Dried milk powder: a review of British experience ..

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UNITED STATES PUBLIC HEALTH SERVICE |
~ RUPERT BLUE, SurcEON GENERAL

DRIED MILK POWDER

A REVIEW OF BRITISH EXPERIENCE

REPRINT No. 473
FROM THE

PUBLIC HEALTH REPORTS

JUNE 28, 1918
(Pages 1052-1055 )

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WASHINGTON
GOVERNMENT PRINTING OFFICE
1918 :

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uct «23 196

DRIED MILK POWDER.
A REVIEW OF BRITISH EXPERIENCE.!

The local Government board of Great Britain has recently issued a
series of reports under the general classification “Food Reports
No. 24” upon the preparation, composition, and nutritive values of
dried milk powders, with special reference to their use in infant
feeding. It is stated that this article is coming into rather large use
in the preparation of certain foodstuffs and in the feeding of infants.
In view of these facts and of certain claims which have been made
as to the advantages of this product over ordinary cow’s milk,
especially from the point of view of freedom from bacteria of a
dangerous sort, a somewhat extensive inquiry into the entire sub-
ject has been deemed advisable.

History, Manufacture, and Uses.

The first branch of this inquiry related to the use of dried milk
in infant feeding and was carried out by Dr. F. J. H. Coutts with the
assistance of Prof. Delépine. A brief history of dried milk and of
its methods of preparation is first given. It is stated that as early
as 1868 “‘desiccated milk”’ was an article of commerce. Since that
time, and especially during the past 20 years, considerable advance
has been made in the methods of preparation, the general purpose
being to secure a dry residue by evaporation at the lowest possible
temperature and in the shortest time. Most of the processes
employed use one or another form of revolving heated drum, upon
the surface of which a thin milk layer is spread and from which the
dried product isscraped. The most recent processes inject a stream of
partially condensed milk into a heated chamber in the form of a
fine spray, the evaporation taking place in the air and the dry
powder falling to the floor. In the factories the conditions of manu-
facture, as regards general cleanliness, were found to be excellent.
The author, however, does not agree with the commonly expressed
view of the desirability of small-scale manufacture upon the farm.
He found in many such cases that the most elementary precautions
as to cleanliness were being neglected. The importance of placing
this industry under the supervision and control of public health
officials is emphasized. About 5,000,000 pounds of milk powder
were imported into England during 1915 of which one-half came

1 Reprint from the Public Heaith Reports, vol. 33, No. 26, June 28, 1918, pp. 1052-1055.
72765°—18 3

4 DRIED MILK POWDER.

from the United States, and the importance of some form of guarantee
as to the conditions of manufacture of imported products is also
noted.

The market product is of three main varieties, namely, full-cream,
half cream, and skimmed. Certain firms, however, make other
preparations, including some with additional cream. Certain prepa-
rations also contain added cane sugar. .

Dried milk is used as a basis of certain proprietary infant foods, ©
It is also employed in admixture with cocoa and sugar, with egg
powder and sugar as a custard powder, and in various other combi-
nations. Dried milk is said to be used extensively in many of the
industries, particularly in the baking and confectionery trades.
Reference is also made to a so-called synthetic dried milk made
entirely from vegetable materials. The use of the word milk in this
connection is considered rather unfortunate. The ethics of labeling
and advertisement are discussed, and the investigations showed on
the whole a reasonable regard to accuracy, although in some instances
advertisements were decidedly objectionable.

Physical and Chemical Characteristics.

The literature on the physical and chemical characteristics of
milk powders is quoted at length. Dr. Monier-Williams reported
in 1909 upon a sample of whole milk powder, dried upon a drum at.
100°+,C. Upon mixing with a small amount of water, stirring until
homogeneous, and then adding cold, previously boiled, distilled water
to make a 12.5 per cent solution, a product was obtained which did
not have the homogeneous appearance of fresh milk. It had a
slight smell of boiled milk and the fat separated quickly as a yellow
layer at the surface. The curd produced by rennet was flocculent
and finely divided; that produced by acetic acid was similar to that
produced from normal milk. The reconstituted milk did not con-
tain the active enzymes of fresh milk as shown by the peroxydase:
reaction. The fat globules viewed under the microscope were in
most eases larger than those in fresh milk and there was observed a
considerable amount of undissolved proteid. A considerable pro-
portion of the lactalbumen had been converted into a form insoluble
in magnesium sulphate. The milk sugar had undergone no altera-
tion. A somewhat extensive compilation of various analyses of
milk powders is given. Among the foreign substances found are
cane sugar, bicarbonate of soda, various preservatives, coloring
matter, starch, foreign fat, dirt, and traces of certain metals.

