The alcohol test as a means of determining quality of milk for condenseries

ee
UMP

13

UNITED STATES DEPARTMENT OF AGRICULTURE
BULLETIN No. 944 {
Contribution from the Bureau of Animal Industry
JOHN R. MOHKLER, Chief
JnEEnEE ne enn nn ne UE EEEEIUE EEE NEESER
Washingion, D. C. Vv May 12, 1921

THE ALCOHOL TEST AS A MEANS OF DETERMIN-
ING QUALITY OF MILK FOR CONDENSERIES.

By A. O. Danceerc and H. S. GARNER, Research Laboratories, Dairy Division.

CONTENTS.
Page Page
Review of previous work_____----~ 1 | Experiments at condenseries______~
asi imetnods: 1Ssec™. + — == +9. 2 Workat. Bactoiny «A. = =. = 9
Experiments at Grove City creamery_ 4 Work at Hactory. be. =* sno oe 11
Comparison of acidity and alcohol Conelusidns:)U We 5 es Ps) see ee 13
tests of milk for condensing__ 4 Listvot references: = 22-2 13
Relative value of acidity and alco-
Tete S| SGI a EI 8

REVIEW OF PREVIOUS WORK.

_ The urgent necessity for some means of determining the quality
of milk received at condenseries and- other dairy manufacturing
plants has resulted in the continued use of the acid test even aiter
its defects have become generally recognized. This test is based on
the assumption that a titratable acidity above the normal for fresh
milk indicates an increase in acidity due to bacterial action.

It is well known, however, that a certain part of the alkali added
to milk to obtain an end point with any given indicator is combined
with constituents of the milk other than the acids. While this has
been recognized it has not been generally realized how great a varia-
tion in the apparent acidity may be due to this cause. It has been
recently pointed out by Rice (1)* that the casein and the phosphates
both combine with alkali and are subject to a sufficient variation to
cause in some instances an apparent high acidity in fresh milk.

Our own experience, which is not unusual, has shown that not
infrequently milk rejected because of high acidity was fresh milk
in which bacterial action was highly improbable. In making evapo-
rated milk the most essential characteristic is the ability of the milk

1See list of references at end of bulletin.
27179°—21

2 BULLETIN 944, U. S. DEPARTMENT OF AGRICULTURE.

to withstand a temperature sufficiently high to insure the subsequent
sterilization without causing an objectionable curd. While it is as-
sumed, and no doubt correctly, that acidity is an important factor
in determining the coagulating point of concentrated milk, it is by
no means certain that other factors may not be of equal or even
greater importance. Sommer and Hart (2) have shown that there
is no consistent relation between the titratable acidity and the heat
coagulating point of milk. This they found also to be true of the
hydrogen-ion concentration or true acidity of the fresh milk, but
they express the opinion that it may become a factor under com-
mercial conditions. They found, on the other hand, that the varia-
tions which occur normally in certain of the ash constituents have
an important part in determining the temperature at which it
coagulates.

The titration of milk in the usual way will give no indication of
the condition of the ash and may be very misleading as to the hydro-
gen-ion concentration.

The alcohol test has been used to a limited extent for determining
the quality of milk with special reference to its sanitary condition.

This test is usually made by mixing equal volumes of milk with 68 |

to 75 per cent alcohol and observing whether a coagulation results.
It is generally considered that a coagulation indicates bacterial
change in the milk, but Auzinger (3) shows that fresh milk not in-
frequently coagulates under these conditions and offers some evi-
dence to show that it is due to changes in the milk salts, particularly
in the calcium. Ayers and Johnson (4) show that while the alcohol
test becomes positive when an appreciable amount of acid or rennet
is produced in the milk there is no consistent relation between the
alcohol test and the total number of bacteria present.

They found that while the addition of acid phosphates to milk in-
creased the tendency to coagulate with alcohol, the neutral or dibasic
phosphate had the opposite effect. When dibasic phosphate is added
to milk considerably more acid is required to produce a positive
alcohol test than with the normal milk. .

While the work of Ayers and Johnson shows that the alcohol test
is not a reliable index of the sanitary quality of the milk, there is a
possibility that its action on milk may be correlated with the heat
coagulation point of the evaporated milk in such a way as to render
it of some value in grading milk in condenseries.

