UC-NRLF

ROSS

UNIVERSITY OF CALIFORNIA LIBRARY

LABORATORY GUIDE

IN

MARKET MILK

BY

H. E. ROSS,

Professor of Dairy Industry, New York State College of Agriculture
at Cornell University

1915

CARPENTER & CO.
ITHACA. N. Y.

COPYRIGHT
1915

CARPENTER & Co.

PRESS OF W. F. HUMPHREY, GENEVA, N. Y.

PREFACE

The production and handling of clean milk is based on scientific
principles. It is true that many of these principles are simple in their
application and oftentimes on account of their simplicity they are
overlooked and neglected. It is the purpose of this laboratory guide
to enable the student to better understand the application of science
to clean milk production, and to impress on his mind the necessity for
attention to detail in this branch of Dairy Industry.

Our ideas concerning the best methods of clean milk production
are constantly changing. The Author recognizes that this will
necessitate frequent revision of this book and an effort will be made to
keep this laboratory guide thoroughly up-to-date.

H. E. Ross.

Dairy Laboratories

New York State College of Agriculture .
at Cornell University
Sept. 14, 1915

It is generally accepted that clean milk means milk which is free
from microorganisms or the products of their action. It is possible
to conceive of milk being impure from something other than micro-
organisms or their products, such as the addition of some poisonous
substance to milk. The possibility of such contamination is, however,
so rare and so remote that the words "impure milk," have come to
mean that which is affected by the action of microorganisms.

For this reason all operations and experiments performed in a
laboratory should be done in such a way as to prevent bacterial con-
tamination, and all dairy utensils with which the milk comes in con-
tact should be rendered sterile so far as possible. This can be done
by thoroughly scalding all dairy apparatus, or better still by
exposing them to live steam for not less than one hour. If the
dairy utensils are scalded by means of hot water, the temperature of
the water should be not less than i8o°F. and it should be as near the
boiling point as possible.

Dippers and other dairy utensils in which milk is handled, or which
comes in contact with the milk in any way, should not be laid on the
floor and then placed in the milk. Care should be taken not to touch
the surfaces of dairy utensils, such as coolers, bottle fillers and so
forth, with the hands. Water even in small amounts, may, if allowed
to enter milk, cause it to putrefy.

CLEANING DAIRY UTENSILS

Dairy utensils must be thoroughly cleaned if milk is to be handled
in a sanitary manner. The proper way in which to clean a dairy
utensil is to first rinse it with cold or luke-warm water, preferably the
latter. This removes most of the milk from the utensil and prevents
later cooking of the albumen of the milk on to the apparatus, when it
is scalded or sterilized. The utensil should next be thoroughly washed
by means of a brush and hot water in which there has been dissolved
some good washing powder. An excessive amount of powder is not
necessary, a tablespoonful to a pail of hot water is usually sufficient.
The utensil should then be scalded in hot water, and if possible,
exposed to the action of live steam for not less than one hour, thereby
rendering the utensil as sterile as possible. It should be kept in a
place where it will not become recontaminated.

EXPLANATION OF EXERCISE I

In studying any dairy utensil, it should be noted whether the uten-
sil is so arranged and constructed as to best fulfill the purpose for
which it is intended. All dairy utensils should be as simple as possible
in construction. They should have no seams and crevices into
which milk can collect. Any cracks or seams in copper or tin
surfaces should be well flushed with solder. All parts should be
accessible so that they may be thoroughly cleaned. They should
be strong and durable and at the same time, any extra metal or other
material is objectionable. On account of its durability and the ease
with which it may be cleaned, metallic is usually preferable to wooden
construction.

When possible, metallic construction should be of some non-rusta-
ble material.

EXERCISE I
A STUDY OF DAIRY APPARATUS

1. Bottle Fillers — Study the tubes of the different fillers used.
Show by drawings how the milk flows from the tank through the tube
into the bottle, and the provision made for removing air and surplus
milk from the bottle.

Pasteurizers — Show by cross-sectional drawing the method of
operation of a holder pasteurizer and a flash pasteurizer.

2. Clarifiers — Explain the action of a centrifugal clarifier. In
each case show by means of a drawing the chief differences between
the inner device of the clarifier and a cream separator of the same
make. Also compare the relative speed of clarifiers and separators
of the same make and having the same capacity per hour.

3. Coolers — Make drawings of a conical and tubular type of
cooler and explain the action of each.

In case of the tubular cooler, show its connection with a brine
barrel and indicate the relative position of the cooler, brine barrel and
pump.

4. Milk Bottles — Make drawings of two different styles of milk
bottles.

DIRECTIONS FOR STANDARDIZATION

The process of standardization consists in raising or lowering the
percentage of fat in milk or cream to a definite standard. This is
done by adding milk of a higher or lower fat content, than the material
which is being standardized.

Some market milk does not normally contain sufficient fat to be
satisfactory to the consumer. In order to make this milk satisfactory
the dealer oftentimes standardizes it by the addition of cream.

Since the law states that unadulterated milk is milk to which
nothing has been added or anything taken away, there has been
raised some slight question as to the legality of the process of stand-
ardization. However, the addition of cream to milk increases its
value, so that no serious objection has been raised to that part of the
process. One would, however, have no right to reduce the fat con-
tent of milk by the addition of skimmed milk, as this would be
essentially the same as removing fat from the milk.

At the present time much of the cream sold is paid for on a basis
of its fat content and for this reason a knowledge of standardization is
useful to the cream shipper. If a dealer receives a certain price for
cream containing a definite percentage of fat it is desirable to have no
more or no less fat than the percentage agreed upon. If there is more
fat than the contract calls for, the seller loses, and if there is less fat
the buyer loses.

In standardization there are two classes of problems involved:
first, one in which two products containing a known percentage of fat
are mixed to make a definite amount of milk or cream containing a
fixed percentage of fat, and second, one in which a definite amount of
milk or cream of a known percentage of fat is used and enough of some
other product added to make the resulting mixture test the desired
percentage of fat. In the first case the amount is definite, and in the
second case it is indefinite.

The usual method of working standardization problems is quite
difficult, but Pearson has devised a method which greatly simplifies
the computation. It is as follows: Draw a rectangle and place in
the center of it the percentage of fat desired. On the left hand
corners place the percentages of fat in the materials to be mixed. It
is customary to place the larger percentage on the upper left hand
corner and the smaller percentage on the lower left hand corner,

8

although the position of these numbers might be reversed without
affecting the results. Subtract the smaller number on the left hand
corner of the rectangle from the number in the center and place the
remainder on the diagonally opposite right hand corner. Then sub-
tract the number in the center of the rectangle from the larger number
on the left hand corner and place the remainder on the diagonally
opposite right hand corner. The two numbers on the right hand
corners of the rectangle represent the number of pounds of materials
required. The sum of these two numbers will be a mixture containing
the desired percentage of fat, expressed by the number in the center
of the rectangle.

