The Process of Canning Vegetables 
IN America particularly we have become so accus- 
tomed to the preservation of all kinds of foods in 
f^lass or tin that it is difficult to realize how compara- 
tively modern is this process. Yet it is less than a hun- 
dred years since the establishment of the industry, Ezra 
Daggett and Thomas Kensett being credited with pack- 
ing oysters, lobsters and salmon in New York, and Will- 
iam LInderwood and Charles JMitchel preserving fruits in 
Boston, about 1820. Nicholas xAppert, a French confec- 
tioner and chef, is usually regarded as the discoverer of 
the art of canning. The French government having of- 
fered a prize of 12,000 francs for a method of preserving 
foods which would be practicable for army and naval use, 
Appert set to work about 1795, but it was not until 1804 
that he hit upon the essentials of the method, namely, 
heating the jjroduct and hermetically sealing the contain- 
er. Ijy 1810, after innumerable experiments, Appert was 
satisfied with the results and published his method, where- 
upon he was awarded the jirize. Although primarily a 
war measure, the great advantage of being able to pre- 
serve food for indefinite periods was obviously of such 
value that the process was almost immediately applied 
commercially, and to-da}' the annual value of goods can- 
ned in the United States alone exceeds a quarter of a bil- 
lion dollars. 
Appert, of course, worked long before anything was 
definitely known concerning the causes of the spoiling 
of foods, and ascribed his results to the exclusion of the 
outside air. Indeed, Guy Lussac, one of the foremost 
chemists of his time, came to the same conclusion, re- 
porting that decay was due to a series of oxidations and 
that Appert's method, by preventing contact witPi outside 
air, stopped the process. Similar explanations were made 
by other scientists, bitt not until the epoch-making inves- 
tigations of I.ouis Pasteur was the fundamental principle 
discovered that all decay was due primarily to the activity 
of certain microscopic plants — the bacteria. However, 
the original means devised to exclude the air likewise 
excluded or destroyed the bacteria : consequentU', the re- 
sults were satisfactory, regardless of the specific cause of 
the trouble. It may be pointed out, however, that had 
Appert known the real source of the spoiling of foods it 
would not have required fifteen years for him to discover 
the remedy, and that the perfection of the canning indus- 
try has onlv been possible through the knowledge obtained 
from the science of bacteriology. 
Successful canning depends, therefore, upon two 
things : first, the killing of all micro-organisms within the 
can or jar of food, and, second, the sealing of the con- 
tainer so that no bacteria can enter from the outside. 
With the exception of a few fruits and vegetables which, 
upon standing, deteriorate in flavor and consequently are 
not worth preserving, the spoiling of canned foods is en- 
tirelv due to the presence of bacteria. Either the method 
of killing the bacteria, commonly called sterilization, is in- 
adequate, or, this being accomplished, bacteria from the 
outside are ]>ermitted to enter the can during or after 
sealing. Carelessness in closing the jar or can, whereby 
bacteria on the hands or a cloth or some utensil are com- 
municated to the inside of the lid or jar, may result in 
the loss of the contents, even though the container be 
tightly closed afterwards. Of course, any hole or leak 
around the top of a jar, permitting the entrance of the 
decav-producing organisms, will likewise be disastrous — 
hence the use of the rubber ring on glass jars and of seal- 
ing wax, etc., for hermeticall'>- closing cans. Mere clean- 
liness, as the term is jrdinarih' tised in tlie kitchen, is 
not sufficient for the preservation of food in containers. 
Absolute bacteriological cleanliness, the same that is nec- 
essary in the laboratory in the preparation of pure cul- 
tures of beneficial or disease-producing germs, must be 
maintained. 
Fortimately, this is a comparatively simple matter, 
when one thoroughly understands the problem involved. 
While commercial canneries, because of the necessitv of 
accomplishing the process on a large scale in a short space 
of time, are provided with elaborate and expensive ap- 
paratus, just as satisfactory results mav be obtained by 
any householder with ordinary kitchen lUensils. For 
sterilizing a number of jars at a time a wash boiler or 
certain types of ham boilers are admirably adapted. The 
wash boiler should be provided with a simple wire basket 
which will stand up from the bottom of the boiler about 
an inch. The basket should be strong enough to hold the 
weight of a dozen filled jars or cans, and it is usuallv nec- 
essary to strengthen the bottom with wooden strips or 
heavy wire or metal bands. Handles which will permit 
the full basket being lowered and lifted from the boiler 
are also a great convenience. If a wash boiler is not 
available, any sort of a vessel with a tight-fitting lid, 
large enough to contain one or more jars, may be used. 
Recipes for the preparation of the various vegetables 
are easily obtained from any good cook book, and there is 
no need of going into much detail here. Salt is usually 
added, and for some things, like asparagus, soaking in 
water containing lemon juice or vinegar is recommended. 
In general, all that is necessary is to clean and cut the 
raw vegetable into requisite size and pack into the jar, 
covering with cold water. ( )f course, the cleaner the 
jars and lids the better. If glass jars are used, the rub- 
ber ring should invariably be placed at this time and the 
lid put on loosely. About two or three inches of water 
is sufificient to put in the bottom of the boiler. More 
water takes more time and gas, and it is not the water 
which sterilizes, but the steam. .After lowering the 
basket containing the jars into the boiler, and fitting on 
the lid of the boiler tightly, the water is brought to the 
boiling point and the contents subjected to the action of 
steam for one hour. If more jars are to be sterilized, 
remove the basket at the end of the hour, tighten the lids 
of the jars and set aside for 24 hours ; or the boiler with 
its contents may be removed from the stove, and if the 
lid is tight the individual lids of the jars need not be 
tightened at this time. On the second day, repeat the 
process, being sure to loosen the lids previous to steriliza- 
tion and tightening them afterwards, and set aside as 
before. After a second 24-hour period, sterilize again 
for the third and last time. 
The reason for this so-called discontinuous sterilization 
or repetition of the steann'ng three times, after a consid- 
erable interval of cooling, is based upon a knowled,ge 
acquired from long bacteriological experimentation. 
While a single exposure to steam, with a temperature of 
approximately 212° F., will kill most of the bacteria 
ordinarily found on vegetables, certain germs are pro- 
vided with cells or spores which will resist the action of 
even a greater heat. By setting aside for 24 hours, these 
spores grow into a stage which is more easilv attacked 
bv the heat and after the second cooling period and the 
third steaming, the last of these more resistant forms are 
killed. 
Once all the bacteria within the jar are destroyed, it 
but remains to prevent the access of outside eerms. 
This is accomplished by tightly closing or sealing the jar 
by the method provided. It is obvious that no matter 
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