TEST METHODS USED.

The alcohol test as used in this investigation was made by mixing
equal parts of 75 per cent alcohol and milk and observing whether
coagulation takes place. In case the milk shows a visible coagulation

¥ Of del VGRESS

, ;

'

AAV @®A1AQ0Q07 i
MAY 261921 ;
'
:

OC Livin in Ts ZH {@:

ji

Ve

oe eae ae i one ee eee

ee er. ee ae

he Os

°

a —.
ew
sh S) DETERMINING QUALITY OF MILK FOR CONDENSERIES. 3

it is considered unsafe from the standpoint that the milk after
evaporation will not stand the heat necessary for sterilization with-
out becoming curdy. The test is practical and easy to make at the
weigh room. The test as used in this work was made by adding
1c. c. of milk to a small test tube containing 1 ¢. c. of alcohol and
mixing at once by inverting once or twice while holding a finger
over the top. Any reaction that takes place will be very quickly
evident, the large majority of tests showing coagulation immediately
or giving no reaction at all. The gradation of coagulation is shown
by the size of the curd particles formed. Unless the curd particles
formed are small the reaction is not at all difficult to distinguish,
even by one not familiar with the test. A mixture of milk and
alcohol giving “a negative reaction immediately breaks clear from
the walls of the test tube, while a mixture giving a coagulation
of fine particles will leave the walls of the test tube cloudy. Mix-
tures showing a medium or large particle curd formation are readily
discernible because of the adherence of the curd particles to the
walls of the test tube.

In the work of grading the milk at a condensery on a commercial
basis two small brass dippers of 2 c. c. capacity each were used.
Thirty test tubes arranged in a block of wood 3 inches wide, 2 inches
deep, and 18 inches long, having three rows of holes of the proper
diameter and depth, were first filled with 2 c. c. of the 75 per cent
alcohol by means of one of the brass dippers. Two men working
together then went through the individual cans, taking 2 ¢. ¢. of milk
from each and mixing it with the 2 c. c. of alcohol. No more time
was required than is necessary in making the acidity test.

The first work attempted with the alcohol test was to determine
whether any correlation existed between the coagulation and the
acid content of milk as measured by the usual titration method.
Samples of milk were taken from individual patrons at the weigh
room of the Grove City, Pa., creamery for the observations made.
Reactions with 75 per cent ethyl alcohol and titratable acidity were
determined shortly after taking samples and at stated intervals on
those not showing positive coagulation with alcohol, until such action
occurred. All samples which did not show coagulation with alcohol
at the outset were held in a water bath at 35° to 37° C. (95° to
98.6° F.) during subsequent observations. A tabulation of 211
samples of milk handled according to the method outlined shows
conclusively that there is no direct relation between the coagulation
of the milk with 75 per cent alcohol and the acid content of milk
as measured by the titration method.

4 BULLETIN 944, -U. S. DEPARTMENT OF AGRICULTURE.

EXPERIMENTS AT GROVE CITY CREAMERY.
COMPARISON OF ACIDITY AND ALCOHOL TESTS OF MILK FOR CONDENSING.

Finding no consistent relation between the coagulation of milk
by alcohol and its acidity content as shown by the titration method,

work was started to ascertain the relative value of the two tests. —

Samples of milk, representing all conditions met with at the con-
densery, were taken at the weigh room of the Grove City creamery. —

Five pounds of each sample selected—which in the large majority _

of cases represented a mixed milk of some particular patron’s herd—
was evaporated in a 10-liter flask under a vacuum of 25 to 27 inches ~
to a concentration of 21 to 1, the time required being from 50 to 70

minutes, with a temperature of 40° to 50° C. (104° to 122° F.). The

evaporated milk was placed in baby-size tins and sterilized in an
autoclave for 30-minute intervals at 121.1°, 112.8°, and 107.2° C.
(250°, 235°, and 225° F.). Portions of evaporated milk in 100 ¢. ¢.
Erlenmeyer flasks were run in the autoclave at the temperatures used
and also at 100° C. (212° F.) for 30 minutes to note the extent of
coagulation. When sterilization at 112.8° C. (235° F.) for 30
minutes indicated that the product would not stand a higher process-
ing, the next lower temperature was used, only two temperatures
higher than 100° C. (212° F.) being used. The cooled cans of steri-
lized milk were shaken for one minute before examination for gen-
eral physical appearance and curdiness.