In each case the number on the right hand corner of the rectangle
corresponds to the number on the left hand corner directly opposite.

A few concrete examples will illustrate the rectangle method of
working problems in standardization.

Problem I. How many pounds of 23 % cream and 3 % milk will be
required to make 500 pounds of an 18% cream? Using our diagram
as described above we have the following results:

18

15-'

These results mean that if five pounds of 3% milk were mixed with
15 pounds of 23% cream the result will be 20 pounds of a mixture
testing 1 8%. The amount of the mixture desired was 500 pounds,
which is twenty-five times the amount obtained with the rectangle
method (500 -r- 20 = 25). If we multiply the numbers on the upper
and lower right hand corners of the rectangle by twenty-five we will
obtain respectively the pounds of 23% cream and 3% milk required
to make 500 pounds of an 18% mixture. These are 375 pounds of
23% cream (15 x 25 = 375), and 125 pounds of 3% milk (5 x 25 =
125).

The problem may also be worked by simple proportion:
5:20 :: X : 500

2OX = 25OO

X = 1 2 5 pounds of 3 % milk.
15:20 :: X : 500

2oX = 7500
X = 375 pounds of 23% cream.

IO

In the above problems the amount of the mixture desired is
definite.

In working problems in standardization it is wisest to prove the
answer as this will show if the results are correct. While proving
a problem will point out errors it will not show where mistakes have
been made. The proof of the above problem is as follows:

Proof:

It is desired to make 500 pounds of an 18% mixture which would
necessarily contain 90 pounds of fat (500 X .18 = 90). According to
our computations the 500 pounds of 18% cream will consist of 125
pounds of 3 % milk and 375 pound s of 2 3 % cream . If these material s
furnish 90 pounds of fat, the problem is worked correctly. One
hundred twenty-five pounds of 3% milk will contain 3.75 pounds of
fat: (1.25 X .03 = 3.75). Three hundred seventy-five pounds of
23% cream will contain 86.25 pounds of fat (375 X .23 = 86.25),
86.25 + 3-75 = 90 pounds of fat.

In the following problem the amount of mixture to be made up
is indefinite.

Problem 2:

How much 23% cream must be mixed with 500 pounds of 3% milk
to make a mixture testing 1 8% ? Using our diagram according to the
directions previously given we have the following results:

£3'

18

15-

5-.

These results mean that we must mix the materials in the proportion
of 15 pounds of 23% cream to five pounds of 3% milk to make an
1 8% mixture. According to the conditions of the problem we must
use 500 pounds of 3% milk which is 100 times as large as the amount
given in the above proportion (500 -=- 5 = 100). The 23% cream and
the 3% milk must be kept in the proportion of 15:5 and if the 3%
milk is increased one hundred times the 23% cream must be increased
the same number of times. This would give 1500 pounds of 23%
cream (15 X 100 = 1500), which should be added to the 500 pounds
of 3% milk, giving 2000 pounds of an 18% mixture. The problem
may also be worked by simple proportion.

15 : 5 " X : 500
5X = 7500

X = 1 500 pounds of 23% cream.
Proof:

The 2000 pounds of 18% cream will contain 360 pounds of fat
(2000 X -18 = 360). According to our results, the 2000 pounds of
1 8% cream is made up of 500 pounds of 3% milk and 1500 pounds of
23% cream. The 500 pounds of 3% milk will contain 15 pounds of
fat (500 X .03 = 15). The 1500 pounds of 23% cream will contain
345 pounds of fat, 345 + 1 5 = 360 pounds of fat, which is the number
of pounds in the mixture.

In the original method of working problems in standardization all
computations are made on a pound basis. From this basis it is easy
to compute the amount of different materials needed to make up any
given quantities of milk or cream. Problems are worked by this
method as follows:
Problem 3.

How much 23% cream must be mixed with 500 pounds of 3% milk
to make a mixture testing 18%?

One pound of 23% cream will contain .23 pounds of fat.
One pound of 3% milk will contain .03 pounds of fat.

The difference is 20 pounds of fat.

Every time one pound of .23% cream is removed and a pound of
3% milk substituted there is removed .20 pounds of fat.
One pound of 23% cream contains .23 pounds of fat.
One pound of 18% cream contains .18 pounds of fat.

The difference is 05 pounds of fat.

It is desired to reduce the fat content .05 pounds of fat for every
pound of the mixture. This is done by the addition of 3% milk
which may in this case be regarded as a reducing agent. Since the
substitution of a pound of 3% milk for a pound of 23% cream reduces
the fat content of a pound mixture .20 pounds of fat and it is desired
to reduce the fat content .05 pounds of fat, it will require as much
of the 3% milk as .20 is contained into .05 or .25 (.05 -r- .20 = 25).
The .25 is the number of pounds of 3% milk there would be in one
pound of an 1 8 % mixture . The remainder . 7 5 pounds (i — .25 = .75),
would be 23% cream. The following simple proportion will give the
number of pounds of 23% cream which must be added to 500 pounds
of 3% milk to make a mixture testing 18% fat.

12

.75 :.as : : X : 500
•25 X = 375
X = 1 500 pounds of 23% cream.

The following problem is an illustration of the original method
of working standardization problems when a definite amount of the
mixture is desired.
Problem 4.

How much 23% cream and 3% milk must be mixed to make a
cream testing 18%? Since the percentages of fat in these problems
are the same as those in Problem 3, the amount of 3% milk in one
pound of an 18% mixture would be the same as already shown, and
therefore needs no further explanation. Since .25 is the number of
pounds of 3% milk in one pound of 18% cream, we would have the
simple proportion:
i:.25 :: 500 : X

X = 125, the number of pounds of 3% milk in an 18% mixture.
The remainder of the mixture, 375 pounds (500 — 125), will be 23%
cream. The cream could, of course, be found by forming the follow-
ing simple proportion.
11.75 :: 500 : X

X = 375 pounds of 23% cream.

NOTE: — In the two following exercises on Standardization it is
intended that one shall consist of a problem where the amount to
be standardized is definite and the other shall be a problem where the
resulting amount is indefinite.

EXERCISE II
STANDARDIZING

1. Test for fat by the Babcock method the samples of milk and
cream to be used in standardization. Report the percentages of
fat found and a definite percentage to which the milk or cream is to
be standardized will be assigned.

2. After standardizing the milk or cream as directed, test it for
fat by the Babcock method in order to verify the accuracy of
work.

14

EXERCISE III

1. Test for fat by the Babcock method, the samples of milk and
cream to be used in standardization. Report the percentages of fat
found and a definite percentage to which the milk or cream is to be
standardized will be assigned.

2. After standardizing the milk or cream as directed, test it for
fat by the Babcock method in order to verify the accuracy of your
work.

