AN IMPROVED METHOD OR PROCESS OF PURIFYING FAT AND OIL
Year: 1885

page_text: I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake, & Co, Patent Agents
Southampton Buildings in the County of Middlesex do hereby declare the nature
of my invention for "AN IMPROVED METHOD OR PROCESS OF PURIFYING FAT AND
OIL "and in what manner the same is to be performed, to be particularly
described and ascertained in and by the following statement:-
This invention relates to the purification of animal and vegetable fat and oil.
When animal or vegetable fat not having been completely purified, is kept stored
for a considerable time, it undergoes a partial decomposition. If the albuminous
portions such as membranes and other tissues of the raw fat, and the water have
not been completely removed therefrom those matters will become putrid particu-
larly in the presence of air and impart to the 'fat a very disagreeable smell and
taste, and not only this but on account of the putrefaction of the albuminous
portions the fat itself containing these will be attacked, and, so called, fermentative
saponification arise, so that the neutral fat is partially decomposed and fatty acids
and glycerine are formed. The volatile, less carboniferous fatty acids such as
propionic acid, butyric acid, valeric acid, capric acid etc, are principally formed and
small quantities of these having a very disagreeable and strong smell and taste,
render the fat intermixed therewith unfit for food.
Also the more carboniferous acids as stearic acid, palmitic acid, and oleic acid,.
contribute, although not in so high a degree as the acids before mentioned, to render
the fat unfit for the said purpose.
Other circumstances also contribute to render fats unfit for food, namely that in '
the purifying they have been heated to so high a temperature that dry distillation
has partially arisen, or that unfit or too strong chemicals have been used.
As an example of fats of vegetable origin I may mention oils produced by means
of hot pressing, olive-oil, etc. American tallow such as is used in the manufacture of
stearine may be mentioned as a specimen of a fat of animal origin, which through
imperfect purification and subsequent storing is rendered unfit for food.
Not only are such fats sometimes unfit for food but the decomposition has
frequently gone so far that on account of the yield of fatty acid the fat is unfit.
even for machine grease..

page_text: The purification of such fats, (which usually are comparatively cheap), for food
may be effected by means of certain physical and chemical processes in the following
manner.
1 The fat is freed from its volatile impurities. To accomplish this steam super-
heated to 100°-250° C is caused to pass in a finely divided state through the melted
fat for two hours; by this means not only the volatile products arising out of the
putrefaction of the albumen but the fatty acids poor in carbon are easily removed;
a part of the free fatty acids rich in carbon may also be removed, owing to their
property of being capable, unaltered, to distil with superheated steam.
Fats of animal origin, for instance tallow, require the passage of superheated
steam having a temperature of about 200°; some fats of vegetable origin on the
contrary, for instance bad olive-oil, require the steam to have a temperature of 250°
C. at atmospheric pressure. For such fat the most suitable temperature must be
ascertained by experiments.
Experience teaches that the lower the temperature can be kept in the treatment
with superheated steam the better will be the quality of the product.
As volatile substances are generally much more speedily and completely volati-
lized under a vacuum than under pressure, I have caused the above treatinent
with superheated steam to take place under a vacuum, (although this is not
necessary,) whereby the temperatures may be respectively lowered to 150° and
200° C.
The fat thus freed from volatile impurities and which has now lost its disagree-
able odour and taste still contains some non-volatile impurities such as albuminous
and glutinous tissues, particles of metal from the distillation vessel, and other
inorganic matters, very carboniferous fatty acids not previously volatilized, colouring
constituents etc, which must be removed, before the fat may be considered to be
pure.
2nd The fat is freed from the albuminous and glutinous matters, that is to say -
the fat heated to from 80°-100° C. and mechanically stirred by any suitable
contrivance, is caused to come into very intimate contact with any salt of alumina,
for instance alum or sulphate of alumina, baving the property of forming with the
said matters insoluble chemical combinations. Iron salts etc may also be employed
although less advantageously. The melted fat and the solution beneath it having
been left in repose for some hours, the albuminous and the glutinous matters collect
as a deposit between the surfaces of the fluids and are removed.
It may sometimes be advantageous to perform the 2nd operation prior to the first
operation as well as subsequently.
3rd The fat is next freed from its inorganic matters by treating the melted fat,
as previously described in the second operation, with a weak solution of an acid,
preferably sulphuric acid or oxalic acid, and then washing off the surplus with
water.
The 2nd and 3rd operations may take place simultaneously by adding a little
sulphuric acid or oxalic acid to the solution of salts of alumina and then proceeding
as in the second operation.
4th The fat is freed from non-volatilized, free fatty acids by treating the melted
fat in a melted state, either when boiling with steam or when vigourously agitated
by mechanical means, with a solution of any carbonate of alkali or with a carbonate
of any alkaline earth, kept in suspension in water and very finely divided, in such
quantity as will be requisite for the complete neutralization of the free fatty acids.
These matters give, with the nascent, fatty acids, while developing carbonic acid,
alkalies or earths, while the neutral fat is not attacked. The fatty acid earths are
insoluble in water and in neutral fat, and are therefore easy to separate from the
melted fat. The fatty acid alkalies are, on the contrary, soluble in water and are
moreover of such a nature, in a solution as to emulge the fat, wherefore they must
be removed in another way. It is known that fatty acid alkali is insoluble in
concentrated solution of the chlorides and sulphates of the alkalies. If therefore
the treatment of the fat with carbonate of alkali takes place in a concentrated

