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Q. W
hy is the cooking liquid used for packing
some vegetables and boiling water for others?
A. Cooking liquid is recommended for packing most
vegetables because it may contain minerals and
vitamins dissolved out of the food. Boiling water is
recommended when cooking liquid is dark, gritty, or
strong-flavored, and it may be used if there isn’t
enough cooking liquid.
Processing time is the same whether hot cooking
liquid or boiling water is used for packing.
Q. Why is liquid sometimes lost from glass jars
during processing?
A. Loss of liquid may be due to a number of things:
1) Cooking food too short a time to drive out the air
that is in it before packing it in the jars.
2) Packing jars too full.
3) Leaving air bubbles in the jars.
4) Not keeping pressure steady in a pressure canner.
5) Lowering pressure too suddenly at the end of the
processing period.
6) Food is packed to tightly.
7) Food is processed at too high a temperature.
8) Leakage of steam between lid and bottom of
pressure cooker.
Q. Should liquid lost during processing be replaced?
A. No, never open a jar and refill with liquid – this
would let in bacteria, and you’d need to process
again. Loss of liquid does not cause food to spoil,
although the food above the liquid may darken.
Q. What causes cloudy liquid in canned fruits and
vegetables?
A. Cloudy liquid may be a sign of spoilage. It may
also be caused by the minerals in hard water or by
starch from overripe vegetables.
Q. How can you tell whether food with cloudy
liquid is spoiled?
A. Boil the food and note the odor. Do not taste or
use any food having an off odor.
Q. W
hy does canned fruit sometimes float in jars?
A. Fruit may float because the pack is too loose or
the syrup too heavy. It’s also possible that air in the
tissues of the fruit has not all been forced out during
heating and processing.
Q. Why does my food turn moldy after processing?
A. Mold can only form in the presence of air.
Therefore, jars are not sealed if mold is present.
Q. What makes canned foods change color?
A. Darkening of foods at the tops of jars may be
caused by oxidation due to air in the jars or by too
little heating or processing to destroy enzymes.
Over-processing may cause discoloration of foods
throughout the containers.
Pink and blue colors sometimes seen in canned
pears, apples and peaches are caused by chemical
changes in the coloring matter of the fruit.
Iron and copper from utensils used in preparing
foods, or from the water in some localities, may
cause brown, black and gray colors in some foods.
Corn turns brown during processing when too high
a temperature is used. The high temperature causes
a caramelization of the sugar in corn. It may also be
caused by some chemical, such as iron, in the water
used in canning.
When canned corn turns brown, the discoloring
may be due to the variety of corn, the state of
ripeness, or over-processing. A common cause of
highly colored foods fading is the dissolving of
coloring materials by the packing liquid. The use of
plain tin cans will cause some foods to lose color.
Q. Is it safe to eat discolored canned foods??
A. The color changes noted above do not mean the
food is unsafe to eat. However, spoilage may also
cause color changes. Any canned food that has an
unusual color should be examined carefully before
use.
Q. Why does the underside of metal lids sometimes
discolor?
A. Natural compounds in some foods corrode the
metal and make a brown or black deposit on the
underside of the lid. This deposit is harmless and
doesn’t mean that the food in the jar is unsafe to eat.
QUESTIONS AND ANSWERS ON HOME CANNING
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