The main observation of the sterilized samples of evaporated milk
concerned the extent of coagulation and whether or not they showed
curdiness after shaking. Curdiness of shaken samples was de-
termined by the physical appearance of the product and by mixing
a portion of it with hot water. In reporting on whether or not the
sterilized samples were curdy after shaking, the temperature of

112.8° C. (235° F.) for 30 minutes was used as a standard of compari- §

son. In the large majority of instances the curdiness was pronounced
enough to leave no doubt as to the accuracy of decision, and the
sample sterilized at the lower temperature quite generally substan-
tiated the classification given on the basis of the standard tempera-
ture used. On the other hand, the samples showing no curdiness
after sterilization were in most cases not at all difficult to classify, as
they showed, in general, less coagulation even with the higher
temperature.

Table 1 shows the results of sterilization of 90 samples of milk of
varying acidity, 45 of which coagulated with 75 per cent alcohol.
Forty-three of the 45 when evaporated and sterilized at 112.8° C.
(235° F.) for 30 minutes showed curdiness after shaking. Coagula-
tion of practically all these samples when evaporated was very pro-
nounced, in some instances being so hard that it was impossible in

DETERMINING QUALITY OF MILK FOR CONDENSERIES. 5

any manner to reduce the extreme lumpiness. Some of the samples
of low acidity showed as objectionable a curdiness as those of the
higher acidity, indicating the reliability of the alcohol test and un-
reliability of the acid test in picking out those which will not stand
the sterilization necessary in manufacturing evaporated milk.

The table shows also the result of sterilization upon 45 samples of
milk of varying acidity, all of which showed a negative reaction with
75 per cent alcohol. Forty-two of the 45 when evaporated and
sterilized showed no curdiness after shaking.

TABLE 1—Comparison of alcohol and acid tests at Grove City creamery. Milk
concentrated 21 to 1 and sterilized at 235° F. for 30 minutes. LHffect of sterili-
zation noted after shaking for 1 minute.

Coagulation with 75 per No coagulation with 75
cent alcohol. per cent alcohol.

ae Effect of steri- Effect of steri-
Acidity. lization. lization.
Hoteeieeces 19 Ge Potall
samples. = samples. .
ot ot
Curdy-| curdy. Curdy- | curdy.
Per cent.
0.14 to 0.15 3 3 (1 igi eh sei EG eet Matic a: a
eile:to 10 5 5 0 1 0 1
1Gito. 17 10 8 2 9 0 9
17 to .18 11 il 0 12 1 11
18 to .19 10 10 0 11 1 10
19 to .20 5 5 0 10 0 10
20 to .21 iS 1 0 2 1 1
| Total 45 43 2 45 3 42

It seems quite certain that there is some condition of raw milk
coagulating with 75 per cent alcohol, making it impossible to sterilize
without getting a curdy finished product, for such milks when evapo-
rated and sterilized give a much firmer coagulation than those show-
ing a negative reaction with 75 per cent alcohol. In some instances
the coagulation, even at the lower temperatures used, is such that the
product turns to a hard, cheesy mass incapable of improvement with
long-extended shaking. Figure 1, showing the type of curd ob-
tained in sterilization, indicates clearly the difference which must
exist in the condition of milk coagulated with 75 per cent alcohol.
Only 6.7 per cent of the samples made from milk coagulating with
alcohol gave a soft curd, the remainder giving either a firm or a hard
curd, both of which are as a rule difficult to shake out to give a
product showing no curdiness. With the evaporated samples from
raw milk not coagulating with 75 per cent alcohol 88.9 per cent gave
either a soft curd or no coagulation at all, the remaining 11.1 per
cent giving a firm curd. The soft curds shake out very easily, giv-
ing a smooth-bodied product of good consistency showing no curdi-
ness.

6 BULLETIN 944, U. S. DEPARTMENT OF AGRICULTURE.

The difference in the effect of sterilization upon evaporated milk
made from raw milk, showing negative or positive reaction with
75 per cent alcohol is further emphasized in figure 2, which shows
the curdiness found at all temperatures used.