page_text: solution of common salt, the fatty acid alkali produced thereby detaches itself
undissolved at the same time as formed, and may thus be easily removed from the
melted fat, which thereby becomes entirely neutral.
-
5 The fat is delivered from its colouring and taste giving matters as follows:-
The fat obtained after the preceding operation is first cooled, which is best effected
by causing it to flow down in a fine jet into cold water kept stirred, whereby it is
obtained in a finely divided state. The water is then allowed to flow away from
the fat, which is mixed with from an equal to a double volume of glacial, diluted,
nitric acid of from 2° to 15° B. differing for different fats, whereafter the mass is
uninterruptedly stirred for some hours, in order that the fat may come into contact
with the solution of nitric acid. The temperature of the fluid is preferably kept
at about 0° C. After from 6 to 36 hours the fat becomes white and the taste which
it had no longer exists.
Owing to the low temperature maintained the nitric acid has not been able to
act destructively on the fat itself, but only on the infinitesimal quantities of
colouring and taste imparting matters. The fat is now completely freed from the
nitric acid by washing, which operation is considerably facilitated by adding a
small quantity of soda or lime, whereafter the fat is melted in hot water at a
temperature not exceeding 50°, and now it is so pure, that it may be used as food
for animals. Certain fats, thus purified may even be made fit for food for man.
In lieu of nitric acid other oxidating agents may be used, as soluble chromates,
permanganate, bioxide of hydrogen etc.
Fat prepared in this manner may be stored for a long time without any decom-
position or other injurious action taking place.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed I declare that what
I claim is
The method or process hereinbefore described of purifying fat consisting in
(1) treating the fat with superheated steam at a temperature of from 100° to
250° C. with or without vacuum, whereby volatile matters are removed; then
(2) treating it with a solution of salts of alumina and diluted sulphuric or oxalic
acid, conjointly or separately, in order to remove albuminous or glutinous matters
and metallic impurities; then
(3) treating it with carbonates of alkali or alkaline earths, in order to remove
free nascent fatty acids; and then
(4) treating it cold with diluted nitric acid or other suitable oxidating agents as
chromates, permanganate, bioxide of hydrogen etc, whereby colouring and taste-
imparting matters are removed.
Dated this 14th day of February 1885.
HASELTINE, LAKE & Co.,
For the Applicant.