STUDENT'S NOTES AND REPORT

PASTEURIZATION

Pasteurization applied to dairy work is the process of heating milk
or cream to a temperature sufficiently high and for a time sufficiently'
long to kill most of the organisms in them. The materials should
then be cooled to a temperature of 50° F. or lower to prevent germ
growth. Cooling the product is just as important a part of the
process as is heating, for if there are any organisms not killed by the
heating process, they will multiply rapidly if the milk or cream is kept
at temperatures favorable for germ growth. Milk or cream from
the market standpoint should be kept at just as low a temperature as
possible and still not freeze them.

Pasteurization has for its purpose two objects, (i) the killing of
pathogenic organisms, and (2) checking germ growth. The first is
the most important, and it is supposed that the process of pasteuriza-
tion is efficient in destroying all pathogenic organisms. This supposi-
tion is based upon a great many experiments on the thermal death
point of such pathogenic organisms as those which cause tuberculosis,
typhoid, and diphtheria.

Pasteurization differs from sterilization in that the latter process
kills all living material in and about an object. It is not possible to
sterilize milk for market purposes because the high temperatures and
length of time required for sterilization change the normal taste of
milk and render it objectionable to the consumer. Too high tempera-
tures also change the chemical composition of milk, the chief of these
changes being the precipitation of albumin and causing the lime salts
to become more insoluble. For these reasons both the degree of heat
and the length of time employed in the process of pasteurization are
limited.

There are two methods of pasteurization one called the flash
method and the other the holder method. In the flash method, milk
is heated to a comparatively high temperature for a short time,
usually 1 60° F. for one minute or less, and frequently the time which
the milk is subjected to the proper temperature is only a few seconds.

In the holder method, milk is heated to a low temperature for a
comparatively long period of time, 140° F. — 145° F. for 30 minutes
being a very common time and temperature employed. The holder
process of pasteurization is considered more efficient than the flash

16

17

method and many boards of health have forbidden the use of the flash
method of pasteurization of milk sold under their jurisdiction.

Pasteurization should never be used as a means of placing dirty
milk upon the market. While the process does kill the micro-
organisms found in milk it does not always destroy their products,
and if badly contaminated milk is pasteurized and placed upon the
market, although its germ content may be small, it may still be unfit
for human consumption.

EXERCISE IV
PASTEURIZATION BY THE HOLDER METHOD

NOTE: — This exercise should be performed in combination with
Exercise V.

1 . Thoroughly mix four cans of milk by pouring from one can to
another. Take in a sterile bottle a small amount of milk from each
can and place the sample on ice until it can be plated for bacteria.
Two of the cans of milk are to be used in Exercise V.

2 . Thoroughly scald the machine. This may be done by running
hot water through the coils. Pasteurize two cans of milk at a tem-
perature of 140° F. for 30 minutes. After heating the milk for the
proper time at the proper temperature, cool the milk to as low a
temperature as possible in the time allowed and lower the temperature
of the milk as rapidly as possible. Carefully record the weights of
the milk used, the time required to raise the milk to 140° F., the
temperature to which the milk was cooled, the temperature of the
refrigerating substance as it enters the coils, and the time required for
the entire process.

When the process is complete, take in a sterile bottle a sample
of the milk to be plated for bacteria. Compare the bacteria counts
obtained with that of the raw milk, and that from the milk pas-
teurized by the flash method.

i8
STUDENT'S NOTES AND REPORT

EXERCISE V
PASTEURIZATION BY THE FLASH METHOD

NOTE: — This exercise should be performed in combination with
Exercise IV.

1. Thoroughly scald the machine. This may best be done by
allowing water to pass through the machine and turning on the steam
at the same time. Allow this hot water to pass over the cooler and
so far as possible sterilize it. Use for this experiment the two cans
of milk, mixed as directed in Exercise IV. Pasteurize the milk at a
temperature of 160° F. Carefully record the pounds of milk used,
time required for the process, temperature of refrigerating material
as it enters and leaves the cooler and the temperature to which the
milk is cooled.

2. Take in a sterile bottle a sample of the milk to be plated for
bacteria. Compare the count obtained with that of the raw milk
and that obtained from the milk pasteurized by the holder method.

2O

STUDENT'S NOTES AND REPORT

21

EXPLANATION OF EXERCISE VI

On the average dairy farm, one of the most practical methods of
cooling milk is to set the can containing the milk in a tank of ice water.
For this purpose a cement tank is the most durable and in the long run
cheapest. The walls of the tank should be from four to six inches
thick and that side on which the milk is lifted in and out of the tank
should be faced with iron to prevent the cans from chipping the
cement. The tank will be most convenient if it is sunk in the floor
as this will make it easier to lift the cans in and out. The walls
should, however, extend about twelve inches above the floor to pre-
vent dirt working into the tank. An outlet should be made in the
bottom of the tank so that it may be easily cleaned as more or less
milk will be spilled, causing the tank to become unsanitary.

A galvanized iron tank, useful in cooling milk and capable of hold-
ing four cans, may be purchased from dairy supply houses for from
eight to ten dollars.

In order to have milk cool properly in a tank of this kind it is
necessary to frequently stir the milk in the cans. Unless milk is
stirred frequently it will not cool rapidly and rapid cooling is essential
in preventing an increase of germ life.

The purpose of the following exercise is to show the effect of stirring
at different intervals on the rapidity with which milk cools. The
student should also draw conclusions regarding the frequency with
which milk should be stirred to get the best practical results.

EXERCISE VI
COOLING MILK IN CANS

1. Heat four cans of milk to 95° F. and place in a tank of ice
water. For this experiment about 135 pounds of ice will be required.

Stir can No. I every five minutes and record the temperature.

Stir can No. II every ten minutes and record the temperature.

Stir can No. Ill continuously and record the temperature every
ten minutes.

Do not stir can No. IV at all but record the temperature of the
milk in the center at ten minute intervals.

2. Carry on the experiment for one hour and at the end of one
hour thoroughly stir can No. IV and record the temperature of the
mixed milk with that of the temperature of the milk before the
milk was thoroughly stirred.

3 . Compare the temperature obtained in the four different cans.
Draw conclusions concerning the frequency with which milk should
be stirred, to get the best practical results.

22

STUDENT'S NOTES AND REPORT

23

EXPLANATION OF EXERCISE VII

There are several kinds of conical coolers on the market, which are
suitable for use on farms. These coolers furnish an efficient piece
of apparatus at a reasonable price. Their use has often been abused
since they are frequently stationed and used in places where they are
exposed to dust and dirt, and in order to minimize the danger from
such contamination, some coolers are provided with a hood which
surrounds that part of the cooler over which the milk flows. The
refrigerating material most commonly used in these coolers is ice and
water, although they may be attached to a brine barrel or a running
water supply, if such a supply is available. Whatever the refrigerating
substance used in these coolers, it should be stirred frequently. If it
is not stirred, the refrigerating material next to the walls soon becomes
warmed by the milk passing over the cooler and so loses its efficiency.
The purpose of the following experiment is to compare the effi-
ciency of a conical type of cooler when the refrigerating material
inside the cooler is stirred and when it is not stirred.