To get complete figures on all the four temperatures it was as-
sumed in compiling these data that a sample showing curdiness at a.
temperature actually used would show curdiness at any higher tem-
perature. With raw milks showing negative reaction with 75 per

Raw milk curdlin Raw milk not curdtin
with 75% alcoho with 75% alcohol

Pi oococ ace

/,
FIRM CURP II-1 To

SOFT CURD

o:
iS
‘es

ves

x

$25

%

‘
os

ves

x

5

525
ves

ro

<>
j
<

‘es
e

‘es

*S
5

we

o,
o>
on

OOS" OOOO OY

Q
x

>

°,

?,
2,

:
8
52)
:
8

we nace
oe

RRR KK ROKK

RRR I :
weretaretorerecererereeleee OebsOre 010.0 s0cee,
SSeS SORES SCS SE SCR KG
950

"O° BreTey,
LL °,

WY

Tren Deere VAS

NO CURD
C6.7 7o

Y
MELEE

N

ROOF T CURD 672

Fic. 1—Types of curd obtained in sterilization of
evaporated milk.

cent alcohol only 4.4 per cent of the evaporated samples showed
curdiness at 100° C. (212°. F.) and 107.2° C. (225° F.) for 30
minutes; 6.6 per cent at 112.8° C. (235° F.) for 30 minutes; and
31.1 per cent at 121.1° C. (250° F.) for. 80 minutes. With raw
milks coagulating with 75 per cent alcohol, 57.7 per cent showed
curdiness at a temperature of 100° C. (212° F.) for 30 minutes, 80
per cent at 107.2° C. (225° F.) for 30 minutes, 95.5 per cent at 112.8°
C. (235° F.) for 30 minutes, and 100 per cent at 121.1° C. (250° F.)
for 30 minutes. These figures show quite strikingly a difference in

7
in-

hen

ness W

d

ing cur

Samples of raw milk

th alcohol and show

temperature necessary to
evaporated and sterilized can be sterilized without showing curdiness

1zing

]

1

a ster

oO
to}

in

10n Wl

diness when us

DETERMINING QUALITY OF MILK FOR CONDENSERIES.
sure a complete destruction of the bacteria.

g a coagulat

givin

it impossible to manufacture from it evaporated milk that will not
give cur

condition of milk coagulating with 75 per cent alcohol, which renders

IO. G@)% 676 Ooi WO: % . wv, “3: Fa
AKO q OO
55255 RRR RR Reo Meecececezere: S

etateraraeratata ly SRR RECO

OO

g3 ee ees

SES Beene meee see

=* ]M GG eS

=e W \
S
8

wyYy yyy

to

S yo

g3 WN WC Re e 22? \\\\\ .

70 per

eg from 60 to
cent of raw milks giving a negative alcohol test. This fact would

inin

ted milk sterilized at different temperatures,
ture conta

in a mix
d at every condensery some milk which

will not stand the required heat when evaporated by itself, but

%
%
Y
S
R
iS)

ss in evapora
1s receive

rdine

Undoubtedly there

Fic. 2.—Extent of cu
account for the variation in heat taken by different batches from day

to day.
which will go through all right when mixed with other milk. If the

of the finished product

8 BULLETIN 944, U. S. DEPARTMENT OF AGRICULTURE.

proportion of this milk is not too high no trouble will be experienced, —
but the proportion in some batches may be such as to cause consider=_
able trouble.
It is interesting to know that raw milk with a low titrate a
acidity and which coagulates with alcohol and shows curdiness after —
evaporating and sterilizing can be made to stand sterilization with —
no resulting curdiness by mixing with it the proper amount of milk
showing a high titratable acidity but no coagulation with alcohol.

RELATIVE VALUE OF ACID AND ALCOHOL TESTS.

The value of any practical test for determining the quality of milk
for condensing must depend largely upon its ability to determine —
whether or not that milk, when evaporated to the required density,
will withstand the necessary sterilizing temperature without becom-

ALCOHOL TEST Sa

SAMPLES + SAMPLES —
(09 8 7 6S 4°39 2 \ hie 3 45.67 6 eae

: ERE
BARRA SS
NT

No curd at 235°F for 3Omin.
Curd at 235°F. for 3OmI¢n.

