TESTS FOR JARS cont'd
2. Screw-top Jars.––Use only enameled, lacquered or
vulcanized tops. Screw the top on tightly without the rubber. If the tip of
a knife or finer-nail can be inserted under the rim, the tops should not be
used for cold-pack canning. If the defect is very slight, however, it may be
remedied by pressing a knife handle on the lower edge against a hard
surface, thus straightening the offending bulge. Another test is made by
putting on the rubber, screwing the top on tightly and then pulling the
rubber out. If the rubber returns to place, the top does not fit and should
not be used on that jar.
Fig. 9. Wire rack for jars.
3. Vacuum seal jars may be tested in the same way as the
glass-top jars. See if the tops rock if tapped, when placed on the jar
STANDARDS AND TESTS
1. Good Rubber Essential.––Buy new rubbers every
year, as rubbers deteriorate from one season to another. A good rubber for
cold-pack canning must be such as to stand four hours of continuous boiling
or one hour under 10 pounds of steam pressure. The combination of moist heat
plus acids and mineral matter in vegetables and fruits tends to break down
the rubbers during sterilization. Rubbers kept in a hot or very warm place,
as for example, on a shelf near the kitchen range, will deteriorate in
quality. Be very particular about the rubbers used. Spoilage of canned goods
has been traced frequently to the use of poor rubbers.
Fig. 10. Simple test for rubbers. A perfect rubber will show
no crease or break after being folded tightly several times.
2. Testing Rubbers.––It is always well to test
rubbers when buying. A good rubber will return to its original size when
stretched. It will not crease when bent double and pinched (Fig. 10). It
should fit the neck of the jar snugly. It is cheaper to discard a doubtful
rubber than to lose a jar of canned goods.
Fig. 11. Wire rack for jars.
Vegetables and fruits should be sorted according to color,
size and ripeness. This is called grading. It insures the best pack and
uniformity of flavor and texture to the canned product, which is always
The most important steps in canning are the preliminary
steps of blanching, cold-dipping, packing in hot, clean containers, adding
hot water at once, then immediately half sealing jars and putting into the
sterilizer. Spoilage of products is nearly always due to carelessness in one
of these steps. Blanching is necessary with all vegetables and some fruits.
It insures thorough cleansing and removes objectionable odors and flavors
and excess acids. It starts the flow of coloring matter. It reduces the bulk
of greens and causes shrinkage of fruits, increasing the quantity which may
be packed in a container, which saves storage space.
Blanching consists of plunging the vegetables or fruits into
boiling water or exposing them to steam for a short time. For blanching in
boiling water place them in a wire basket (Fig. 17) or piece of cheesecloth
(Fig. 18). The blanching time varies from one to fifteen minutes, as shown
in the time-table on page 2, and the
products should be kept under water throughout the period. Begin counting
time when the articles are first placed in boiling water or steam.
Spinach and other greens should not be blanched in hot water. They
must be blanched in steam to prevent the loss of mineral salts, volatile
oils and other valuable substances. To do this place them in a colander and
set this into a vessel which has a tightly fitting cover. In this vessel
there should be an inch or two of water, but the water must not be allowed
to touch the greens (Fig. 12). Another method is to suspend the greens in
the closed vessel above an inch or two of water. This may be done in a wire
basket or in cheesecloth. Allow the water to boil in the closed vessel
fifteen minutes. Excellent results are obtained, also, by the use of a steam
cooker or steam pressure canner.
Fig. 12. Use of a colander to blanch greens in steam. The
colander is placed in a receptacle with tightly fitting cover. No water
should touch the greens.
When the blanching is complete remove the vegetables or
fruits from the boiling water or steam and plunge them once or twice into
cold water––the colder the better. This latter process is the Cold Dip. It
hardens the pulp under the skin, so that the products are not injured by
peeling. It also sets the coloring matter. Do not allow the products to
stand in the cold water.
Always blanch and cold-dip only enough product to fill one or two
jars at a time. The blanching and cold-dipping should follow at once when
the vegetable or fruit is prepared, and the packing into jars should
immediately follow the blanching and cold-dip.