One of the many problems that confront the American housewife is the
supply of vegetables for her table during the winter months. "What
can I have for dinner today?" is a question often heard. Since the
advent of the modern greenhouse and the forcing of vegetables under
glass, fresh vegetables can usually be found at any time in the
markets of the large cities. But the cost of forcing vegetables or
growing them out of season is and will continue to be very great. This
makes the price so high as almost to prohibit their use by people of
moderate means, except as a luxury. A healthful diet, however, must
include vegetables, and therefore the housewife turns to canned goods
as the only alternative. These are sometimes poor substitutes for
the fresh article, especially the cheaper commercial grades, which
necessarily lack the delicate flavor of the fresh vegetable. There
is practically no danger, however, from contamination with tin or
other metals providing the containers are made of proper materials
and handled carefully. In some cases the proper care is not taken in
packing vegetables for market. The decayed and refuse portions are not
so carefully removed as they should be and the requisite degree of
cleanliness is not observed in their packing. Happily, however, such
carelessness is not general.
Every housewife may run a miniature canning factory in her own kitchen,
and on the farm this is especially economical and desirable, the
economy being less pronounced in the case of city dwellers, who must
buy their fruits and vegetables. Enough vegetables annually go to waste
from the average farm garden to supply the table during the entire
winter. But usually the farmer's wife cans her tomatoes, preserves
her fruits, and leaves her most wholesome and nutritious vegetables
to decay in the field, under the impression that it is impossible to
keep them. This is a great mistake. It is just as easy to keep corn or
string beans as it is to keep tomatoes, if you know how.
_Sterilization._--The great secret of canning or preserving lies in
complete sterilization. The air we breathe, the water we drink, all
fruits and vegetables, are teeming with minute forms of life which we
call bacteria, or molds, or germs. These germs are practically the
sole cause of decomposition or rotting. The exclusion of air from
canned articles, which was formerly supposed to be so important,
is unnecessary provided the air is sterile or free from germs. The
exclusion of air is necessary only because in excluding it we exclude
the germ. In other words, air which has been sterilized or freed from
germs by heat or mechanical means can be passed continuously over
canned articles without affecting them in the least. If a glass bottle
is filled with some vegetable which ordinarily spoils very rapidly--for
instance, string beans--and, instead of a cork, it is stoppered with a
thick plug of raw cotton and heated until all germ life is destroyed,
the beans will keep indefinitely. The air can readily pass in and out
of the bottle through the plug of cotton, while the germs from the
outside air cannot pass through, but are caught and held in its meshes.
This shows that the germs and their spores or seeds are the only causes
of spoilage that we have to deal with in canning.
Germs which cause decay may be divided into three classes--yeasts,
molds and bacteria. All three of these are themselves plants of a very
low order, and all attack other plants of a higher order in somewhat
the same way. Every housewife is familiar with the yeast plant and its
habits. It thrives in substances containing sugar, which it decomposes
or breaks up into carbonic acid and alcohol. This fact is made use of
in bread making, as well as in the manufacture of distilled spirits.
Yeasts are easily killed, so they can be left out of consideration in
canning vegetables. Molds, like yeasts, thrive in mixtures containing
sugar, as well as in acid vegetables, such as the tomato, where neither
yeasts nor bacteria readily grow. Although more resistant to heat than
yeasts, they are usually killed at the temperature of boiling water. As
a general rule, molds are likely to attack jellies and preserves and
are not concerned with the spoiling of canned vegetables. The spoiling
of vegetables is due primarily to bacteria.
The reproduction of bacteria is brought about by one of two processes.
The germ either divides itself into two parts, making two bacteria
where one existed before, or else reproduces itself by means of spores.
These spores may be compared with seeds of an ordinary plant, and they
present the chief difficulty in canning vegetables. While the parent
bacteria may be readily killed at the temperature of boiling water, the
seeds retain their vitality for a long time even at that temperature,
and upon cooling will germinate, and the newly formed bacteria will
begin their destructive work. Therefore it is necessary, in order to
completely sterilize a vegetable, to heat it to the boiling point of
water and keep it at that temperature for about one hour, upon two or
three successive days, or else keep it at the temperature of boiling
water for a long period of time--about five hours. The process of
boiling upon successive days is the one that is always employed in
scientific work and is much to be preferred. The boiling on the first
day kills all the molds and practically all of the bacteria, but does
not kill the spores or seeds.
As soon as the jar cools these seeds germinate and a fresh crop of
bacteria begin work upon the vegetables. The boiling upon the second
day kills this crop of bacteria before they have had time to develop
spores. The boiling upon the third day is not always necessary, but is
advisable in order to be sure that the sterilization is complete. Among
scientists this is called fractional sterilization, and this principle
constitutes the whole secret of canning. If the housewife will only
bear this in mind she will be able with a little ingenuity to can any
meat, fruit, or vegetable.