¥ic. 3.—The relation of titratable acidity and the alcohol test to coagulation of the es
evaporated milk.

ing curdy. The flavor and odor are things which have to be deter-
mined by the senses of taste and smell. The tendency of milk with
objectionable flavor and odor to coagulate with alcohol indicates
additional value of the test from this standpoint, especially where —
little attention is given to these factors.

The preliminary work indicated clearly the unreliability of the ©
acid test, as ordinarily used in the condensery, for determining the ~
quality of milk for condensing. A comparison of the acid and
aleohol tests in determining what milk when evaporated would
stand sterilization without showing curdiness reveals the following:

Of 90 samples of raw milk taken at the-weigh room and repre-
senting a wide range of condition, 46 samples of the finished evapo-
rated milk showed curdiness after sterilization and shaking. Forty-
four of the evaporated-milk samples withstood sterilization, show-
ing no curdiness after shaking. Analysis of Table 2 and figure 3
shows that the alcohol test would have rejected 43 of the 46 samples

DETERMINING QUALITY OF MILK FOR CONDENSERIES. 9

at showed curdiness after sterilization and shaking, while it would
have rejected 2 out of 44 that were all right; that is, showed no
-curdiness. The acid test would have rejected 18 of the 46 samples
showing curdiness after sterilization and shaking, while it would
have rejected 21 of the 44 that showed no curdiness.
tal The following tabulation shows the percentage of satisfactory and
unsatisfactory milk samples that would have been retained or re-
_ jected by the alcohol and acidity tests: |
ey

Alcohol test. Acidity test.
(Per cent.) (Per cent.)

4 atisfactory MHC sAnples TeLAINGO a) eee eee 95. 5 Donte
fs

3 Satisfactory mum Samples rejectede: =! Stl" Len oe fae 4.5 4T.7
_ Unsatisfactory milk ‘samples’ retained{is 1 JAE ee 6.5 60. 9
- Unsatisfactory milk; samples rejected. 2+ iheG Sypris tyre 93.5 39.1

Table 2 gives a more concrete comparison of the relative value of
Eitis leehsl and acid tests in the work done at Grove City, Pa.

_ TaBLe 2.—Relative value of alcohol and chert tests on samples run at Grove

City, P.
|
Alcohol test. Acidity test.
Number
Kind of samples. of sam-
ples. Times Times Times Times
correct. |incorrect.| correct. | incorrect.
| Satiaetory oy tag Saeed IEE Se ed 5 See ee 44 4g 2 21 23
_, Unsatisfactory eer ae es ene Te ae OAL ES 46 43 3 18 28
na oe Ce nO eee Cee ee eee 90 85 5 ‘ 39 51
teem eee ee ches. it eecAd. 100 94.4 5.6 43.3 56.7

EXPERIMENTS AT CONDENSERIES.
WORK AT FACTORY A.

a Realizing the importance of trying out the alcohol test under other,
ineluding commercial, conditions, the work was extended to a con-
_ densery, which is designated as Factory A,? where considerable diffi-
culty had been experienced in making an evaporated milk meeting

_ the requirements of 26.15 per cent sata solids and 8 per cent fat.

The small laboratory apparatus used in the Grove City work was
Be set up in the laboratory of this plant and work of the same nature
as that done at Grove City carried on. Samples of individual pat-
~ rons’ milk showing positive or negative reaction with alcohol were
_ condensed to bring the product as nearly as possible to 18.15 per cent
solids not fat, uhins: being the portion of the evaporated milk causing
the difficulty in sterilization. It was the aim to have the énmmpliss
vt that were evapérated from raw milk showing no coagulation with
alcohol slightly above the point of 18.15 per cent solids not fat, and

_ 2 'The assistance of F. B. Evans in the work at this factory is acknowledged.

10 BULLETIN 944, U. S. DEPARTMENT OF AGRICULTURE.

low this point. Samples not showing close to this schedule are n
included in the discussion of results.

The samples of evaporated milk put up in baby-size cans were run
in a Berlin pilot sterilizer used by the plant in determining
amount of heat the different runs would stand.

