General:
Can food be re-canned if the lid does not seal?Canned food can safely be re-canned if
the unsealed jar is discovered within 24 hours. To re-can, remove
the lid and check the jar sealing surface for tiny nicks. Change
the jar. If necessary, add a new treated lid and reprocess using
the same processing time.
If my recipe doesn't call for processing, do I need to do so?
Many recipes passed down through the years or
found in older cookbooks do not include instructions for processing.
The foods are usually canned by the open kettle method, sealed and
stored. Foods prepared in this manner present a serious health
risk - particularly low acid foods. To minimize the risk of food
spoilage, all high acid foods should be processed in a water bath canner
or pressure canner and all low acid foods in a pressure canner.
Do I really need to leave a certain amount of headspace in the jar?
Yes, leaving the specified amount of headspace
in a jar is important to assure a vacuum seal. If too little headspace
is allowed the food may expand and bubble out when air is being forced
out from under the lid during processing. The bubbling food may
leave a deposit on the rim of the jar or the seal of the lid and prevent
the jar from sealing properly. If too much headspace is allowed,
the food at the top is likely to discolor. Also, the jar may not
seal properly because there will not be enough processing time to drive
all the air out of the jar.
How long will canned food keep?
Properly canned food stored in a cool, dry
place will retain optimum eating quality for a least 1 year.
Canned food stored in a warm place near hot pipes, a range, a furnace,
or in indirect sunlight may lose some of its eating quality in a few
weeks or months, depending on the temperature. Dampness may
corrode cans or metal lids and cause leakage so the food will spoil.
Is it necessary to sterilize jars before canning?
Jars do not need to be sterilized before
canning if they will be filled with food and processed in a boiling
water bath canner for 10 minutes or more or if they will be processed in
a pressure canner. Jars that will be processed in a boiling water
bath canner for less than 10 minutes, once filled, need to be sterilized
first by boiling them in hot water for 10 minutes before they're filled.
Is it safe to process food in the oven?
No. This can be dangerous because the temperature will vary
according to the accuracy of oven regulators and circulation of heat.
Dry heat is very slow in penetrating into jars of food. Also, jars
explode easily in the oven.
Can two layers of jars be processed in a canner at one time?
Yes. Two layers can be processed at one
time, in either the boiling water bath or pressure canner. Place a
small wire rack between the layers so water or steam will circulate
around each jar. Make certain that the water covers the tops of
all jars by 1 inch in a boiling water bath canner. The pressure
canner should have 2 to 3 inches of water in the bottom.
Is it necessary to exhaust a pressure canner?
Yes, it is very important to allow steam to
escape for 10 minutes before closing the valve, or placing the weight on
the vent. If the canner is not exhausted, the inside temperature
may not correspond to the pressure on the gauge.
Should liquid lost during processing be replaced?
No. Loss of liquid does not cause food to
spoil, though the food above the liquid may darken. If, however,
the loss is excessive (for example, if at least half of the liquid is
lost), refrigerate the jar(s) and use within 2 to 3 days.
Is it all right to reuse jar fittings (lids and bands)?
Lids should not be used a second time since the
sealing compound becomes indented by the first use, preventing another
airtight seal. Screw band may be reused unless they are badly
rusted or the top edge is pried up which would prevent a proper seal.
Why is open kettle canning not recommended?
In open kettle canning, food is cooked in an
ordinary kettle, then packed into hot jars and sealed without
processing. The temperatures obtained in open kettle canning are
not high enough to destroy all spoilage and food poisoning organisms
that may be in the food. Also, microorganisms can enter the food
when it is transferred from the kettle to jar and cause spoilage.
Why do the undersides of metal lids sometimes discolor?
Natural compounds in some foods, particularly acids, corrode metal
and make a dark deposit on the underside of jar lids. This deposit
on lids of sealed, properly processed canned foods is harmless.
What causes jars to break in a canner?
Breakage can occur for several reasons:
1. Using commercial food jars rather than jars manufactured for
home canning. 2. Using jars that have hairline cracks.
3. Putting jars directly on bottom of canner instead of on a rack.
4. Putting hot food in cold jars. 5. Putting jars of
raw or unheated food directly into boiling water in a the canner, rather
than into hot water (sudden change in temperature-too wide a margin
between temperature of filled jars and water in canner before
processing).
