foods, boiling-water
canners are recommended for this purpose, because they are
faster. A pressure canner would require from 70 to 115
total minutes to can a load of jars; the total time for
canning most acid foods in boiling water varies from 25
to 60 minutes. A boiling-water canner loaded with filled
jars requires about 20 to 30 minutes of heating before its
water begins to boil. A loaded pressure canner requires
about 12 to 15 minutes of heating before it begins to vent;
another l0 minutes to vent the canner; another 5 minutes
to pressurize the canner; another 8 to 10 minutes to process
the acid food; and, finally, another 20 to 60 minutes to
cool the canner before removing jars.