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Using the process time for canning food at
sea level may result in spoilage if you live
at altitudes of 1,000 feet or more. Water
boils at lower temperatures as altitude
increases. Lower boiling temperatures are
less effective for killing bacteria.
Increasing the process time or canner
pressure compensates for lower boiling
temperatures.
Therefore, when following canning
directions in this series, select the proper
processing time or canner pressure for the
altitude where you live. If you do not
know the altitude, contact your local
county Extension agent. An alternative
source of information would be the local
district conservationist with the Soil
Conservation Service.
Equipment and
Methods Not Recommended
Open-kettle canning and the processing of
freshly filled jars in conventional ovens,
microwave ovens, and dishwashers are not
recommended, because these practices do
not prevent all risks of spoilage. Steam
canners are not recommended because
processing times for use with current
models have not been adequately
researched.
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Because steam canners do not heat foods
in the same manner as boiling-water canners, their
use with boiling-water process times may result in
spoilage. It is not recommended that pressure
processes in excess of 15 PSI be applied when using
new pressure canning equipment. So-called canning
powders are useless as preservatives and do not
replace the need for proper heat processing. Jars
with wire bails and glass caps make attractive
antiques or storage containers for dry food
ingredients but are not recommended for use in
canning. One-piece zinc porcelain-lined caps are
also no longer recommended. Both glass and zinc
caps use flat rubber rings for sealing jars, but too
often fail to seal properly.
Ensuring High Quality Canned Foods
Begin with good-quality fresh foods suitable for
canning. Quality varies among varieties of fruits and
vegetables. Many County Extension offices can
recommend varieties best suited for canning.
Examine food carefully for freshness and
wholesomeness. Discard diseased and moldy food.
Trim small diseased lesions or spots from food.
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Can fruits and vegetables picked from your garden
or purchased from nearby producers when the
products are at their peak of quality-within 6 to 12
hours after harvest for most vegetables. For best
quality, apricots, nectarines, peaches, pears, and
plums should be ripened 1 or more days between
harvest and canning. If you must delay the canning
of other fresh produce, keep it in a shady, cool place.
Fresh home-slaughtered red meats and poultry
should be chilled and canned without delay. Do
not can meat from sickly or diseased animals.
Ice fish and seafoods after harvest, eviscerate
immediately. You must can them within 2 days.
Maintaining Color
and Flavor in Canned Food
To maintain good natural color and flavor in
stored canned food you must: remove oxygen
from food tissues and jars; quickly destroy the
food enzymes; obtain high jar vacuums and
airtight jar seals.
Follow these guidelines to ensure that your
canned foods retain optimum colors and flavors
during processing and storage: use only
high quality foods which are at the proper
maturity and are free of diseases and bruises.
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