EXERCISE VII
COOLING MILK WITH A CONICAL COOLER

1 . Weigh a can of whole milk and heat it to 95° F. The purpose
of heating the milk is to bring it to nearly the same temperature as
when drawn from the cow. Place forty pounds of ice inside the cooler
and fill the cooler to the overflow pipe with cold water. Run the
milk over the cooler and note the time it takes the first milk which
comes from the receiving tank to reach the outlet spout of the cooler.
Do not stir the water inside the cooler. Record the temperature of
the milk at the outlet spout every three minutes. Note the time
required to pass the milk over the cooler. After all of the milk has
passed over the cooler, stir it thoroughly and record the final tempera-
ture. Take the temperature of the water near the walls of the cooler.
Stir the water and then take its temperature. Weigh the amount of
ice left.

2 . Repeat the experiment, heating the milk to the same tempera-
ture and using the same amount of ice, but in this case stir the ice
water in the cooler continuously. Record the temperature of the
milk every three minutes. Stir the can of milk and take the final
temperature. Weigh the amount of ice left. Compare the results
obtained by the two methods of cooling. Make a drawing of the
cooler. Compute the capacity of the cooler per hour.

State in your notes the name of the cooler used.

24
STUDENT'S NOTES AND REPORT

COMPUTING AMOUNT OF ICE NECESSARY TO COOL A
GIVEN AMOUNT OF MILK

The study of refrigeration is essentially a study of heat. The unit
of heat used by refrigeration engineers is called the British Thermal
Unit, and it is the amount of heat required to raise one pound of water
one degree Fahrenheit at its maximum density, 39.1° F.

Not all substances require the same amount of heat to raise their
temperature per unit of mass. Water is taken as a standard, and the
ability of a substance to absorb heat in comparison with water is
called the specific heat of the substance. The specific heat of water
is called i , and most substances have a specific heat less than that of
water. The specific heat of milk is variable, depending to a large
extent upon the temperature and the variation in fat content. The
lower the fat content the higher the specific heat. The specific heat
of normal milk is variously given by different investigators as ranging
between .92 and .95. In computations on refrigeration, the melting
point of ice is used as a basis, because this is definite and constant. It
requires 144 B. T. U. to melt one pound of ice, and knowing this fact,
the amount of ice necessary to cool a given amount of milk may be
readily computed. The method of computation may best be illus-
trated by a specific problem.

How many pounds of ice will be required to cool 500 pounds of
milk from 80° F. to 32° F. ? In this case, the specific heat of the milk
is considered as .93.

Five hundred X .93 = 465, the number of heat units required
to raise the 500 pounds of milk one degree as compared with the same
amount of water. Since the milk is to be cooled 48° F. (80 — 32 =48)
multiplying 465 by 48 will give 22,320 heat units to be extracted from
the milk, (465 X 48 = 22,320). Since it requires 144 B. T. U. to
melt one pound of ice, it would require as many pounds of ice to cool
the 500 pounds of milk as 144 is contained in 22,320, or 155, (22,320 -f-

*44 = 155)-

If the milk is cooled to a temperature above 32° F. the available
refrigeration of one pound of ice is increased and the difference
between 32° F. (the temperature of the melting ice), and the tempera-
ture to which the milk is cooled, must therefore be added to the
B. T. U. necessary to melt a pound of ice (144).

25

26

For example, suppose we wished to find the number of pounds
of ice necessary to cool 500 pounds of milk from 80° F. to 40° F.
Assuming the specific heat of the milk to be .93, the number of heat
units to be extracted from the milk would be 500 X .93 X 40 (80 — 40
= 40) = 18,600. Since the milk is to be cooled to a point 8° F. above
the melting point of ice (40 — 32 = 8), the available refrigeration of a
pound of ice would be increased to 152 (144 + 8 = 152). The num-
ber of pounds of ice necessary would therefore be 1 8 ,600 -f- 152 = 122.3
pounds.

The theoretical amount of ice will usually be insufficient to cool
milk to the desired temperature. This is because of outside influences
such as temperature of the air, temperature of the water with which
the ice is mixed, and temperature of the apparatus through which the
water is run.

EXPLANATION OF EXERCISE VIII

Lower temperatures may be obtained with a mixture of salt and
ice than with ice alone. This is because of the fact that when two
solids unite to form a liquid, they absorb heat. Within certain limits
the larger the percentage of salt used, the lower the temperature that
can be obtained. After a certain amount of salt has been added the
solution becomes saturated and the further addition of salt has no
effect in lowering the temperature.

The following table from B. A. I. Bulletin No. 98 gives the approxi-
mate temperatures which may be obtained with different percentages
of salt and ice.

Percentage of salt in Temperature of % of salt in Temperature of salt

mixture mixture mixture m mixture

op op

o 32 15 ii

5 27 20 1.5

10 20 25 -IO

27

EXERCISE VIII
COMPARATIVE EFFICIENCY OF ICE WATER AND BRINE AND ICE

Use for this experiment a Tubular cooler.

Heat two cans of milk to Q5°F. The purpose of heating the milk
to this temperature is to have it nearly the same temperature as when
drawn from the cow. Weigh the amount of milk used. Weigh out
about 125 pounds of ice. Crush it and place it in the brine barrel.
Run in cold water until the barrel is about half full. Stir the mixture
of ice and water. Allow the pump to run for about two minutes or
until the temperature of the water in the barrel is 32° F. before run-
ning the milk over the cooler. Then run the milk over the cooler at
its full capacity. Record the length of time required to cool the milk
and take the temperature of the milk at the outlet faucet every three
minutes. Thoroughly stir the milk in the can and record the final
temperature. Record the temperature of the return water from the
cooler every three minutes. Weigh the amount of ice left.

Repeat the experiment, heating the milk to 95° F. and using the
same amount of ice. The ice left from the previous experiment
may be used in this one. Add 40 pounds of salt to the mixture in this
barrel and thoroughly stir until the salt is dissolved. The amount
of salt required will depend somewhat on its quality. If it is insoluble,
more will be required. Have the temperature at 28° F. to 30° F.
Take temperature of the milk every three minutes, the temperature
of the return water every three minutes, and the final temperature of
the milk in the can. Weigh the amount of ice left. Draw diagram
of the cooler, and figure out its capacity per hour. Show in drawing
the relative position of the cooler, brine barrel, and pump.

28

STUDENT'S NOTES AND REPORT

Heat to a temperature of 95° P., two cans of milk. Weigh out
125 pounds of ice, crush it, and place it in the brine barrel which has
previously been filled about half full of cold water. Add, in salt, to
the ice water in the barrel, 5% of the weight of the ice. Thoroughly
mix the salt and ice water in the barrel and pump the brine through
the cooler, noting its temperature before starting to cool the milk.

