Method of Packing Food.
Year: 1896

page_text: Date of Application, 21st Dec., 1896-Accepted, 20th Mar., 1897
Method of Packing Food.
CHARLES EDWARD FITZGERALD, M.D. 27 Upper Merrion Street, Dublin
Surgeon Oculist to the Queen in Ireland and GEORGE PRESCOTT Electrical
Engineer and Optician 9 Merrion Row Dublin do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement :-
Heretofore foods which have been "packed "in metallic vessels, or indeed in
vessels of any kind, have lost a large proportion of their value as food because
the prolonged application of heat necessary to preserve them from decomposition,
spoils, in a great measure, the flavouring properties (important salivary excitants),
and, by destroying the bacteria and their spores, deprives the food of other aids to
that sort of decomposition known as digestion.
In foods heretofore packed, if the prolonged heating has not been applied, then
an antiseptic adulterant of some kind has been used, as boric acid, salt, sugar,
sulphurous acid, or the like. Salt or sugar act as preservatives by robbing the
bacteria of water and so retarding their growth. The use of boric-acid is
objectionable, us it retards, and often altogether prevents, the decomposition of
food when introduced into the stomach; and none of these preservatives cau be
subsequently removed from the food without greatly injuring it as such.
Heretofore, foods packed in packing cans have, besides being subjected to
prolonged heating, the air driven out by the formation of steam in the can, which
is then hermetically sealed, thus causing a partial vacuum when the can cools,
fresh air and any bacteria which it might contain being thus excluded from
the can.
The objects of our invention are:-
1. To pack foods so that they will preserve successfully without the addition of
any antiseptic adulterant, except such as will be automatically dissipated upon the
opening of the can.
2. To retain the natural juices of the food by avoiding a prolonged application
of heat.
3. To avoid the application of so much heat as will burst the capsules of the
spores.
4. To attain the above objects inexpensively.
In order to carry our invention into effect we have provided a packing can which
differs from other packing cans heretofore in use: for whereas these are devised to
sustain an external pressure of the atmosphere, ours, on the contrary, is intended
to bear an internal pressure of several atmospheres.
Our cans are made of tinned steel plate, the body being cylindric and the ends
preferably hemispherical. At one end is a. small hole and a valve opening
inwards. The end with the valve is attached to the body; the other end is not
soldered until the food is introduced.
While the food is being packed the can is held valve end downwards, the valve,
which is much larger in diameter than the opening, having been adjusted in
position; the food is pressed against the valve, keeping it home, and the end is
then soldered on.
The can is now subjected to such a temperature as will kill the bacteria but not
their spores, and the heat is withdrawn. According as the cans become cool there
is injected, through the small opening, aerated blood, water, gravy, oil, or carbon
Price 8d 1

page_text: binoxide, and the injection is continued until the internal pressure is sufficient to
keep the spores in suspension. This injection is effected from the outside through
the opening closed from within by the valve sufficient pressure being exerted upon
the injected medium, which may be antiseptic, in the case of certain kinds of foods,
to cause it to force the valve inwards. The pressure exerted outwardly by this
injected medium operates also in forcing said valve against said opening so as to
close the same and thus hermetically seal the contents.
The valve is a simple disc of thin metal and such a valve has advantages over
those having carefully fitted seats and guides, unless these be made of a strength
that is objectionable and expensive; because the end of the can, even if
hemispherical in form, alters its shape when subjected to internal pressure, such
alteration disturbing the adjustment of the valve and thus setting up leakage.
Again, valves consisting of glass balls on rubber seatings are unsatisfactory, for
the reason that shreds of food are liable to be blown between the ball and rubber,
and, unlike liquids, are not squeezed out; these shreds, although apparently
impervious, permit diffusion to occur through their tissue, and in time the internal
pressure becomes so low that the spores burst into life and thus defeat the main
object.
For the same reason neither cork nor wood are permissible in connection with
the valve, these substances being pervious to diffusion.
On the other hand a thin impermeable disc of metal, much larger in diameter than
the hole it is intended to cover, adapts itself to the changing shape of the end of
the can at the opening. The shape of the latter changing as it does because of
the varying temperatures and pressure. Such disc acts more perfectly when
untrammelled by guides or such like, inasmuch as it is then free to automatically
adjust itself, being thin and flexible, to points of least resistance.
Such a disc acts as a baffle to shreds of food, and, being much larger than the
small opening at the end of the can, thus' differs from valves with ground seatings,
or with glass balls and rubber rings, which have their points of contact exposed,
so to speak, to the contents of the can, the sharp edges of the disc acting as a trap
for any stray shreds blowing in that direction, owing to any blow back during the
process of injection.
Having now particularly described the nature of our invention and in what
manner the same is to be performed we declare that what we claim is :-
1. A method of packing food by partially sterilising same and enclosing it,
hermetically sealed, in a packing can under an internal pressure with aerated
blood, gravy, water, or oil, substantially, as described.
2. A method of packing food by partially sterilising same and enclosing it,
hermetically sealed, in a packing can under an internal pressure with aerated blood,
gravy, water, oil or carbon binoxide, substantially as described.
3. A method of packing food by heating same sufficiently to kill the bacteria,
but not the spores, and sealing the food in a packing can, and injecting into said
can aerated blood, gravy, water or oil until the internal pressure is sufficient to
prevent the growth of the spores, and hermetically closing the can substantially as
described.
4. A method of packing food by enclosing same in a packing can and heating
the food until the bacteria are killed, but not the spores, injecting into the can
aerated blood, gravy, water, oil, or carbon binoxide, until the internal pressure is
sufficient to prevent the growth of the spores, and hermetically sealing the can
substantially as described.
Dated this 1st day of December 1906
CHARLES EDWARD FITZGERALD, M.D.
GEORGE PRESCOTT.