A NEW METHOD OF GRADING

MiLK AND CREAM,

By Wm.C,Woodward,

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UNITED STATES PUBLIC HEALTH SERVICE

A NEW METHOD OF GRADING
MILK AND CREAM

BY
WM. C. WOODWARD
Health Officer, District of Columbia

REPRINT No. 117
FROM

PUBLIC HEALTH REPORTS

FEBRUARY 21 1913 |

WASHINGTON
GOVERNMENT PRINTING OFFICE
1913

SS 5S |

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A NEW METHOD OF GRADING MILK AND CREAM.'
By Wm. C. WoopwakRD, Health Officer, District of-Columbia.

That the score card has been of service in the improvement of
sanitary conditions on dairy farms, possibly few will deny. It has
failed, however, with respect to one most important feature of milk
control inasmuch as it does not afford a sufficient basis upon which
to found an opinion as to the wholesomeness and nutritive value
of milk as it reaches the consumer. And if the scores of dairy farms
give but an imperfect idea of the quality of the milk as it reaches
the consumer, an attempted study of a series of scores of dairy farms
and milk shops, chemical analyses and bacteriological analyses leaves
the inquirer who is not technically skilled with respect to the matter
in a dazed and quite helpless condition. In order to enable the
consumer to determine the. quality of the milk he is purchasing, the
health department of the District of Columbia has devised a method
for grading the finished product.

Essentials of the grading of milk.—Any ideal system of grading
milk as delivered to the consumer must take into consideration
the condition of all of the farms from which milk is or is liable to be
derived, the condition of the milk shop from which it is distributed,
the chemical analysis of the milk, and the bacteriological analysis.
The result must be expressed in a manner easily understood by the
public and in a way that will afford ready and fair comparison between
milk from any number of sources.

Method of grading.—The method of grading milk adopted by the
health department of the District of Columbia is as follows: 100 points
are allowed for the dairy farm, both equipment and management; 100
points are allowed for the cattle; 100 points are allowed for the milk-
distributing station, if the milk is not distributed directly from the
farm; 100 points are allowed for the chemical analysis; and 200 points
are allowed for the bacteriological examination. The total number
of possible points is 600 if there be a milk-distributing station, and 500
if there be no such station. By dividing the total number of points
allowed by the total number of points possible a figure is obtained in
the form of a decimal fraction representing the grade of the milk.
Any unusual conditions bearing upon the nutritive quality of the
milk or on its wholesomeness, but not susceptible of being reduced to a

1 Reprint from the Public Health Reports, Vol. X XVIII, No. 8, February 21, 1913.
80926°—13 (3)

i

percentage basis, are to be set forth in an explanatory note, if the grade
is computed during the continuance of such conditions; such, for
instance, as a milk-borne outbreak of typhoid fever or other conta-
gious disease.

Rating the cattle—For a number of years past the health depart-
ment of the District of Columbia has scored health and cleanliness of
cattle independently of the general score for management and equip-
ment of the dairy farm, allowing 100 points for each. It has seemed
to the department that under the method of scoring ordinarily
adopted, enough weight is not allowed for the health of cattle nor
enough latitude for variations in their healthfulness and cleanliness.
But while the system of scoring cattle independently of farm manage-
ment and equipment facilitates the scoring of milk in the manner
herein described, yet with a simple mathematical adjustment the
method can be used anywhere.

When the milk distributed through a given establishment comes
from but one farm, the determination of the rating to be assigned to
the cattle is a simple matter, requiring merely the finding of the aver-
age of the scores given the cattle at a series of inspections by the
dairy-farm inspectors. But in every large milk-distributing estab-
lishment the milk comes from many farms, and these farms vary
widely in the number and condition of the cattle maintained for
dairy purposes. The milk distributed from such an establishment
is a composite of the milk from all of the contributing farms. The
influence of each farm on the composite mixture, however, is not
equal, but depends upon the proportion and quality of the milk it
contributes as compared with the whole output. For practical pur-
poses the proportion of milk supplied may be regarded as deter-
mined by the number of cows maintained. The method adopted,
therefore, allows weight to the score for each dairy herd proportion-
ate to the number of cattle it contains. The score for the herd on
each farm is multiplied by the number of cattle in it. The total
number of cattle in all contributing herds is learned by reference to
the dairy-farm records. Then all of the scores, multiplied as above
described, are added, and the sum thus obtained is divided by the
total number of cattle. The quotient is the rating for the cattle.