Bacteriology.

A similar comprehensive review of the literature of the bacteriology
of dried milk is given. In view of the small amount of information

DRIED MILK POWDER. 5

available, a further investigation was made by the author and 42
samples of commercial preparations were submitted to the Lister
Institute. Ten per cent solutions of the powder showed aérobic
bacteria growing at 22°C., ranging in numbers from 100 to 757,000 per
cc. and at 37°C., from 100 to 892,000 perce. © The results for the most
part, however, ranged under 10,000 per cc. in each case. The
presence of streptococci, enteriditis, and B. coli was recorded in many
of the samples. There was no evidence of tuberculosis in guinea
pigs inoculated from these samples.

Investigations made at the factory indicated an enormous reduction
in bacteria during the process of drying and a subsequent recon-
tamination during handling and packing. The experiment was
tried of running through the drying process a specimen of milk from
a tubercular cow and one heavily inoculated with a potato culture of
tubercle bacilli. Subsequent inoculations of guinea pigs indicated
that living tubercle bacilli may survive the process of manufacture of
dried milk, but “the course of the disease produced by the bacteria
was very much slower than that of the disease produced in guinea
pigs inoculated with the same amount of untreated tubercular
milk.’’ No evidence of tubercular infection was obtained by feeding
experiments upon four young rabbits.

Infant Feeding:

Upon the basis of a review of the experience of many authorities
and of information obtained by personal visits to several large infant
feedings stations, the opinion is expressed that when breast feeding
is impossible dried milk is a very valuable food for infant feeding.
This statement applies, however, only to milk of recent manufacture,
made from a good quality of cow’s milk under hygienic conditions.
It*is probably no better than and perhaps slightly inferior to fresh
cow’s milk, but under the present conditions in cities, and especially
in hot weather, it is often desirable to use it in preference to the latter,
and this can be safely done without fear of prejudicing the health and
progress of the infant. Many infants suffering from digestive
troubles show excellent progress on dried milk. Scurvy and rickets
are rare in infants fed on this preparation, although the occasional
use of fruit juice is desirable.

Increasingly large quantities of milk powder are being used in mater-
nity and child welfare stations supported by public health authorities
and voluntary agencies in England and Wales. A list is given of some
75 districts, including some of the principal cities of Great Britain, in
which this is the case. At Leicester a dried-milk depot is open every
day and consultations are held twice each week. The milk powder is
supplied in packages with directions and in three grades, namely, full
cream, three-quarters cream, and half cream. The very poor obtain

6 DRIED MILK POWDER.

this material at less than cost or even free, while the average pur-
chaser pays a slight margin of profit. Similar details of the opera-
tion of some of the other large welfare stations are given.

For administrative purposes, under the ‘‘Sale of food and drugs
act,”’ milk powders are classed with condensed milk. An extensive
bibliography closes the section.

Nutritive Value.

This section is a report of the investigation conducted by George
Winfield, M. A., on behalf of the medical research committee. The
conclusions are based in part upon observations at infant welfare
centers in Leeds and Sheffield and in part on animal feeding experi-
ments. The growth curvesof children fed exclusively upon dried milk
from birth closely resemble the average growth curve of breast-fed
children, although at somewhat lower levels by reason of the more
delicate condition of these children. The conclusion is reached ‘‘ that
cow’s milk, during the process of desiccation, loses none of the
characters which are necessary for the support of normal growth in
infants.” Teething and walking begin at normal ages, and there is
no greater lability of rickets and scurvy. The experiments on rats —
led to the conclusion that dried milk as a sole food maintains an
animal in good health and permits normal growth for periods which
long outlast those corresponding with infancy and early childhood in
the human subject.

Examination of Milk Powders.

This section of the report, prepared by Sir James Dobbie, Govern-
ment chemist, presents in detail the methods of chemical examination
employed and the analytical results obtained upon a large number of
commercial samples of all sorts. These results are summarized in
Dr. Coutts’s report.

O

T.

PAT. FAN. 21, 1908

syracuse, iv

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