ABSTRACTS
The freezing point of milk. 1. The freezing point
and solids-not-fat content of the milk of indivi-
dual cows throughout a period of lactation.
R. ASCHAFFENBURG AND P. L. TEMPLE (1941).
Jour. Dairy Res. 12, 315
INVESTIGATIONS on the freezing point and solids-not-fat
content of individual samples of milk from three short-
horn cows throughout the greater part of a lactation are
reported. The average values of the freezing point
depressions for the morning milk from three cows were
0.546ºC., 0.546ºC. and 0.544ºC. respectively. For each
animal, the freezing point depressions of the evening
milk was on the average 0.002ºC. higher than that of the
morning milk. The authors have confirmed the remark-
able constancy of the freezing point, and the deviation
less than 2 per cent from the average. The occurrence
of the extreme values for the freezing point depression
(0.529ºC.— 0.560ºC.) were not associated with periods
of coming into season or with service. There is only
slight correlation between the depression in freezing
point and the solids-not-fat. The fluctuations of the
freezing point were not persistent, while those of the
solids-not-fat tended to persist for several days. [C. P. A.]
The effect of pasteurization on some constituents
and properties of goat's milk. H. S. HALLER,
C. J. BABCOCK AND N. R. ELLIS (1941). Tech.
Bull. U. S. Dept. Agric. 1-14
THE authors have studied the effect of holder and
high temperature, short-time (160ºF.) methods of pas-
teurization of morning's milk from a herd consisting
of pure bred and grade Saanen and Toggenburg goats
on the degree of the denaturation of the soluble pro-
teins-albumin and globulin, on the solubility of calcium
and phosphorus, on curd tension, on the keeping quality
and on the amount of reduced ascorbic acid. On the
total of 25 runs made for holder pasteurization, three
temperatures namely 142ºF., 145ºF. and 147ºF. were
used.
H. T. S. T. pasteurization reduced the amount of soluble
calcium and phosphorus by 3.6 and 3.2 per cent res-
pectively. Holder method caused a greater loss of solu-
bility namely 7.5 and 4.7 per cent calcium and phos-
phorus
respectively. This average decrease of the
soluble mineral constituents is less than the normal
variation in calcium and phosphorus content of milk.
H. T. S. T. pasteurization denatured albumin and
globulin by about 7.4 per cent, whereas holder method
denatured an average of 4.8 per cent of the same.
This again is not significant compared to the fluctuations
in the protein content of goat's milk. The curd tension is
reduced considerably (38.4 per cent) by the holder method
and only slightly (5.1 per cent) by the H. T. S. T. pas-
teurization. The increase in temperature of pasteuri-
zation from 142 to 147ºF. produced no definite trend
in curd tension reduction. The bacterial count per ml.
and flavour score (range 0.25) given for raw and pas-
teurized milk for four days revealed that the flavour of
fresh goat's milk is improved slightly and the keeping
quality is improved considerably by both methods of
pasteurization. Holder method of pasteurization causes
a decrease of from 33-45 per cent in the ascorbic acid
content and H. T. S. T. process did not affect the same.
The modified Kay and Graham method and Scharer's-
phosphatase test is found to be unsuitable for detecting
improper pasteurization of goat's milk, unlike cow's
milk. The phosphatase is sufficiently inactivated for
the milk to pass the test as properly pasteurized, when
it had been heated only for 5 minutes at 143ºF. [C. P. A.].
Testing pasteurized cream: H. JENKINS (1941)
Amer. Milk Rev. 3, 59-60
THE author recommends the use of resazurin dye for
testing pasteurized cream, and set out a correlation
between the reduction time of resazurin dye and the
standard plate count of the pasteurized cream. The test
consists in adding 0.1 ml. of 0.05 per cent aqueous
solution of resazurin dye to 10 ml. of pasteurized cream in
sterile test-tubes, previously heated in a water bath
at 98ºF, and incubating at 98ºF. The colour changes
of the resazurin dye are observed at half-hour intervals
and the time required for the colour of the dye to change
from greyish blue to pink is taken as the reduction
time. The author, as the result of numerous experi-
ments, finds out that cream having a reduction time
less than 6 hours often exceeded the prescribed legal
plate count limit of 40,000 bacteria per ml. This is
supported by the customers' complaints whenever the
cream had a reduction time under 6 hours. When the
reduction time of the pasteurized cream was 6-7 hours
it answered the state regulations, prescribing the standard
plate count of 40,000 bacteria per ml. and the customers
had no complaints. It was found out that the cream
having a reduction time of 6-7 hours had an average plate
count of 17,000 bacteria per ml. Finally, the author
recommends that standard plate count may be supplanted
by the resazurin test for testing pasteurized cream. [E.V.S.]
A study of factors influencing the quality of
cultured skim milk or butter milk: F. V.
KOSIKOWSKY AND H. J. BRUECKNER (1941).
Milk Dealer 30, 36-50 ; 71-74.
As a result of the studies to determine the effect of
various factors on the body, amount of whey separa-
tion and flavour of cultured skim milk or butter milk,
the following conclusions are drawn by the author :
1. The viscosity of the cultured skim milk-was directly
related to the acidity at the time of breaking the curd,
showing as the acidity increased the viscosity of the
cultured skim milk became greater.
2. A high acidity produced a heavy body and least
amount of whey separation. Acidities in excess of 0.72-
0.75 per cent were effective in preventing excessive whey
formation.
3. A direct relationship was found between the vis-
cosity of the cultured skim milk and S. N. F. content of the
milk; but at an acidity of 0.70 per cent or lower, no
relationship existed.
4. When milk was standardised to different percentages
of S. N. F., no significant results were produced regarding
whey separation.
5. Pasteurizing the milk at 185ºF. for 30 minutes pro-
duced highest viscosity and least amount of whey separa-
tion, whereas the pasteurization temperature of 150ºF.
for 30 minutes resulted in lowest viscosity and maximum
amount of whey separation. Pasteurization temperatures
of 205ºF. and 170ºF. produced viscosity intermediate to
those between 185ºF. and 150ºF.
336