If I find mold growing inside a jar of canned food, can I just scrape
it off and eat the food?
Mold growth in foods can raise the pH of the
food. In home canned products, this could mean that the high acid
products could become low acid and therefore run the risk of botulism or
other bacterial spoilage. Thus, any home canned product that shows
signs of mold growth should be discarded. The exception to this is
jellied products. In these the high sugar content would prevent
the growth of Clostridium botulinum. In jellied products, remove
any surface mold plus 1/2 inch of the good product underneath and then
use the rest immediately. Jellied products with extensive mold
should be discarded.
How can I remove scale or hard-water film from canning jars?
Soak jars for several hours in a
solution containing 1 cup of vinegar and 1 gallon of water.
 
Vegetables and Fruits
Is it safe to can food without salt?
Yes. Salt is used for flavor only and is
not necessary to prevent spoilage.
Is it safe to can fruits without sugar?
Yes. Sugar is added to improve flavor,
help stabilize color, and retain the shape of the fruit. It is not
added as a preservative.
Can fruits and vegetables be canned without heating if aspirin is used?
No. Aspirin should not be used in
canning. It cannot be relied on to prevent spoilage or to give
satisfactory products. Adequate heat treatment is the only safe
procedure.
Is it safe to can green beans in a boiling water bath if vinegar is used?
No. Recommended processing methods must
be used to assure safety. Recommended processing times cannot be
shortened if vinegar is used in canning fresh vegetables (this does not
refer to pickled vegetables).
Should all vegetables be precooked before canning?
For best quality, yes. However, some
vegetables can be packed raw or cold into jars before being processed in
the pressure canner.
What vegetables expand instead of shrink during
processing?
Corn, peas, and lima beans are starchy and
expand during processing. They should be packed loosely.
What causes corn to turn brown during processing?
This occurs most often when too high a
temperature is used causing caramelization of the sugar in the corn.
It may also be caused by some minerals in the water used in canning.
Why is canning summer squash or zucchini not recommended?
Recommendations for canning summer squashes,
including zucchini, that appeared in former editions of "So Easy to
Preserve" have been withdrawn due to uncertainty about the determination
of processing times. Squashes are low-acid vegetables and require
pressure canning for a known period of time that will destroy the
bacteria that cause botulism. Documentation for the previous
processing times cannot be found, and reports that are available do not
support the old process. Slices or cubes of cooked summer squash
will get quite soft and pack tightly into the jars. The amount of
squash filled into a jar will affect the heating pattern in that jar.
It is best to freeze or pickle summer squashes, but they may also be
dried.
Can I can my own salsa recipe?
Salsas are usually mixtures of acid and low-acid ingredients; they are an example of an acidified food.
The specific recipe, and sometimes preparation method, will determine if
a salsa can be processed ina boiling water canner or a pressure canner.
A process must be scientifically determined for each recipe. To
can salsa at home, use tested recipes for salsa.
Can I can bread or cake in a jar?
These products are not recommended for canning;
choose recipes that you can freeze. In fact, most of these
products are not really "canned". The directions call for baking
in the jar and then closing with a canning lid. Many recipes for
quick breads and cakes are low-acid and have the potential for
supporting the growth of a bacteria like Clostridium botulinum if it is
present inside the closed jar. One university's research showed a
high potential for problems. You will see these products made
commercially; however, additives, preservatives, and processing
controls not available for home recipes are used. Canning jar
manufacturers also don't endorse baking in their canning jars.
How do I can oil with herbs? Can I can pesto?
Herbs and oils are both low-acid and together
could support the growth of the disease-causing Clostridium botulinum
bacteria. Oils may be flavored with herbs if they are made up for
fresh use, stored in the refrigerator, and used within 2 to 3 days.
There are no canning recommendations. Fresh herbs must be washed
well and dried completely before storing in the oil. The very best
sanitation and personal hygiene practices must be used. Pesto is
an uncooked seasoning mixture of herbs, usually including fresh basil,
and some oil. It may be frozen for long term storage; there are no
home caning recommendations.
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