Cool the milk and take the temperature of the mixed milk after
cooling. Also take the temperature of the brine as it comes from the
cooler. Weigh the ice if any is left, and save it for use in the second
part of the experiment.

Remove all of the brine from the barrel and flush out the barrel
and cooler by pumping cold water through them. Repeat the above
experiment using 1 5% of salt instead of 5%. Record all temperatures
the same as in the first part of the experiment.

30
STUDENT'S NOTES AND REPORT

THE DAIRY SCORE CARD

The dairy score card is a card on which are enumerated the good
points which a dairy should possess, and these points are given
numerical values. The score card is divided into two distinct
divisions, equipment and method. Out of a possible 100 points for a
perfect score, 40 are given to equipment and 60 to methods. This
numerical division is made to give a just recognition to the importance
of proper methods in the production of clean milk. Good equipment
should be an aid in clean milk production, and other things being
equal, a dairyman will produce better milk with good equipment than
with poor equipment. However, good equipment without proper
method will not produce wholesome milk.

Those who use the score card should not regard it as an infallible
set of rules from which no deviation should ever be made. It is
simply a guide to help the producer to see the conditions of his dairy
and to help the inspector to judge intelligently of those conditions.

The chief value of the score card is that when properly used it is
educational, and it is educational because it not only points out
defects, but it emphasizes the seriousness of these defects. In this
way the dairyman is given a chance to improve in these things which
will aid most in clean milk production.

32

EXPLANATION OF EXERCISES X, XI AND XII

Score dairies according to the official score card, and place the
score of the different points on the card. In the blank page reserved
for notes, write a short criticism of the place scored, and note those
things which might be done to improve the milk supply, and at the
same time would not require a big outlay of capital. Also criticise
the methods employed, in the same way.

NOTE : — It is intended that at least three dairies of different grade
should be scored, one having excellent buildings and equipment, one
having medium buildings and equipment, and one having poor
buildings and equipment. It would be desirable if the high grade
dairy was producing certified milk, or milk of similar grade, and the
poorly equipped dairy was producing a good grade of milk by means of
superior methods. This would emphasize the importance of clean
milk production. If time permits, more than three dairies may be
scored, as it is highly desirable that all the practice possible be given
to this part of clean milk production.

EXERCISE X
JUDGING DAIRY BARNS

1. Score according to the official score card the dairy visited.
Place the score allowed the different points on the score card.

2. On the sheet allotted to notes, write a brief criticism of the
dairy and the methods employed. Pay particular attention to those
things which are important in clean milk production, and at the same
time would not require a big outlay of capital.

STUDENT'S NOTES AND REPORT

SCORE

EQUIPMENT

SCORE

METHODS

SCORE

Perfect

Allowed

Perfect

Allowed

cows

6

cows
Clean

8
6

5

I

Apparently in good health .... I

Free from visible dirt 6

STABLE

If tested with tuberculin within a
year and no tuberculosis is found,
or if tested within six months and
all reacting animals removed . . . . 5
If tested within a year and reacting
animals are found and removed 3

Floor ... 2

Walls r

Water, clean and fresh

i

Mangers and partitions i

STABLES

Location of stable

3

Freedom from odors 2

Well drained I

4

4

i
7

I
I

5

i

Cleanliness of bedding

Free from contaminating surround-
ings i

Barnyard

2

Clean . . i

2

Tight, sound floor and proper gutter2
Smooth, tight walls and ceiling. . . . i
Proper stall, tie, and manger i
Provision for light: Four sq. ft. of
glass per cow

Removal of manure daily

To 50 feet or more from stable.

MILK ROOM OR MILK HOUSE

Cleanliness of milk room

3

8

9

Three sq. ft., 3; 2 sq. ft., 2; i sq. ft'.
i. Deduct for uneven distribution.

Ventilation

UTENSILS AND MILKING

Care and cleanliness of utensils
Thoroughly washed 2

Provision for fresh air, controllable
flue system 3

Windows hinged at bottom, 1.50:
sliding windows i ; other openings .50.
Cubic feet of space per cow, 500 feet3
Less than 500 ft. , 2 ; less than 400 ft. ,
i; less than 300 ft., o.
Provision for controlling tempera-
ture i

Sterilized in steam for 15 minutes. . . .3
Placed over steam jet or scalded with
boiling water, 2.
Protected from contamination 3
Cleanliness of milking

UTENSILS

Construction and condition of utensils
Water for cleaning

Clean, dry hands 3

Udders washed and wiped 6

Udders cleaned with moist cloth, 4 ;
cleaned with dry cloth or brush at least
15 minutes before milking, i.

HANDLING THE MILK

Cleanliness of attendants in milk room
Milk removed immediately from stable
without pouring from pail . ...

Clean, convenient and abundant.
Small-top milking pail

Milk cooler

Clean milkinp suits. .

i

MILK ROOM. OR MILK HOUSE

Location free from contaminating sur-
roundings

i

2

Cooled immediately after milking each

Cooled below 50° F

5
3

2

Si° to 5S°, 4; 56° to 60°, 2.

Construction of milk room .

51° to 55°, 2; 56° to 60°, i.
Transportation below 50° F

Floor, walls and ceiling i

I
I

Separate rooms for washing utensils
and handling milk

Si° to 55°, i-So; 56° to 60° I.

If delivered twice a day allow perfect
score for storage and transportation.

Total

Facilities for steam Hot water 0.5. ...
Total

40

60

Equipment.

+ Methods = Final Score.

NOTE i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be
further limited.

NOTTS 2 — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan-
gerous disease in animals or attendants, the score shall be o.

SANITARY INSPECTION OF DAIRY FARMS

MARKET MILK PRODUCTION

SCORE CARD

*

Indorsed by the Official Dairy Instructors' Association.

Owner or lessee of farm :

P. O. address .State

Total number of cows Number milking

(jallonsof milk produced daily

Product is sold by producer to families, hotels, restaurants, stores,

•v

to dealer

For milk supply of

Permit No Date of inspection 191 ..

REMARKS. .

(Signed)

Inspector

43

35

EXERCISE XI
JUDGING DAIRY BARNS

1. Score according to the official score card,' the dairy visited.
Place the score allowed the different points, on the score card.

2. On the sheet allotted to notes, write a brief criticism of the
dairy and the methods employed. Pay particular attention to those
things which are important in clean milk production, and at the same
time would not require a big outlay of capital .

