|
Canned foods should be
stored under proper conditions in order that they shall keep to the best
advantage.
A knowledge of the causes
and results of the spoiling of canned goods is of great importance.
24. Storage of Canned
Foods. If intended for market, canned fruits, vegetables, and meats
should be stored a month or more to be certain that all goods marketed
are in sound condition. A cool dark storage room is best for permanent
storage, while a warm room is best if it is desired to ascertain whether
the material will keep. Warm temperatures cause rapid growth of the
microorganisms causing spoiling.
Fruits in jars will
retain their color better if the jars are wrapped in paper to exclude
the light.
The storeroom must be dry
to prevent molding of jars and rusting of cans. Freezing and thawing
injures the flavor and texture of canned goods; therefore, the storage
room should be kept above the freezing point.
25. Spoiling of Canned
Foods—Botulinus Poisoning. As stated in previous chapters, spoiling
is due to the growth of microorganisms.
Fruits, because of their
composition, are spoiled by molds or yeast. The spoiling of jars or cans
of fruits usually means imperfect sealing and leaky containers, into
which yeasts or molds gain access after sterilization. As the cans or
jars cool after sterilization the contents contract, forming a vacuum,
through which air with mold and yeast cells is drawn if the container
has a small leak.
The products formed in a
spoijed can or jar of fruit are alcohol and carbon dioxide from
fermentation of the sugar. No poisonous compounds are formed. The carbon
dioxide gas will cause the jar or can to burst if there is no other way
for it to escape.
Vegetables are spoiled
most commonly after sterilization by spore-bearing bacteria not killed
during sterilization. Corn, peas, and asparagus are difficult to
sterilize and often develop growths of various resistant bacteria.
Vegetables are also spoiled by bacteria gaining entrance through leaks
after sterilization. In these cases, the bacteria are usually of the
lactic acid non-spore bearing type, in contrast to the non-acid forming
spore bearers met with in imperfectly sterilized cans of vegetables.
Usually the products of
decomposition in vegetables are harmless, although often vile in taste
and odor. Occasionally, however, botulinus bacilli spores. will be
present and survive the heating process. These develop and produce a
very violent poison. Many fatal cases have come to the notice of state
boards of health, where death was caused by the use of imperfectly
sterilized corn, peas, or string beans. The poison is so powerful that a
single grain of corn from a can heavily infected with botulinus will
cause death.
The presence of botulinus
is hard to detect. Usually a rancid odor will be noticed and gas
pressure normally develops, but the flavor may not be objectionable.
The poison is destroyed
by heating the vegetables to boiling for half an hour after taking from
the can. Most fatal cases have resulted where the vegetables have been
used from the can or jar for salads, etc., without cooking thoroughly
before serving.
Suspected vegetables
should not be fed to chickens or animals without thorough boiling
because the poison is fatal to animals as well as to human beings.
The cases of poisoning
have occurred where vegetables have been canned by the hot-pack method
without sterilization in the can. Where thorough sterilization by any
one of the methods given in paragraph 21 is employed there is no danger
from botulinus. Tomatoes do not develop botulinus. Other vegetables do.
Meats spoil in ways
similar to those noted for vegetables and there is danger from botulinus
poisoning unless the meats are thoroughly sterilized. Fish and other
marine products are especially difficult to sterilize and therefore must
be canned with great care. Dr. Dickson of Stanford has done a great deal
of work on the occurrence of botulinus in food products, especially in
canned vegetables. |
