IMPROVEMENTS IN PRESERVING SUBSTANCES FOR FOOD
Year: 1867

page_text: LETTERS PATENT to James Dewar, Doctor of Medicine, residing in
Kirkcaldy, in the County of Fife, in North Britain, for the Invention of
Sealed the 1st October 1867, and dated the 2nd August 1867.
PROVISIONAL SPECIFICATION left by the said James Dewar at the Office
of the Commissioners of Patents, with bis Petition, on the 2nd August
1867.
I, JAMES DEWAR, Doctor of Medicine, residing in Kirkcaldy, in the County
of Fife, in North Britain, do hereby declare the nature of the said Invention
for "IMPROVEMENTS IN PRESERVING SUBSTANCES FOR FOOD," to be as follows:-
My Invention consists in subjecting meat, fish, game, poultry, and eggs to
the action of sulphurous acid for the purpose of preserving them in a condition
suitable for food. The substance to be preserved (other than eggs) is
immersed in sulphurous acid, which may be either of the strength indicated in
the British Pharmacopoeia or diluted with water. Sulphurous acid of the
strength above specified diluted with an equal bulk of water forms an advan-
tageous mixture for the purpose. The substance to be preserved should be
kept so immersed until near the time when it is required to be used for food,

page_text: in a cask, case, jar, or other vessel, closed and as nearly air-tight as
conveniently may be, with the object of preventing the loss of the acid by
leakage or evaporation; or, the surfaces of the substance to be preserved may
be coated with a mixture of sulphurous acid and mucilage, either by dipping
the substance in the mixture or by applying the mixture with a brush or
otherwise to the surfaces of the substance. The sulphurous acid may be of
the strength intimated in the British Pharmacopoeia; the mucilage may be of
gelatine, gum, or starch of a consistency similar to that of the mucilage of
gum arabic indicated in the British Pharmacopoeia, and the acid and mucilage
may conveniently be mixed in equal parts by measure. The coating should
be dried as speedily as conveniently may be; this will be best accomplished by
the application of beat, or by exposure to a current of hot or cold air. Where
the substance is to be preserved for any length of time it is advisable to
repeat the coating several times.
For the preservation of eggs I employ the last-mentioned mode, and instead
of drying the coating and repeating the process as above mentioned it is
better to cover the coating with flour before it dries.
SPECIFICATION in pursuance of the conditions of the Letters Patent, filed
by the said James Dewar in the Great Seal Patent Office on the 31st
January 1868.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I JAMES
DEWAR, Doctor of Medicine, residing in Kirkcaldy, in the County of Fife, in
North Britain, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her Letters
Patent, bearing date the Second day of August, in the year of our Lord
One thousand eight hundred and sixty-seven, in the thirty-first year of Her
reign, did, for Herself, Her heirs and successors, give and grant unto me
the, said James Dewar, Her special licence that I, the said James Dewar,
my executors, administrators, and assigns, or. such others. as 1, the said
James Dewar, my executors, administrators, and assigns, should at any time
agree with, and no others, from time to time and at all, times. thereafter
during the term therein expressed, should and lawfully might, make, use,
exercise, and vend, within the United Kingdom of Great Britain and Ireland,
-the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS IN
.PRESERVING SUBSTANCES FOR FOOD," upon the condition (amongst others) that
I, the said James Dewar, my.executors or administrators, by. an instrument