STUDENT'S NOTES AND REPORT

SCORE

EQUIPMENT

SCORE

METHODS

SCORE

Perfect

Allowed

Perfect

Allowed

cows

Hoaltti

6

i

cows
Clean

8
6

S

i

Free from visible dirt 6

STABLE

Cleanliness of stable

If tested with tuberculin within a
year and no tuberculosis is found,
or if tested within six months and
all reacting animals removed . . . . 5
If tested within a year and reacting
animals are found and removed 3
Food clean and wholesome

Floor 2

Walls i

Ceiling and ledges i

Water, clean and fresh

i

Mangers and partitions i

STABLES

Location of stable

2

Windows i

Stable air at milking time

Freedom from dust 3

Freedom from odors 2

Well drained i

4

4

I
7

i

i

S
I

Cleanliness of bedding

Free from contaminating surround-
ings i

Barnyard

2

Construction of stable

2

Tight, sound floor and proper gutter2
Smooth, tight walls and ceiling. . . . i
Proper stall, tie, and manger i
Provision for light: Four sq. ft. of
glass per cow

Wei! drained i

Removal of manure daily

MILK ROOM OR MILK HOUSE

Cleanliness of milk room

3

8
9

2

Three sq. ft., 3; 2 sq. ft., 2; I sq. ft.,
i. Deduct for uneven distribution.

Ventilation

UTENSILS AND MILKING

Care and cleanliness of utensils
Thoroughly washed 2

Provision for fresh air, controllable
flue system . •;

Windows hinged at bottom, 1.50
sliding windows i ; other openings .50.
Cubic feet of space per cow, 500 feet3
Less than 500 ft., 2; less than 400 ft.,
i; less than 300 ft., o.
Provision for controlling tempera-
ture . . i

Sterilized in steam for 15 minutes ... .3
Placed over steam jet or scalded with
boiling water, 2.
Protected from contamination 3

UTENSILS

Construction and condition of utensils
Water for cleaning

Clean, dry hands •?

Udders washed and wiped 6
Udders cleaned with moist cloth, 4;
cleaned with dry cloth or brush at least
15 minutes before milking, i.

HANDLING THE MILK

Cleanliness of attendants in milk room

Clean, convenient and abundant.
Small-top milking pail

M ilk cooler

Clean milkinp suits

I

Milk removed immediately from stable

MILK ROOM. OR MILK HOUSE

Location free from contaminating sur-
roundings

I

2

Cooled immediately after milking each

2

5
3

2

Cooled below 50° F

51° to 55°, 4; 56° to 60°, 2.

Construction of milk room

51° to 55°, 2; 56° to 60°, i.
Transportation below 50° F

Floor, walls and ceiling i

I
I

Separate rooms for washing utensils
and handling milk

51° to 55°, 1.50; 56° to 60° i.

If delivered twice a day allow perfect
score for storage and transportation.

Total

Facilities for steam Hot water 0.5 ....
Total

40

60

Equipment..

-f- Methods = Final Score..

NOTE i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be
further limited.

NOTE * — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan-
gerous disease in animals or attendants, the score shall be o.

SANITARY INSPECTION OF DAIRY FARMS

MARKET MILK PRODUCTION

SCORE CARD

Indorsed by the Official Dairy Instructors' Association.

Owner or lessee of farm

P. O. address State

Total number of cows Number milking

Gallons of milk produced daily

Product is sold by producer to families, hotels, restaurants, stores,

to dealer

For milk supply of.

Permit No.. Date of inspection 191 . .

REMARKS. .

(Signed)

Inspector

38

EXERCISE XII
JUDGING DAIRY BARNS

1. Score according to the official score card, the dairy visited.
Place the score allowed the different points, on the score card.

2. On the sheet allotted to notes, write a brief criticism of the
dairy and the methods employed. Pay particular attention to those
things which are important in clean milk production, and at the same
time would not require a big outlay of capital.

STUDENT'S NOTES AND REPORT

SCORE

EQUIPMENT

SCORE

METHODS

SCORE

Perfect Allowed

Perfect

Allowed

cows
Health

6

i

cows
Clean

8
6

5

i

Apparently in good health . I

STABLE

Clsanliness of stable

If tested with tuberculin within a
year and no tuberculosis is found,
or if tested within six months and
all reacting animals removed .... 5
If tested within a year and reacting
animals are found and removed 3
Food clean and wholesome

Floor 2

Walls i

Ceiling and ledges i

Water, clean and fresh

i

Mangers and partitions i
Windows i

STABLES

Location of stable

2

Stable air at milking time

Freedom from odors 2

Well drained I

4

4

I

7

I
I

Cleanliness of bedding

Free from contaminating surround-
ings . i

Barnyard

2

Construction of stable

Clean i

-

Tight, sound floor and proper gutter:
Smooth, tight walls and ceiling. . . . )
Proper stall, tie, and manger ]
Provision for light: Four sq. ft. o!
glass per cow

Well drained . . i

To 50 feet or more from stable.

MILK ROOM OR MILK HOUSE

Cleanliness of milk room

3

8

9

2

Three sq. ft.. 3; 2 sq. ft., 2; I sq. ft.
I. Deduct for uneven distribution.

Ventilation

UTENSILS AND MILKING

Care and cleanliness of utensils
Thoroughly washed 2

Provision for fresh air, controllabl.
flue system . .

Windows hinged at bottom, 1.50
sliding windows i; other openings .50
Cubic feet of space per cow, 500 feet.
Less than 500 ft. , 2 ; less than 400 ft. .
i; less than 300 ft., o.
Provision for controlling tempera-
ture i

Sterilized in steam for 15 minutes. . . .3
Placed over steam jet or scalded with
boiling water, 2.
?rotected from contamination 3
Cleanliness of milking

UTENSILS

Construction and condition of utensils
Water for cleaning

Udders washed and wiped 6

Udders cleaned with moist cloth, 4 ;
:leaned with dry cloth or brush at least
15 minutes before milking, i.

HANDLING THE MILK

Cleanliness of attendants in milk room
Milk removed immediately from stable

Clean, convenient and abundant.
Small-top milking pail

5

i

M ilk cooler

Clean milking suits

i
i

2

MILK ROOM. OR MILK HOUSE

Location free from contaminating sur-
roundings

Cooled immediately after milking each

2

s

3

2

Cooled below 50° F . .

51° to 55°, 4; 56° to 60°, 2.

Construction of milk room

Si° to 55°, 2; 56° to 60°, i.
Transportation below <;o0 F

Floor, walls and ceiling ". . i

I
I

Separate rooms for washing utensils
and handling milk

51° to 55°, i-So; 56° to 60° i.

If delivered twice a day allow perfect
score for storage and transportation.

Total ....

•

Facilities for steam Hot water 0.5 ....
Total . .

40

60

Equipment..

+ Methods = Final Score.

NOTE i — If any exceptionally filthy condition is found, particularly dirty utensils, the total score may be
further limited.

NOTE 2 — If the water is exposed to dangerous contamination, or there is evidence of the presence of a dan-
gerous disease in animals or attendants, the score shall be o.