_Exclusion of the Air._--Even after sterilization is complete the work
is not yet done. The spores of bacteria are so light that they float
about in the air and settle upon almost everything. The air is alive
with them. A bubble of air no larger than a pea may contain hundreds of
them. Therefore it is necessary after sterilizing a jar of vegetables
to exclude carefully all outside air. If one bacterium or one of its
spores should get in and find a resting place, in the course of a few
days the contents of the jar would spoil. This is why the exclusion of
air is an important factor, not because the air itself does any damage
but because of the ever-present bacteria.
All of this may seem new fashioned and unnecessary to some
housekeepers. Persons have quite often heard it said: "My grandmother
never did this, and she was the most successful woman at canning that
I ever knew." Possibly so, but it must be remembered that grandmother
made her preserves--delicious they were, too--and canned her tomatoes,
but did not attempt to keep the most nutritious and most delicately
flavored vegetables, such as lima beans, string beans, okra, asparagus,
or even corn.
_So-Called "Preserving Powders."_--There are a great many brands of
so-called "preserving powders" on the market. These are sold not only
under advertised trade names but by druggists and peddlers everywhere.
In the directions for use the housewife is told to fill the jar with
the fruit or vegetable to be canned, to cover with water, and to
add a teaspoonful of the powder. It is true that these powders may
prevent the decay of the fruit or vegetable, but they also encourage
uncleanly, careless work, and in the hands of inexperienced persons may
be dangerous. While with small doses the influence may not be apparent
in an adult in normal health, with a child or an invalid the effect
may be of a serious nature. The proper way to sterilize is by means
of heat, and as this can be done very easily and cheaply the use of
chemical preservatives in canning is not to be recommended.
_Kinds of Jars._--The first requisite for successful canning is a good
jar. Glass is the most satisfactory. Tin is more or less soluble in
the juices of fruits and vegetables. Even the most improved styles of
tin cans which are lacquered on the inside to prevent the juice from
coming in contact with the tin are open to this objection. While the
amount of tin dissolved under these conditions is very small, enough
does come through the lacquer and into the contents of the can to be
detected in an ordinary analysis. While the small amount of tin may not
be injurious, it gives an undesirable color to many canned articles.
Tin cans can not readily be used a second time, while glass with proper
care will last indefinitely.
There are a great many kinds of glass jars on the market, many of them
possessing certain distinct points of advantage. The ordinary screw-top
jar is the one in most common use. Although cheap in price, these jars
are the most expensive in the long run. The tops last only a few years
and, being cheaply made, the breakage is usually greater than that of
a better grade of jar. The tops also furnish an excellent hiding place
for germs, which makes sterilization very difficult.
The most satisfactory jar is the one which has a rubber ring and glass
top, held in place by a simple wire spring. There are several brands
of these jars on the market, so no difficulty should be experienced in
obtaining them. Vegetables often spoil after being sterilized because
of defective rubbers. It is poor economy to buy cheap rubbers or to use
them a second time. As a general rule black rubbers are more durable
than white ones.
Buy a good grade of jar. The best quality usually retails at from a
dollar to a dollar and twenty-five cents a dozen. The initial expense
may be, therefore, somewhat high, but with proper care they should last
many years. The annual breakage should be less than 3 per cent on the
average. In selecting a jar always give preference to those having wide
mouths. In canning whole fruit or vegetables and in cleaning the jars
the wide mouth will be found to be decidedly preferable.
_Containers for Sterilizing._--A tin clothes boiler with a false
bottom made of wire netting cut to fit may be used as a container for
sterilizing. The netting is made of medium-sized galvanized wire (No.
16) with one-half inch mesh. A false bottom is absolutely necessary, as
the jars will break if set flat upon the bottom of the boiler. Narrow
strips of wood, straw, or almost anything of this nature may be used
for the purpose, but the wire gauze is clean and convenient.
There are several varieties of patent steamers or steam cookers in
common use. These have either one or two doors and hold a dozen or more
quart jars. They are ideal for canning, but they are somewhat expensive
and can be easily dispensed with. A common ham boiler or clothes boiler
with a tight-fitting cover will answer every purpose.--(F. B. 359.)
_Selection and Preparation of Vegetables._--The first step in
successful canning is the selection and preparation of the vegetables.
Never attempt to can any vegetable that has matured and commenced
to harden or one that has begun to decay. As a general rule, young
vegetables are superior in flavor and texture to the more mature
ones. This is especially true of string beans, okra, and asparagus.
Vegetables are better if gathered in the early morning while the dew
is still on them. If it is impossible to can them immediately, do not
allow them to wither, but put them in cold water, or in a cold, damp
place and keep them crisp until you are ready for them. Do your canning
in a well-swept and well-dusted room. This will tend to reduce the
number of spores floating about and lessen the chances of inoculation.