USRE13232E - Maker - Google Patents

Description

UNITED STATES PATENT OFFICE.

JAMES ROBINSON HATMAKER, OF PARIS, FRANCE.

DRYING MILK.-

Specification of ReissuedLetters Patent. Reissued May 2, 1911.

No Drawing. 0rigina1 No. 920,952, dated May 11, 1909, Serial No. 324,072. Application for reissue filed August 18, 1910.

To all whom it may concern:

Be it known that I, JAMES ROBINSON HAT- MAKER, a citizen of the United States, residing at Paris, France, have invented new and useful Improvements in Drying Milk, of whichthe following is a specification.

, My present invention is an improvement indrying milk, whereby pure dry milk of improved quality can be obtained.

Heretofore it has been found necessary to modify natural milk preliminary to dry ing it as, for example, by adding thereto foreign substances, in order to prevent the proteids of the milk from. becoming insoluble during the drying process. All the dry milk heretofore made by exposing liquid milk in a thin layer or film upon a surface heated in excess of 212 F. and reducing it to dryness rapidly has been so insoluble in water that the liquid milk reconstituted from it by the addition of water has shown a large deposit of milk constituents within a few minutes, unless the liquid milk from which it was obtained was reduced in acidity by the addition of some neutralizing agent. This fact is too well known in the.art to require further elaboration.

I have discovered that'absolutely pure dry milk of practically natural solubility-from which liquid milk most closely resembling natural milk can be reconstituted'by the simple addition of warm watercan be obtained from pure fresh milk. in. its natural state and without'its being changedvor modified in any way whatever if such natural milk is exposed, in a. very thin film, upon a suitably heated surface, for a period not exceeding two and one-half seconds induration, and thereon reduced to practical dryness and then removed therefrom.

In practice, I- prefer that the milk to be dried shall not remain exposed upon the vheated drying surface for a longer periodv than 2 seconds, and it is preferable in some cases that it should not be exposed more than one-half of a second. Generally speaking, inorder to get the least possible change in the contained proteids, the exposure should be as short as possible. It is very easy to obtain this exceedingly short exposure by employing rapidly-revolving drying cylinders as the drying surfaces, and Iprefer to employ such cylinders, although Serial No. 577,882.

heretofore upon revolving drying cylinders heated in excess of 212 F. being exposed thereon in a thin film or layer, but the rate of revolution of such cylinders when used for that purpose. has been so slow that the film or layer of milk has been exposed thereon much longer than 2% seconds usually from 5 to 10 or more seconds. In the cases where milk has been dried on cylinders placed within a vacuum or a partial vacuum the exposure has usually been for a much longer time than 10 seconds. By drying milk by exposing it upon the heated drying surface for less than 2?; seconds, I effect the operation soquickly that chemical action whereby the proteids in milk are rendered insoluble bythe known processes, cannot take place. I thus obtain pure dry milk of natural acidity and solubility. I find this process of very limited exposure to be es-' pecially valuable also in drying mixtures of milk and other substances such as mixtures of milk and eggs, mixtures of milk and sugar, starch, etc. It is not necessary that the milk to be dried by this process should be previously condensed, although condensed milk can be dried by the process in which case the condensing would, in asense, form a part of the process. With condensed milk, on account of the smaller proportion of water, it will be clear that the material may be dried with a less highly heated surface within the brief period contemplated by my process. I prefer, however, to use milk that is absolutely natural and per fect-ly fresh and that has not been pasteurized or treated physically or chemically in any way. By this I mean that in the preferred manner of carrying on my process the milk is drawn into a film not only in a chemically natural condition, but without previous bciling; thus further distinguishing it in a radical manner from certain crude attempts inwhich the milk is boiled just before the drying step. Such boiling would not only prolong the period of high temperature treatment, but would tend to render the ultimate product indigestible and would be otherwise injurious. Itis, of

' course, to be understood that the expression unboiled milk is used in the following claims in its ordinary sense as denoting milk which has not been previously raised to a temperature of 212 F. If twin-cylinder drying machines are used, the depth of the milk maintained between them should be kept as low as possiblesothat it will not be injuriously affected byover-heating.

The process can be executed upon a single drying cylinder, any suitable means being provided for introducing the milk upon the said cylinder in a thin film and for removing it therefrom within the time specified.- Knives fixed and held in contact with the cylinder, I have found to be the best means for removing the film therefrom.

The time of exposure is the essence of my present invention. The exposure being so very short thetemperature of the drying surface must be maintained above the degree necessary to drive ofl' the water in the exposed film, to the extentdesired, within the time specified. The drying should be effected in the free atmosphere and 'the temperature of the drying surface should be kept above 270 F. for best results, although under certain conditions. good results can be gained with lower temperatures. In practice I have found cylinders heated by-3i: atmospheres of steam pressure to give excellent results The milk being necessarily exposed in a very extended form, as in a thin film, the dry milk obtained is very light and flaky in form. It is distinguishable from the dry milks heretofore made by the fact that it has its natural acidity i. e. the acidity of the natural milk in dry form whereas the dry milk produced from milks which have been reduced in acidity have alower acidity. and a somewhat unnatural taste. This dry milk is not only light and flaky in form and of practically natural solubility but it also has natural acidity and taste. It is also perfectly, sterile.

I claim:

'1. The hereinbefore described process of drying milk which consists in exposing it in a very thin film, for a period of time not exceeding two and one-half seconds, upon a suitable drying surface heated in excess of 270 F.

2. The hereinbefore described process of drying milk whereby absolutely pure sterile dry milk of practically natural solubility and of natural acidity is obtained, the said process consisting in exposing natural liquid milk, in a very thin film, for a period of time not exceeding two and one-half seconds,

upon a suitable drying surface heated in excess of 270 F.

3. The hereinbefore'described process of drying milk which consists in exposing unboiled chemically natural milk in a very thin film, for a period of time not exceeding two and one-half seconds, upon a suitable drying surface-heated to such temperature as substantially to expel the contained water of the milk within the said period of time. 4. The process of reducing milk or other proteid-containing liquids to a dry conservable state, which-consists in exposing it, with its acid unneutralized andfree from added chemical agents, in the form of a very thin filmv-for a period of time not exceeding two and one-half seconds in duration upon a suitable drying surface. heated suflioiently high to reduce it to a dry conservable state within the time of such exposure and forcing said film fromsaid surface.

5. The hereinbefore described process of drying milk of unn'eutralized acidity which consists in first condensing it somewhat and then exposing it in a very thin film for a period of time not exceeding two and onehalf seconds upon a suitable drying surface heated to such temperature as will substantially dry it within said period,

JAMES ROBINSQN HATMAKER.