SANITARY INSPECTION OF DAIRY FARMS

MARKET MILK PRODUCTION

SCORE CARD

Indorsed by the Official Dairy Instructors' Association.

Owner or lessee of farm -

P. O. address State

Total number of cows Number milking

Gallons of milk produced daily

Product is sold by producer to families, hotels, restaurants, stores,

to dealer

For milk supply of

Permit No Date of inspection 191 . .

REMARKS. .

(Sinned)

Inspector

41

EXERCISE XIII
JUDGING CITY MILK PLANT

1. Judge according to the official score card, a city milk plant.
Place the scores allowed on the card.

2. On the sheet allotted to notes, write a brief criticism of the
plant and the methods employed. Note especially the arrangement
of the plant as regards convenience for performing work. Also note
the location and condition of the plant in regard to its sanitary sur-
roundings. Point out any improvements either in equipment or
methods which would be beneficial and at the same time require only
a small outlay of capital.

STUDENT'S NOTES AND REPORT
SANITARY INSPECTION OF CITY MILK PLANTS

Owner or manager .......................................... Trade name .

City .................... Street and No ........................ State . . .

f Milk ..... . .......

Number of wagons .................. Gallons sold daily <

Cream

Permit or License No Date of inspection , 191

EQUIPMENT

SCORE

METHODS

SCORE

Perfeit

Allowed

Perfect

Allowed

BUILDING:
Location: Free from contaminating

2

BUILDING

15

Cleanliness:
Floors . 3

16
16

9

4

6
8

20

Walls . . i

Shafting, pulleys, hangers, pipes, i

Freedom from flies and other insects 3
Drainage 2

Construction

Floors tight, sound, cleanable t
Walls tight, smooth, cleanable . . . . i
Ceilings smooth, tight, cleanable. . i
Provision for light i

APPARATUS

Cleanliness:
Thoroughly washed and rinsed . . 6
Sterilized in live steam, thirty
minutes . 5

Provision for pure air I

(Thoroughly scaled after
washing with water over
200° F. or live steam, 3.)

Minimum of shafting, pulleys, hang-
ers, exposed pipes, etc i

APPARATUS . '.

Boiler 2

2

Hot- water heater i

HANDLING MILK

Received below "50° F 5

Appliances for cleansing utensils anc

(50°-55°, 4: 55°-6o°, 3.)
Rapidity of handling in plant 3

Racks, etc., for utensils and bottles

Freedom from undue exposure to air
in the plant 2

Sterilizer for utensils and bottles . . 2
Bottling and capping machine i
Wash bowl, soap, and towel for

Capping bottles by machine. i

Bottle top and cap protected by
covering 2

RtoraTe 45° F. or below 3

Protection during delivery 2

(45°-SO°, 2; 50°-S5°. i.)
INSPECTION

Condition of apparatus (make deduc-
tion for inaccessible parts, open
seams, rusty ware, decayed or
battered tables or sink, milk-
carrying pipes with rough interiois
and lack of frequent hand coup-
lings, and for badly worn and
poorly repaired material) 4
LABORATORY AND EQUIPMENT

Inspection of dairies supplying milk 5
(Once a year, i ; twice a year, 2 ;
three times a year, 3; four
times a year, 4.)

MISCELLANEOUS ...

Cleanliness of attendants 2

Clean, fresh i

(General appearance, hands, etc.,
i ; clean, washable clothing, i.)

Convenient and abundant i

Total

Total

40

00

Score for equipment plus score for methods equals TOTAL SCORE

NOTE — If the conditions in any particular are so exceptionally bad as to be inadequately expressed by a
score of "o" the inspector can make a deduction from the tct il score.

, Inspector.

43

EXERCISE XIV
JUDGING CITY MILK PLANT

1. Judge according to the official score card, a city milk plant.
Place the scores allowed on the card.

2. On the sheet allotted to notes, write a brief criticism of the
plant and the methods employed. Note especially the arrangement
of the plant as regards conveniences for performing work. Also note
the location and condition of the plant in regard to its sanitary sur-
roundings. Point out any improvements either in equipment or
methods which would be beneficial and at the same time require only
a small outlay of capital.

STUDENT'S NOTES AND REPORT
SANITARY INSPECTION OF CITY MILK PLANTS

Owner or manager Trade name .

City Street and No State . . .

f Milk

Number of wagons Gallons sold daily <

[ Cream

Permit or License No Date of inspection ,191

EQUIPMENT

SCORE

METHODS

SCORE

Perfect

Allowed

Perfect

Allowed

BUILDING:

Location: Free from contaminating
surroundings

2

BUILDING

15

Cleanliness:
Floors .3

16

•

16

9

4

Arrangement

6

8

Walls . i

Separate receiving room i
Separate handling room 2

Ceilings ... . . 2

Shafting, pulleys, hangers, pipes, i

Freedom from flies and other insects 3
Drainage 2

Construction

Floors tight, sound, cleanable i
Walls tight, smooth, cleanable . . . . i
Ceilings smooth, tight, cleanable . . I

APPARATUS

Cleanliness:
Thoroughly washed and rinsed. .6
Sterilized in live steam, thirty
minutes 5

Minimum of shafting, pulleys, hang-

(Thoroughly scaled after
washing with water over
200° F. or live steam, 3.)

APPARATUS :

Boiler 2

2

HANDLING MILK

Received below 50° F 5

Appliances for cleansing utensils and

(50°-55°, 4; SS°-6o°, 3.)
Rapidity of handling in plant 3

Racks, etc., for utensils and bottles

Freedom from undue exposure to air
in the plant 2

Sterilizer for utensils and bottles . . 2
Bottling and capping machine i

Capping bottles by machine i

Bottle top and cap protected by
covering 2

Wash bowl, soap, and towel for

Storage 45° F. or below 3

Protection during delivery 2

(4S°-50°, 2; SO°-SS°, i.)
INSPECTION

Condition of apparatus (make deduc-
tion for inaccessible parts, open
seams, rusty ware, decayed or
battered tables or sink, milk-
carrying pipes with rough interiors
and lack of frequent hand coup-
lings, and for badly worn and
poorly repaired material) 4
LABORATORY AND EQUIPMENT

Bacteriological work 4

Inspection of dairies supplying milk 5
(Once a year, i ; twice a year, 2 ;
three times a year, 3; four
times a year, - 4.)

M ISCELLANEOUS

Cleanliness of attendants 2

WATER SUPPLY

2

Clean, fresh i

(General appearance, hands, etc.,
i; clean, washable clothing, i.)
Cleanliness of delivery outfit 2

Convenient and abundant i

Total

Total

40

60

Score for equipment plus score for methods equals TOTAL SCORE

NOTE — If the conditions in any particular are so exceptionally bad as to be inadequately expressed by a
score of "o" the inspector can make a deduction from the total score.

, Inspector.