The results of this work did not agree closely with those obtaineal d
at Grove City. All the samples of raw milk showing coagulation
with alcohol gave an evaporated milk that showed curdiness after
sterilization at a temperature of 112.8° C. (235° F.) for 30 minutes. —
As the samples of raw milk, showing no coagulation with alcoho 4
gave evaporated milks that in the majority of cases also showed —
curdiness, no real comparison could be made as to the relative me it
of the alcohol and acid tests. “

Table 3 shows the result of the work done at Factory A on indi- |
vidual patrons’ milk samples. Of the 22 samples of raw milk show- .
ing no reaction with alcohol, 14, after evaporating, showed curdiness —
at the standard sterilizing temperature used, which happened to be —
about what was found necessary to insure a sate keeping milk, while
8 showed no curdiness. Of the 12 samples of raw milk shay
coagulation with alcohol, all showed curdiness after they were evapo-
rated and subjected to the standard sterilizing temperatures.

TABLE 3.— Relation of alcohol test and titratable acidity in Factory A. Evapo-
rated milk having close to 18.15 per cent solids not fat. Hifect of sterilization — %
noted after shaking for 1 minute. e

a
q

Raw milk not coagulating] Raw milk coagulating
with 75 per cent alcohol. | with 75 per cent alcohol.
ae seh Effect of Effect of
Acidity. sterilization. sterilization.
Total Total
samples. ~! samples.
ot Not
Curdy.) curdy Curdy.| curdy.
Per cent.

Ohiltesr aia 20a |e en |S a ee | oe Be 1 1 0
.12 to’ '.13..5 4 2 2 0 0 0
Sto |.44..: 3 2 1 3 3 0

ela ttor Tonk 4 2 2 3 3 0
IDS rfayp va Use 3 3 0 4 4 0
16itO "LT D 4 1 0 0 0
I7to, 218 3 1 2 1 1 0
DSito MLR EL EeER ee | BERR RI 0 0 0
Total....- 22 14 8 12 12 0 .

The alcohol test was further tried out on a commercial basis in
this plant. The individual cans of milk received at the intake q
were tested with alcohol according to the method already described. — o
All the milk showing no cham aleei bn with alcohol was run in a sepa-— r§

rate vat and condensed in the large factory pan as a separate batch. —

DETERMINING QUALITY OF MILK FOR CONDENSERIES. 11

_ A composite sample of the milks showing coagulation with alcohol,
along with a sample of that showing no coagulation, was run in
_ the laboratory apparatus as a means of comparison. Out of 4 trials
the raw milk showing coagulation with alcohol gave an evaporated
milk that in all 4 cases showed curdiness after sterilization at the
standard temperature, while the evaporated milk from the raw
milks showing no coagulation with alcohol showed curdiness in 3
out of 4 cases. The 4 batches of milk, the individual cans of which
showed no coagulation with alcohol and which were run in the
; large factory pan, all showed curdiness after sterilization. Several
laboratory runs made on milk taken from the large receiving vat
_ at different times, to get representative samples of the milk received,
_ failed in all instances to give an evaporated milk ‘that would meet
the required standard and not show curdiness after sterilizing and
’ peeing.

_ The general failure of milk, accepted on the acid test at this con-
ts to withstand the necessary heat after being evaporated,
suggested that it might be due to a deficiency in the composition
-and balance of milk Ecsite. as reported by Sommer and Hart (2).
The fact that the aalaktiern of a small amount of dibasic potassium
phosphate, which is a normal constituent of milk, corrected the
excessive tendency of the milk to curdle in sterilization indicates
_ that this assumption was correct.
_ Consideration of the manner in which milk at this plant was
handled, in connection with the results obtained, indicates that the
; Bicaditions were quite different from those that the average con-
-densery has to contend with, and for this reason it appeared F iehia
_ desirable to try out the alcohol test at another place.

WORK AT FACTORY B.

. “The work was then continued in a condensery, designated Factory
3 B, located in a region where dairying forms a minor part of the
4 fattn operations. TAS a result of this condition the milk received
_ was not of good quality. All the work done at this plant was on a
- commercial basis, the milk being graded at the intake and run into
_ separate tanks according to its reaction with alcohol. Separate runs
of the milk showing, respectively, coagulation and no coagulation
' with alcohol, were made in the factory pans, and after retaining the
_ required amount of each batch of evaporated product for the experi-
mental work, they were mixed in one tank and handled in the usual
Manner by the factory. Because of the small proportion of milk
- received that showed coagulation with alcohol, the batches from this
kind of milk were smaller and in some cases it was necessary to hold
them over until the next day in order to get enough for a run in the

to a very iow temperature and held in that condition overnight

only a very slight increase in acidity was shown.
The eduporated milk from each run was standardized to choi

close to 18. 15 oe cent solids not fat. The samples, from the sabi

slightly above this figure. All samples were sterilized in one of 0
large Fort Wayne sterilizers used regularly by the condensery.