page_text: ticularly describe and ascertain the nature_of_the_said Invention; and in
what manner the same was to be performed, and cause the same to be
filed in the Great Seal Patent Office within six calendar months.next and
immediately after the date of the said Letters Patent.
NOW KNOW YE, that I, the said James Dewar, do hereby declare the
nature of my said Invention, and in what manner the same is to be performed,
to be particularly described and ascertained in and by the following statement
(that is to say):-
-
.
The nature of my Invention is to preserve meat, fish, game, poultry, and
eggs in a condition suitable for food, for a length of time, by subjecting these
several substances to the action of an aqueous solution of sulphurous acid, in the
manner herein-after described. The property in sulphurous acid of preserving
animal substances from decay has been long known, but no effectual and
useful mode of applying that property to the preservation of such substances
for food has been heretofore ascertained and made known. This has probably
arisen from Inventors having been afraid to make use of a sufficiently strong
solution of the acid, or to expose the substances sufficiently to its action, under,
the notion that to employ a solution of the acid strong enough and for a
sufficient length of time to secure the desired result would render the substances
unsuitable for food or disagreeable to the palate. This apprehension I have
ascertained to be groundless, and I employ a much stronger solution of the.
acid, and expose the substances to be preserved to the action of that acid
solution for a sufficient length of time to secure the desired result. By this
improvement in applying the preservative property of the acid I have succeeded
in effecting complete preservation of the substances before mentioned for the
purposes of food..
The manner in which my Invention is to be performed is as follows:-The
sulphurous acid to which I subject the substance intended to be preserved is
an aqueous solution of ordinary commercial strength, say, of specific gravity
about 1.012, which solution may be diluted with water or with mucilage, or
may be used without dilution, all as herein-after mentioned. When water is
used for diluting the acid I find it best to employ water recently distilled or
recently boiled and allowed to cool. When mucilage is used for diluting the
acid the mucilage which I employ is composed of gelatine, gum arabic,
dextrine, or starch (dissolved in water distilled or boiled as above mentioned)
of a consistency similar to that of the mucilage of gum arabic, otherwise gum
acacia, as indicated in the British Pharmacopoeia.
For preserving, birds, fish, and other animals, I proceed as follows:-The

page_text: feathers of birds and the skins of other animals, except fish, are taken off,
and all viscera are removed, and the substance to be preserved is thoroughly
cleansed from impurities. The bodies of animals thus prepared may be
preserved without being divided into joints or pieces, but in the case of larger
animals I divide them for convenience into suitable pieces or joints. When
the solution is used without mucilage I immerse the substance intended to be
preserved in the solution contained in a case, cask, jar, or other vessel, and
keep it so immersed until shortly before it is required for use; or, as I now
prefer, I allow the substance to be well soaked in the solution, that is to say,
for a period varying from under one to about twenty-four hours, according to
the size of the substance immersed, and then run off the liquid, and leave the
substance in the vessel in a moist state. For example, a beef steak would
require about an hour, a larger substance would require a longer immersion in
proportion to its bulk and solidity, while a very small substance such as an
oyster, prawn, or whitebait need not remain immersed longer than for a few
minutes. The sulphurous acid in which the substances are immersed may
according to my Invention be diluted to the extent of three parts of water to
one part of acid, but I prefer that it should not be diluted further than two
parts of water to one part of acid. If the liquor is to be run off as before
mentioned it is advantageous to use a larger proportion of the acid and make
the liquor of equal parts of acid and water. The sulphurous acid may be
used without dilution, but the liquor in equal proportions of acid and water
is more economical and quite sufficient. When the liquor is composed of acid
and mucilage the substance intended to be preserved may either be dipped
into that liquor and allowed to remain therein for about an hour, after which
it should be taken out and the liquor allowed to dry on its surfaces; or if the
substance be small and all its parts easily reached the liquor may be applied to
it with a brush, so as to give a complete coating to the surfaces of the substance,
and when the coating has dried it is advantageous to give another coating,
and so on until all cracks are filled up and a complete coating is secured.
The substance should then be kept in a dry place to preserve the coating from
injury. The best proportions of acid and mucilage I have found to be equal parts
of each, and the substance may advantageously be immersed in the acid solution
before described previously to its being dipped in the mucilaginous liquor.
To prepare for cooking the substance preserved by any of the modes above
mentioned I steep it thoroughly in water, with a view to removing the acid which
it has absorbed as well as to restoring the moisture which it may have lost.
For preserving eggs I dip them in or otherwise cover them with 'a
coating composed of a mixture of the sulphurous acid and mucilage in

page_text: qual parts of each, and then cover that coating-with-flour, oatmeal,-or-
owdered clay before it dries. -
In witness whereof, I, the said James Dewar, have hereunto set my
hand and seal, this Thirtieth day of January, in the year of our Lord
One thousand eight hundred and sixty-eight.
JAMES DEWAR. (L.S.)