An Improved Process of Preserving Milk.
Year: 1897

page_text: Date of Application, 1st May, 1897-Accepted, 17th July, 1897
COMPLETE SPECIFICATION.
An Improved Process of Preserving Milk.
I WILLIAM TULLIBARDINE MURRAY of "Underwood," Wallacetown, Southland,
New Zealand, at present of 37, Lingfield Road, Wimbledon, London, S.W.,
Manufacturer, 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 :-
Milk is preserved usually by concentration, plus the addition of sugar in large
quantities, and forms the condensed milk of commerce, or, by concentration, plus the
addition of boracic acid or other similar preservatives.
A combination of glycerine and boracic acid has also been recommended. These
methods are open to objection, in the one case, in that the large amount of sugar
foreign to the true character of the milk, especially for the use of infants, and, in the
the other case, in that boracic is foreign to the human system, and, on that account,
objected to by the medical faculty.
My improved process does away with both these objections, and employs an
antiseptic, which in itself is a valuable food, and one which is given to invalids, and
enters naturally into the composition of the human body. This antiseptic
is glycerine, and I have discovered that it, alone, in conjunction with concentration of
the milk, is capable of preserving the latter for a considerable period, without
requiring to be hermetically sealed.
In carrying out my process, I first bring a quantity of pure fresh milk to the
boiling point,-212° F., and then concentrate the same by evaporation, in shallow
pans, or in vacuo, to about one fourth or one fifth of its original volume, having
previously added thereto a certain proportion of glycerine mixed with some five times
its volume of distilled water. To particularize, I take, say, 100 pounds of pure fresh
milk, and add thereto from one half pound to one and one-half pound of ordinary
glycerine (known in chemistry as propyl glycerine), mixed with about four or five
times its volume of distilled water, and then concentrate or reduce the liquid mixture
of milk, glycerine, and water, to about one fourth or one fifth its volume, thus
obtaining the desired product, which has about the consistency of thick cream. The
said product has every desired quality, namely; concentration, or small volume ;
absence of any undue quantity of saccharine matter; freedom of all injurious germ
life; and capacity for keeping for a considerable period, in even the hottest climate;
and perfect adaptation for redilution with water to form a thin liquid, not to be
distinguished from the fresh milk.
In further detail, I will state, that water is added to the glycerine in order to
prevent the coagulation of the milk, which might result from the use of undiluted
glycerine. While I prefer to add the mixed glycerine and water to the milk before
concentration, it is possible to concentrate the milk first, and add them subsequently.
Hence, I do not restrict my claim to the first named order of combining the
ingredients of my improved product.
Further, while I prefer the degree of concentration and the proportions of
elements before stated, I do not restrict my process thereto, since both such degree
and proportions may be varied within certain limits, and still produce a measurably

page_text: good result. The proportion of water added to the glycerine may be widely varied,
since the water is subsequently evaporated.
My improved product will keep, or preserve its original qualities, for a period
varying from two to three weeks, which meets all practical requirements of the
fresh milk trade, as distinguished from the trade in the condensed or concentrated
milk.
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. The improved process of preserving milk, above described, which consists in
bringing a quantity of fresh milk to the boiling point, and then adding glycerine
in the proportion of about one half to one and a half pound of glycerine to one
hundred pounds of the milk, and then evaporating the mixture in vacuo, until it is
reduced to about one fourth or one fifth its volume, as described.
2. The improved process of preserving milk, which consists in the following steps;
1st, bringing a quantity of fresh milk to the boiling point; 2nd, adding glycerine
and pure water in the proportions of about one half to one and a half pound of
glycerine, and several times its volume of water, to one hundred pounds of the milk;
and 3rd, concentrating such mixture by heating it in vacuo to about one fourth or
fifth of its volume, as set forth.