The method may best be understood by a simple illustration.:
Producers A, B, and C all send their milk to Dairy No. 342. A has
100 cows, scored 100. B has 50 cows, scored 80. C has 10.cows,
scored 40. To determine the rating to be allowed for the cattle in
computing the final score:

Producer.

Neo ies tla ee eee eee (number of cattle) 100 (multiplied by score) 100=10, 000
Bic: Epa e Bae (number of cattle) 50 (multiplied by score) 80= 4,000
C: 2.7. eee eee ee naa (number of cattle) 10 (multiplied by score) 40= 400

160 14, 400

5)

Dividing the sum of the multiplied score, 14,400, by the total number
of cattle, 160, the quotient is 90, the rating to be allowed for the cattle
in determining the grade of milk distributed by the common
distributing agency, Dairy No. 342.

The significance of the method is best understood by supposing
that the 100 cows on the farm of A were scored 40 instead of 100 and
the 10 cows on the farm of C were scored 100 instead of 40, the score
for B’s herd remaining the same. The resulting rating would then
be as follows, notwithstanding the fact that the milk would still come
from exactly the same number of cows, on the same farms, with the
same ratings, viz, 40, 80, and 100.

Producer.

rs (number of cattle) 100 (multiplied by score) 40=4, 000
ae bX pie she ieee (number of cattle) 50 (multiplied by score) 80=4, 000
Dera wade a's «Veh c nae (number of cattle) 10 (multiplied by score) 100=1, 000

160 9, 000

Dividing the sum of the multiplied scores, 9,000, by the total number
of cattle, 160, the quotient is 56.25, the rating for the cattle in
determining the grade of the composite milk output.

If the simple method of averaging the scores of all herds without
reference to the number of cattle in each had been adopted, the rating
would have been the same tn each instance: (Score 100, plus score 80,
plus score 40) divided by the number of herds, 3, equals 73.33.

The method of rating the cattle has been described at some length
and enlarged upon by illustrations in order that it may be made per-
fectly clear. The elaboration may possibly have served to convey the
impression that the method is complicated, but a few minutes’ study
of it will show that such is not the case. The application of the
method to any considerable number of dairy-herd ratings will, how-
ever, certainly be tedious unless the records have been kept especially
for the purpose of facilitating such computations. This department
has devised a system of record keeping, illustrated in the table on
page , that is expected to facilitate the making of such computa-
tions in the future. In the meantime, in determining the rating of
the cattle furnishing milk to any particular distributing establishment,
the department will not undertake to consider the score .for every
dairy farm but only for a number representing a fair average, say five,
selected at random.

If on any farm a substantially new herd is obtained, as when a herd
is tuberculin-tested and all ‘‘reactors” are eliminated from it, the
rating for dairy cattle is based solely on scores for the new or reno-
vated herd.

Rating of the dairy farm.—What has been said with reference to
the determination of the rating -to be assigned to the cattle applies
with equal force to the determination of the rating for the equipment

6

and management of the dairy farm. Due weight must be allowed
for the amount of milk that each farm supplies, and this can be done
in the same way as weight is allowed for the score for health and
cleanliness of cattle, pointed out in the preceding paragraphs.

Rating of dairies—The term “dairy” in the District of Columbia
is regarded as meaning merely the place from which the milk 1s dis-
tributed within the city. As every establishment is scored on the
basis of 100, it is necessary merely to take a number of scores of
the dairy under consideration sufficient to be fairly representative,
say three, and to find the average.

Rating of chemical analyses.—The value of the chemical analysis of
milk lies in the fact that it shows the food value. Cases of deliberate
watering are in this jurisdiction rare, and the use of preservatives and
coloring matter is practically unknown. In order that the results of
chemical analyses may be used in the grading of the milk, it is neces-
sary to reduce them to a scale, with 100 as a maximum. As the
nutritive value of milk is determined by the total solids, the scale
adopted by the health department is based upon the percentage of
total solids and not upon the fat. The scale is as follows:

Scheme for rating chemical analyses.

Total solids: Rating.
Ligper cengpr dead. a. wena. = 2 lesen Sa rs eben ie se ete ded bee ee ee 0
More than 11 per cent but not more than 12 per cent................------ 40
More than 12 per cent but not more than 12.50 per cent........-...------ 60
More than 12.50 per cent but not more than 12.75 per cent..........------ 70
More than 12.75 per cent but not more than 13 per cent.............--.-- 80
More, than 13 per cent but not more than 13.25 per cent..............-.-- 90
More than 12.95. per Cems. ..k, cas ivecs ces ne nen aapiey pe ee ee 100

If any sample contains added water, deduct 40 points. For milk
containing preservatives of any sort deduct the entire chemical
rating, and give zero for the bacteriological rating immediately
preceding the finding of the preservatives. The average rating of not
less than three consecutive analyses is to be taken.

Rating of bacteriological analysis —In determining the grade of
the milk as sold, 200 points are allowed for bacteriological analysis.
As some bacteria are found in all milk in the ordinary channels of
trade and may, therefore, be looked upon as commercially normal,
the primary rating takes into consideration merely the total bacterial
count. Bacilli of the colon group and streptococci are, however,
looked upon as foreign to wholesome milk, and for their presence
certain deductions are made from the rating allowed on the basis of
the total bacterial count alone. The remainder represents the
absolute rating for the bacteriological examination of the milk.
The standards adopted are as follows:

if

Rating for bacteriological findings.
: ; - Points
Raw milk. Pasteurized milk. bowed:
PSETIMET Si SV a ee ee 100,000 and upward......... 0
eel UCU os LIES ee ee ee 90,000 to 100,000. .....-.-.-..-| 20
duc Ly iN eP CORPO Te ta ee BE AES at a ae a 80/000 to 900002. ee see 40
2n EPO TG SE ETT TE See ee eee ae 70,000 to 80,000.............- 60
UTD TD NC Se Bap 9 ee a 60,000 to 70,000. ......--.--.- 80
TNE PLONE MMMM MES et anche c inne oes co tiln itu pwns Ss wlcnee cleo cine 50,000 to 60,000.............- 100
EMU UL MAD SUGUH 1 2 7 obi Se hg Seen aS SPs 2S ed 40: N00 tO: 500002. = asec: ees 120
PLUG EDULE Ts Sa SE ees a ae ee See 35,000 to 40,000. -.....----... 140
PUNT MD ERI tee te yatn ye alas aelnw eines we = oie cisiwiswie die ec wiennp ode ease 30;000!te 35,0005 52.2.2 ..se.-2 160
UEPEEDED C2 SUT She Segue SRN Sie ee See oe eee eee 25,000 to 30,000. ............. 170
POU MMPMED NTE MNILS 0 oor Smidaei se epee oe ase - wena te ioe oS ao wae a | 20,000 to 25,000......----..-- 180
Pear Mee rege ci erceiscie eae ole mae ole eee uh oncin wc p <inien 2 -| LO,DOOTO AOU: ..c. .o2.- ec a 190
WAT PEG Ua eta eS (HO M0R te 152000. cis... s% - 195
J aSSt TSU CTO Se ee ee ne eee ee ee Less than 10,000. .....-.-...- 200
For the first 1,000 colonies of the colon group or streptococci, For the first 100 colonies
whichever may be the more numerous, deduct 20 points and | of the colon group or strep-
deduct 10 points for each subsequent 1,000. tococci, whichever may be
the more numerous, deduct
10 points, and deduct 2
ve for each subsequent
100.

It will be noted that the foregoing plan for the evaluation of the
bacteriological findings lays down a basis for raw milk different from
that for pasteurized milk. This is undoubtedly fair when the ratings
of two or more samples of milk of the same class are to be compared,
but it would be manifestly unjust to compare such a rating of raw milk
with a rating of pasteurized milk unless this difference were taken
into consideration. In order to prevent such unfair comparisons,
ratings for pasteurized milk should be accompanied always by some
descriptive term, say the word ‘‘pasteurized,” and if it be desired
to compare the ratings of pasteurized milk with a rating of raw
milk, both should be scored on the same basis, preferably that for
raw milk.

Hypothetical cases may easily be conceived in which the scales
laid down above would give figures manifestly misleading, and
possibly such cases may be found in practice. Such would be a
case In which the colonies of the colon group or the streptococci
were numerous while the general bacterial count was very low. A
fair.examination of a reasonable number of entries in the records of
this department, however, failed to reveal any instances of this kind.

In any case the average rating of not less than three consecutive
analyses is to be taken.

8

Examples. —As an illustration of the way in which the method of
scoring described above works out in practice, the following —
are given from the records of this department:

Health Department of the District of Columbia—Dairy record. .

DAIRY NO.1. LICENSEE: JOHN DOE. RAW MILK.

Dairy farm. ae Bacteriological analysis.
_| 31 3 [Dairy] 2 + 3 Remarks.
pee. os | 3 | 8] & |score. = g 3
2/3 |2)| 32 2 ob 3 .| 3 {|
g niet eee | A & gla} s
a | s/3| 8 Se fet) ao he
Fx A Ve) cm H aa] Et” 9 | ia
1912
ADT PLS. tease CML shes ee [eee ae ec an fasese se 13:32) LOO Ss Sane cleans eee eee
BV 292 Spar. Sacer eres 934: ZOOM OO) 9953" sacs oI. come cl seeece| om cian «oem sl Coe eee
OCthO Ss. sesh eaten | ees Sere ee eee cleenecc 86:61)... 225, | 2eeeceleeese~ «sea bes oReieg aaa
ENO Waid eis laiciae x ttt a (ota aieicl| Shee eaall eaten ail wee 84.68) | <2. 20-]22 5-5 2l ees -|) 5 85 eee eee
INDY ped lc Coco ens seks somes aR ec el eee el taser dindecese|eanaste 2,100 0 0} 200
Lh Seer acer Oreee 934 | 160 | 100 | 98.0 |...-.--- See Sor Benes Sess se ress (scr Se <
Ls ip aan eee ee Bae Aor | Sire ayant? eae eee eee 5,000| 0} 0| 200
1913.
Jan. AO. 6 aac aon corte os 934 ||.150)) JO0;) 98:55) 5.50 <dlee ese |eeeee ol eel tee spe lea ei
PB epL aoe c tamctoc es See ce ais tee teat see] seem BO022 Sse sac-| 22 senna eee cosas need eee
are Ae ee ok te Sees eke cigs aa he eI Meters alee ys once 13.54 )| 100) eo 52..4e-4 52 oa2| ee en eee
WAM esse tee eiie ad ie atic oleaecutcs cee | pone ceacmee 13.32 LOO" | Soe ciatern lass scl ee cee | amore
PEC, 5 eine « cpt |<ientatl a eae ee onl ad te laeaadsulae-Pee 2,800| 0] 0| 200
Ratings for milk Feb.10.|......|..... 100) | .98:6.)|, 85,2) |o<2.3-- 100 A exeScee| coe lates 200

Grade for output of Dairy No. 1, John Doe, proprietor, 97.3.
Note.—This is the grading for a special milk, sold for more than twice as much as ordinary market milk. y
DAIRY NO.2. LICENSEE: RICHARD ROE. PASTEURIZED MILK.

1912,
WaTyple = deccameme S2 W327 (G3) RO ROSA eae sentence Bocca annie nace com ae eee
Bept. 19 3522..et teens ol 764. |. 740") (100 9 Bara); Seb 5 4S Ie eee, Sak Sa SS eee eee
CEA Sse Cees ted nses oe serlict sca] coco eles sone 99) 85 Te 25 Sool Seo ee peace inl cea tals cee? eee
IN (ay Al Se ne eee «|e Be eS ere | ns 99637 <i26o5cSls6 daa aloe me dee tae se coed 2 eee
INOVat ese secon caa tent. 2. al com eeieeocalnceesalsec nae 13; 3201-300 os aeeee ese epee eee eee
INOVe lat: Serene SEA ee an 3 AoA ee ee bere ks SPE Ee 13.08 90:15... eS ee ee
BOS Ba ciis «eet Seas oe 4945 1D ATO G82Oe) is sed = ec eae alee ae 2 See nee eens
DECS24: Se Ae aes 383 21 BFA GONGS"| eS a ate Bohs ote least s.< clekne ef aaron eee ene
1913. {
TANG ete cide ice tomttecel Pe coal sce’ co] ose5 sectee les omens aeemee sl ceseak 21,000 | 200 | 100 | 168
ERT ual SMES LF ee NE SSA oR 8 8 RES eee RE SS eee ar eee 5 Se fap 2 5,000 0 0} 200
DRL RES ane ras ey (ee ae Sears | Pea DOTS leno Seed sek Sal eer a eS ees
Jem 19 Si ee eee eee. ele te onc oases. cee oat asl see tet mebeee | eo cee 3,000 0 0| 200
vs pd a ee eee C034 29H GG ATTA eo a ocle se es oc seee ame ceee aati aan eee
ADT OO eee eee te wh ge reel aes ase smc ete ees 13.17 Ll ee eee ee ee ee
Ratings for milk Feb.10. / seat bees d 75.4 | 66.4 | 99.7 |....... O3.3)|C Sec als eee] eee 189.3

Grade for pasteurized milk sold by Dairy No. 2, Richard Roe, proprietor, 85

Rating of cream.—While no chemical or bacteriological standards
have been laid down for cream and other milk products, the method
of grading described above may readily be applied to them, proper
scales being first established for chemical and bacteriological data.