were made in this factory. The evaporated milk from the raw milks
showing no coagulation with alcohol in all cases came through the —
sterilization process in fine shape, producing no curdiness and indi- —
cating that they would have stood more heat; in all four cases, also,
the evaporated milk from raw milks showing coagulation with
alcohol gave a pronounced curdiness that could not be removed by
piolonnbel shaking.

TABLE 4.—Results obtained by grading with the alcohol test at Factory B., fa

|
Raw milk. Sclids ae
Reaction| not fat ee
nak Acidity. ie Ble in ayer evaporat-
No. | Weight. ae sulk. | ed milk.
Pounds. | Per cent. Per ceni.
Lovee 12,400 0.140 — 17.96 | No curd.
Dns 4, 250 .170 + 17.06 | Curdy.
Seeks | 10,100 . 150 — 18.53 | No curd.
ee 9,100 SLt5 + 18.16 | Curdy.
Oe See 11,500 - 165 — 18.24 | No curd.
eaeae 9,100 .175 “ 18.16 | Curdy.
hanes 12,400 . 145 — 18.25 | No curd.
Shite 6,300 . 160 + 17.91 | Curdy.

Table 4 gives the data on the four trials of grading and condens- —
ing at this establishment. The titratable acidity of the lots of milk ~
showing coagulation with alcohol is somewhat higher than that of the |
milk ae no coagulation with alcohol. We have no definite
data that pall enable us to say this difference in acidity would ac-—
count for the difference in coagulation. In order to throw some
light on this question, four cans of the sterilized milk were sent to a
the Jaboratory where the hydrogen-ion concentration or true acid 7
was determined with the following results :3

Lot, pH.
Bir ae eae eee de as Sat a ES
Oj ee IS eae EE A Sera Gare 8 5.80
Tip ett ck sc aR 6 ae alk Be AR 5.90

Myf UATE) Ae Bek SEOUL STAC 5.84

*The determinations weré made by H. F. Zoller, of the Dairy Division.

DETERMINING QUALITY OF MILK FOR CONDENSERIES. 13

a _ While in each case the real acidity of the lot coagulating with
alcohol and curdling in sterilization is higher, the difference is so
small that it is very doubtful if it would more than counteract the

CONCLUSIONS.

1. The acid test as ordinarily used will reject a portion of the un-

_ satisfactory milks, but as a whole it is unreliable and inadequate as

a means of determining the quality of milk for condenseries where

_ evaporated milk is manufactured.

_ 9. There is no direct relation between the coagulation of milk

_ with alcohol and its titratable acidity, but milks high in titratable

acidity as a result of fermentation will in the large majority of cases

_ show coagulation with alcohol.

8. The alcohol test shows good possibilities as a practical and

reliable test for determining the quality of milk for condenseries

_ making evaporated milk. How generally the test can be applied will

require further investigation at other condenseries. It is believed

that it can be used to advantage in a large majority of average
factories.

; LIST OF REFERENCES.

- (1) Rice, Franx E.

1919. Milk with high apparent acidity. Jn Science, N. S., v. 50, no.

1296, p. 424.

_ (2) Sommer, H. H., and Hart, E. B.

2 1919. The heat coagulation of milk. Jn Jour. Biol. Chem., v. 40, no. 1,

a p. 137-151.

(8) AUzINGER, AUGUST.

. 1909. Studien tiber die Alkoholprobe der Milch, ihre Verwendbarkeit
zum Nachweis abnormer Milchen und ihre Beziehungen zu anderen
Priifungsmethoden pathologischer Milch. In Milehw. Zentbl., v. 5,

no. 7, p. 293-315; no. 8, p. 352-370; no. 9, p. 393-418; no. 10, p. 430-446.

(4) Ayers, S. Henry, and JoHNsSON, WILLIAM T., JR.

1915. The alcohol test in relation to milk. U. S. Dept. Agr., Bul.
no. 202.

O

a

LIBRARY 0

0

ONGRES: