IMPROVEMENTS IN PRESERVING MILK Fruit AND OTHER ORGANIC SUBSTANCES PROAL
Year: 1883

page_text: LETTERS PATENT to Walter Henry Thew of Waterloo in the county of
Lancaster for an Invention of "IMPROVEMENTS IN PRESERVING MILK Fruit
AND OTHER ORGANIC SUBSTANCES
PROVISIONAL SPECIFICATION left by the said Walter Henry Thew at
the Office of the Commissioners of Patents on the 20th June 1883.
WALTER HENRY THEW of Waterloo in the County of Lancaster "IMPROVEMENTS
IN PRESERVING MILK, FRUIT OR OTHER ORGANIC SUBSTANCES
"
This process is conceived to preserve milk, fruits and other organic liquids,
semi-liquids, and solids of animal and vegetable origin for use as foods or other
purposes without the use of chemicals, antiseptics or other added matter and also
without the high heating now employed. This high heating usually affecting the
flavour and appearance of the substance to be preserved and often inducing
chemical changes which more or less reduce the value of the preserved matter.
It has been found that the gerins, organisms or bodies capable of producing
decay, putrefaction, fermentation or such like action (hereinafter called broadly
germs) at a certain stage of their development perish at a temperature or are
sterilized at a temperature comparatively low when compared with that now used
for preservative purposes. The grand difference in fact between the old method
and mine is this. The old method by excessive heat killed the germs outright at
one operation. mine develops the germ and then destroys or sterilizes it at its
most sensitive stage. The easiest method of developing being the mere keeping
of the material at a temperature most conducive to the growth of the germs and
that of killing the developed germ heating the material for a short time to a degree
sufficient to kill or sterilize the organism. I therefore heat the substance to a
temperature of say 140° to 180° Fahrenheit and then keep it for a certain number
of hours at a temperature favorable for germ development when a second heating
takes place sterilizing the second crop of germs.
These alternations of temperature are continued for a length of time found
necessary according to the nature of the substance to be preserved and other causes
until finally all the germs are developed and destroyed or sterilized,

page_text: This method of fractional sterilization is best performed on substances in vessels
hermetically scaled, but in some instances I may use instead, vessels closed against
the outer air by stoppers of cotton wool or other materials which entangles
and prevents from entrance within the Vessel any germs that may exist in this
outer air.
Milk I preserve either condensed or in its natural state in tin glass or other
Vessels Practically I find the following method most suitable; milk is first
condensed by evaporation under an existing method, water only being withdrawn
and no sugar, antiseptic or chemical matter being added. This condensed milk I
place in vessels. (by preference of tin) hermetically sealing same. The tins 1
when filled are placed in a water bath and warmed to a temperature between
130 degrees Fahrenheit-and-180-degrees-according_to_the_season_of_the_year and
the consistency of the milk and other causes. For the same reasons these warmings
last from 30 minutes to 2 hours I do not bind myself however to the particular
heats or durations herein mentioned as different species of germs require different 1
beats to kill them and take longer or shorter time in germinating.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Walter Henry Thew in the Great Seal Patent Office on the
19th December 1883.
WALTER HENRY THEW of Waterloo in the County of Lancaster IMPROVEMENTS
IN PRESERVING MILK, FRUIT, AND OTHER ORGANIC SUBSTANCES."
The processes of decay, putrefaction and fermentation have been shown to be
dependent upon the development of specific organisms. The methods hitherto
employed for the preservation of substances subject to such processes of decay;
putrefaction, fermentation etcetera have consisted in general cither in the addition
to them of chemical agents exerting an antiseptic or preservative action or in
depriving them by desiccation of all water, or in subjecting the substance to be
preserved to a high temperature, the object being to destroy outright all specific
organisms, or their germs, which may be present.
As the latter often resist high temporatures when the process of preserving by.
means of heat. only has been adopted, the temperature to which the substance has
been subjected has necessarily been very high.
My process consists―
1stly. In subjecting the substance to be preserved and which is contained in a
tin or other suitable germ-proof vessel, to a temperature which is sufficient to kill
the fully developed organisms and which varies in different cases between
150 degrees and 200 degrees Fahrenheit and keeping it at this temperature for a
period of between one and two hours.
2ndly. In allowing the heated vessel to cool to the mean temperature of dwelling
rooms (about 60 degrees Fahrenheit.)
3rdly. In repeating these alternate processes of heating and cooling at intervals
of between twelve to twenty four hours, for a number of times depending upon
the substance to be preserved, but which usually is not less than five times.
4thly. In some cases I complete the process by subjecting the substance to be
preserved to a temperature of about 180 degrees Fahrenheit for a longer period
than on the occasion of the previous heatings, that is for periods varying between
two or four hours.
The theory of the process is the following: The more fully developed organisms
which are the immediate cause of the fermentations and decompositions to be
prevented are killed by the repeated and lengthened exposures to 150 degrees or to
180 degrees Fahrenheit. In the times which elapse whilst the substance is cooling
from this temperature to that of the air, or which elapse during the heating up of
the substance from the ordinary temperature to 150 degrees or to 180 degrees
Fahrenheit the germs yet unacted upon are exposed to temperatures most conducive
to their development, and developing become amenable to the destructive action
of temperatures of 150 degrees and 180 degrees Fahrenheit.
The successive heatings and coolings cause the development and subsequent
destruction of successive broods of germs until finally the substance is effectually
sterilized, that is to say freed from all organisms or the germs of organisms
capable of initiating decay putrefaction, fermentation or such like processes.
Milk I preserve as follows:-The liquid in as pure a condition as possible is
condensed to about one third or one fourth its volume and the condensed liquid is
transferred to tins or other suitable vessels which by means of boiling water or
steam have been deprived of any germs they may accidentally be contaminated
with and which are then hermetically sealed.
The milk is then raised to temperatures of 160 degrees to 170 degrees Fahrenheit
and kept at that temperature for an hour and a half or two hours. The milk is then
:

page_text: cooled to 60 degrees Fahrenheit after an interval of 24 hours the process is
repeated. These alternate heatings and coolings are repeated as often as seven
times, the milk being on the last occasion kept at a temperature of 180 degrees
Fahrenheit for two hours. Although I do not employ as an essential element in
my process any chemical substance to preserve the liquid from decomposition, yet
I wish it to be understood that in cases where decomposition or fermentation bas
begun it is expedient to combine the use of those antiseptic agents which are found
to delay the decomposition of milk, amongst which I would name particularly
boracic acid salicylic acid and benzoic acid, with my method of repeated heatings.
The chemical agent in this case prevents the decomposition of the milk occurring
during the initial "heating and before the already fully developed germs have been
-sterilized.-
Although I have referred to particular temperatures and-to-definite-numbers_of
times of heating, I wish it to be understood that I do not bind myself by these
but consider that my invention consists in the employment of successive acts of
heating and cooling in germ proof receptacles for the preservation of organic
decomposable substances substantially as described..
In witness whereof. I the said Waltor. Henry Thew have hereunto set my hand
and seal this eighteenth day of December in the year of our Lord one, thousand
eight hundred and eighty three,
./
I
WALTER H THEW (LS) '