Conclusions.—The method of determining the nutritive value of
milk and its wholesomeness and of expressing them in a single figure,
as described in this article, is not perfect or final; it will be improved

9

as the result of the future experience of the writer and of others. It
is believed, however, to mark an advance in the supervision and
control of the milk supply in that it enables the supervising officer to
give to any consumer definite and easily understandable information
as to the relative nutritive value and wholesomeness of milk from
different sources in the very form in which the milk from each may
be expected to reach the consumer. The method is applicable to
any grade of milk, from certified milk to “cooking” milk, and prices
may be fixed according to the grade of the milk furnished, without
any formal “certification” as the term is now understood, and with-
out any official “classification.”

As the method of scormg herein proposed becomes familiar to the
consuming public, of all milk selling at a given price that milk will
be most in demand which has the highest rating, and if circumstances
make it expedient to increase the price of milk, a dealer, if his milk has
a high grade, can logically refer to that fact in justification of the
increase. To every dealer who desires to increase his business and
to every dealer who wants to raise his price—and this would seem to
include all dealers whatsoever—a high grading of his output becomes
of commercial value. Clearly, however, in order to obtain a high
grading for his milk as he delivers it to the consumer the dealer will
not only have to see that the milk is carefully handled after it comes
‘into his possession, but will have to obtain it in the first instance from
farms that score high. The dealer, therefore, will have to keep in
closer touch than heretofore with farms that produce milk for him.
A good farm score becomes then also of commercial value, since such
a score sustains the grade of the milk as delivered, while a low farm
score pulls it down; and it becomes of more interest to the farmer
than it now is to conduct his farm in such a manner as to obtain the
highest score possible. ,

The method of grading milk herein proposed reduces to a minimum
the influence of the personal equation. The scoring of a single farm
by the same dairy farm inspector at different times or, as will most
commonly be the case, the scoring of different farms by different
inspectors at different times, and the scoring of the dairy or milk
shop at still different times and by other inspectors, will reduce the
personal equation very much; and with respect to all, except pos-
sibly the very last score, that will be taken into consideration when
any given milk grade is computed, the interested farmer or milk
dealer will have opportunity to appeal from the inspector to the
higher supervising officer before the score enters into the grading.
Chemical analyses will, moreover, presumably be made by one person
and bacteriological examinations by another, and as three or more of
each of these will enter into the final grading, it may be possible
even that two or more chemists and two or more bacteriologists will

10

participate in the work. Certainly, then, personality can have but
a minimum influence in determining the final grade—that is, if we
except the influence of the personality of the milk producer and the
milk dealer in each conducting his business as it should be conducted.

As the records of the department have not been arranged with a
view to the grading of muk in the manner proposed in this article, the
computing of milk grades will for a time be troublesome. The ~
rearrangement of the system of record keeping in such a manner as
to facilitate in the future the computation of milk grades will involve, .
however, no great difficulty. A tentative arrangement is shown in
the specimen gradings which appear on page 338, figures from actual
records having been transferred to the form of record which it 1s
proposed to keep. Figures are to be entered on such a proposed
record daily as they come in from the inspectors and from’the labora-
tories, but it will be necessary to compute ratings for the milk only
when request is made, or otherwise at stated intervals, say monthly,
or quarterly. The results of such periodical computations should be
communicated to the milk dealer primarily interested, for his infor-
mation and guidance, and such a course will be followed if clerical
assistance be available for that purpose.

While the grading of milk in the manner decicfaianei in this article
will consume some time and, therefore, add to the cost of the milk
inspection service, it will make of practical value many reports and
figures now collected at a considerable cost, and then buried in the
official records without affording a basis for intelligent action by the
milk supervising authority or, what is even more important, for
intelligent action by the consuming public, which, after all, is in
supreme control of the milk situation.

: O

GAYLORD BROS.

MAKERS

SYRACUSE,

PAT. JAN, 2!

viv

0000895