Improvements in the Method of and Apparatus for Sterilizing Milk.
Year: 1898

page_text: Date of Application, 8th June, 1898-Accepted, 1st Oct., 1898
Improvements in the Method of and Apparatus for Sterilizing Milk.
I, NIELS BENDIXEN, of Hauchs Vej 16, Copenhagen, in the Kingdom of
Denmark. Superintendent of a Laboratory, 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. -
The present invention refers to a method of and apparatus for sterilizing
milk by boiling under such conditions and treatment that all the valuable quali-
ties of fresh milk is retained by the latter.
It is well known that milk, when heated to boiling point assumes a peculiar
taste which considerably reduces its value for use Experiments have been made
to avoid this taste by removing the atmospheric air from the vessel in which the
heating takes place, as it has been correctly presumed that the oxygen plays
an important part in producing this taste, and very satisfactory results have been
obtained this way in ordinary pasteurizing of milk
If, however, in order to obtain a really steile milk, in which the sporuliferous
bacteria are killed, this heating is not sufficient The milk must then be heated
to above the boiling-point as is the case in the present method, but in this case
the boiled taste can not be avoided by a mere exclusion of the atmospheric
oxygen.
The feature of the present invention consists in saturating the milk with
carbonic acid before boiling whereby the atmospheric air is driven out and then
boiling under pressure at a temperature of about 120° Cel In this way the
boiled taste is not only completely avoided, but the milk is not submitted to any
of the ordinary alterations which generally follow with the boiling Thus it does
not form a skin, it is not discoloured, and retains the quality of depositing
cream
Concerning the part taken by the carbonic acid, only more or less reliable pre-
sumptions may be put forward on the basis of experiments performed They,
however, show clearly enough that the exclusion of the oxygen is merely a part
of the total action Under ordinary cucumstances the lime contained in the milk
will during the boiling process presumably cause the formation of changeable
compounds between the said matter and sugar of milk, and these compounds will
decompose by the heat during further alterations is the molecules of the sugar.
If, however, there is a surplus of carbonic acid, this will bind the lime, and the
sugar of milk will remain unaltered in spite of the proportionately great heat.
A similar circumstance will presumably take place as far as regards the albumen,
as it is well-known that phosphate of lime always forms a subordinate part or
attendant of these. Even if reliable results as to the importance of the phos
phate of lime in a chemical sense are missing, its appearance makes it easily
explainable that the carbonic acid may have the result proved by the experiments,
namely to prevent the albumen from changing during the heating process.
[Pena 81

page_text: After the milk, as described, has been boiled under pressure when saturated
with carbonic acid, it is cooled off and is then perfectly sterile. It contains,
however, still carbonic acid, which may be shown by its taste and in order to
restore the latter to that of fresh milk it becomes necessary again to remove the
carbonic acid and to replace it with atmospheric air.
This is performed simply by passing a current of sterile air through the milk.
The air will then partly carry the carbonic acid with it and will be partly
absorbed by the milk until this is saturated therewith as is the case with fresh
milk
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1
In this way it becomes possible to produce a milk, which retains all the quali-
ties of fresh milk and which, moreover, lasts fresh for a long time and may be
used without any danger of contagion; as geims such as tubercle-anthrax and
colibacterie are absolutely destroyed by the boiling under pressure.
In the accompanying drawing I have shown an apparatus for the 'treatment of
milk according to the present invention
'
A is a container for heating and treating the milk with carbonic acid, B-a
cooling apparatus and C a container for removing the carbonic acid by means
of sterilized air for drawing off the milk.
$
The apparatus 18 used in the following manner after all the containers and
tubes have been sterilized by passing steam through them, the milk is poured
through a funnel into the container A which has double walls, while caibonic
acid from any source is lead through the tube having a filter The tube has
two branches & d, the first of these opening into the container A immediately
above the level of the milk, while the other (d) is continued down to the bottom
of the container where it is perforated Through the holes the carbonic acid
passes in small bubbles up through the fluid and escapes together with the atmo-
spheric air through a tube e, the other valves of the container being kept closed.
The filling in of carbonic acid is continued while the fluid is agitated by the
stirier, until pure carbonic acid comes out, and steam 18 then, while the stiring
is continued, lead through the tube a into the interstice between the walls of the
container A The supply of carbonic acid is then shut off, also the outlet tubo e
and the steam supply is continued until the fluid boils The steam which is
developed, escapes through a safety valve f, whose counter-balance decides the
temperature and pressure, which may be read off by a thermometer g and a
manometer h It will generally be preferable to work with a pressure of about
2 atmospheres, which correspond to a temperature of about 120° Cel. To prevent
condensation of the milk during the boiling the steam may also be lead through
a tube to the cooling apparatus B, where it 18 condensed and where the distilled
fluid is kept for subsequent mixing with the bulk of the milk
In ordinary cucumstances it will be best to continue the boiling for half an
hour, but the boiling may, however, if desirable, be prolonged for any time
without danger of altering the milk.
The milk is then lead through the tube to the cooling apparatus B, which
consists of a cooling coil in running water, through which the milk passes over
into another container C
An air tube with filter having two branches in a similar way to the above
mentioned carbonic acid tube to the container A, leads into this airtight container
Through the perforated tube on the bottom of the container the air, passes
through the milk and escapes through a valve n in the covel. The container
is provided with a tube o which has a row of faucets and these are before use
sterilized by steam through the tube p and permit a drawing off of the sterilized
fluid
The air which is brought to the contamer C must, before it passes through
the filter, be purified by allowing it to bubble through cleaning bottles s, filled
with sulphuric acid, soda lye, solution of permanganate of potassium and the
like.
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page_text: 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
—
1 A method of sterilizing milk while retaining all the qualities of fresh milk,
consisting in saturating the milk with carbonic acid and then boiling under
pressure at a temperature of about 120° Cel, then removing the carbonic acid
and saturating it with air by leading a current of atmospheric air through it.
2. An apparatus for carrying out the method described in Claim 1 character-
ized by a closed container A having feeding tubes for carbonic acid, stirrer and
steam-hood, two tubes leading to a cooling apparatus B, one (k) from the upper
part and another (1) from the lower part, so as to lead developed steam or the
treated fluid through the said cooling apparatus to a container C which has an
aur-feeding tube m and a drawing off tube with a row of faucets for drawing off
of the sterilized milk.
Doted this 9th low of Tu.. 1900
HASELTINE, LAKE & Co,
45, Southampton Buildings, London, W.C, Agents for the Applicant.