45

EXPLANATION OF EXERCISES XV AND XVI

The ability to judge the flavor and odor of milk and cream requires
considerable practice. There are people whose sense of taste and
smell is not sufficiently acute to enable them to become good milk and
cream judges. Persons who have these two senses developed to at
least a normal degree can, by practice, become very proficient in
detecting odors and flavors in dairy products.

The first thing to note in judging milk or cream is the visible dirt.
The sediment found in milk is usually heavier than the other contents
of the bottle, and therefore sinks to the bottom of the package. The
dirt is detected by raising the bottle above the eye and noting the
sediment resting on the bottom. In order to judge milk or cream
properly, the container should be left undisturbed for at least an hour,
to give sediment plenty of time to settle. In raising the bottle above
the eye, great care should be taken not to agitate the contents and so
drive the dirt into suspension. A reading glass or hand lens is useful
in aiding one to detect sediment in a bottle of milk or cream.

The package and seal should be judged before the latter is dis-
turbed, and before breaking the seal the contents of the bottle should
be well shaken so that the milk or cream will be thoroughly mixed for
bacteriological and chemical analysis. Bacteriological examination
should be made as soon as the package is opened before the milk or
cream becomes contaminated in any way. In milk and cream con-
tests, several bottles of the same lot of milk are entered and one of
these is reserved for bacteriological analysis.

After judging the package for appearance, the sample is next
examined for flavor and odor. In judging for flavor and odor it
is best to warm the sample slightly, as a low temperature disguises
odors and flavors in milk or cream.

In order to keep the sense of taste acute it is necessary to rinse out
the mouth with warm water after tasting each sample.

46

EXERCISE XV'
JUDGING MILK

i . Judge according to the official score card, the samples of milk
furnished. If enough score cards are not available, the page allotted
to notes mlay be ruled off and used to record the scores of the different
samples. Before beginning the work of this exercise, read carefully
the directions on the back of the score card and those on page

NOTE : — Plating milk for bacteria involves considerable time and
labor. If it is impossible to plate the samples judged, the bacteria
score may be called perfect, and the milk judged according to the
other points on the card. This will not give the true quality of the
milk, but it will give the student practice in methods of judging which
is the prime purpose of this exercise. This is particularly true in
regard to detecting flavors and odors.

DEPARTMENT OF DAIRY INDUSTRY

SCORE CARD FOR MILK

Place

Exhibit No .

Exhibitor

Address.

Date,

ITEM

PERFECT
SCORE

SCORE
ALLOWED

REMARKS

Bacteria found per \

Flavor and odor . . .

35
25

10
10

10

5

c

cubic centimeter J
( Flavor

( Odor

V isible dirt
Pit

Per cent found

Per cent found

Per cent found

Bottle and cap

j Cap

Total

IOO

( Bottle

(Signed) .

...191

47

Judge

DIRECTIONS FOR SCORING

BACTERIA PER CUBIC CENTIMETER— PERFECT SCORE, 35

POINTS

Less than 400 35

400 to 700 34.5

700 to i ,000 34

1,000 to 2,000 33.5

2,000 to 3,000 33

3,000 to 4,000 32.5

4,000 to 5,000 32

5,000 to 6,000 31.5

6,000 to 7,000 31

7,000 to 8,000 30.5

8,000 to 9,000 30

9,000 to 10,000 29

10,000 to 15,000 28

15,000 to 20,000 27

20,000 to 25,000 26

25,000 to 30,000 25

30,000 to 35,000 24

35,000 to 40,000 23

40,OOO tO 45.OOO 22

45,000 to 50,000.

POINTS

55,000 to 60,000 i9-
60,ooo to 65,000 18

65,000 to 70,000 17

70,000 to 75,000 16

75,000 to 80,000 15

80,000 to 85,000 14

85,000 to 90,000 13

90,000 to 95,000 12

95,000 to 100,000. II

100,000 to 110,000 10

1 10,000 to 1 20,000 o-

120,000 to 130,000 8

130,000 to 140,000 7

140,000 to 150,000 6-

150,000 to 160,000 5

160,000 to 170,000 4

170,000 to 180,000 i

180,000 to 190,000 2

190,000 to 200,000 i

200,000 and over o-

50,000 to 55,000 2C

NOTE — When the number of bacteri per cubic centimeter exceeds the local legal limit th&
score shall be o.

FLAVOR AND ODOR, PERFECT SCORE, 25

Deductions for disagreeable or foreign odor or flavor should be made according to conditions,
found. When possible to recognize the cause of the difficulty it should be described under Remarks.

VISIBLE DIRT— PERFECT SCORE, 10

Examination for visible dirt should be made only after the milk has stood for some time un-
disturbed in any way. Raise the bottle carefully in its natural, upright position, without tip-
ping, until higher than the head. Observe the bottom of the milk with the naked eye or by the
aid of a reading glass. The presence of the slightest movable speck makes a perfect score im-
possible. Further deductions should be made according to the amount of dirt found. When
possible the nature of the dirt should be described under Remarks.

FAT IN MILK— PERFECT SCORE, 10

POINTS 1 POINTS

4.0 per cent and over 10 i 3.4 per cent.

3.9 per cent 9.8

3.8 per cent 9.6

3-7 per cent 9.4

3.6 per cent 9.2

3.5 per cent 9

NOTE — New York State legal limit, 3% fat.

3.3 percent. . .
3.2 per cent. . .
3.1 per cent. . .
3.0 per cent. . .

SOLIDS NOT FAT— PERFECT SCORE, 10

POINTS

8.7 per cent and over 10

8.6 per cent 9

8.5 per cent 8

8.4 per cent 7

8.3 per cent 6

8.2 per cent 5

New York State legal limit, 11.5% total solids.

8.1 per cent

8.0 per cent

7.9 per cent

7.8 per cent

Less than 7.8 per cent.

POINTS
4
3.

ACIDITY— PERFECT SCORE. 5

Less than 0.2 per cent

0.2 per cent to 0.21 per cent. .
0.21 per cent to 0.22 per cent.

POINTS
S
4
3

POINTS

0.22 per cent to 0.23 per cent 2

0.23 per cent to 0.24 per cent i

0.24 per cent and over o-

BOTTLE AND CAP— PERFECT SCORE, 5

49

EXERCISE XVI
JUDGING CREAM

i . Judge according to the official score card, the samples of cream
furnished. If enough score cards are not available, the page allotted
to notes may be ruled off and used to record the scores of the different
samples. Before beginning the work of this exercise, read carefully
the directions on the back of the score card and those on page.

NOTE : — Plating milk for bacteria involves considerable time and
labor. If it is impossible to plate the samples judged, the bacteria
score may be called perfect and the milk judged according to the
other points on the card. This will not give the true quality of the
milk, but it will give the student practice in methods of judging which
is the prime purpose of this exercise. This is particularly true in
regard to detecting flavors and odors.

SCORE CARD FOR MILK

Place

Class Exhibit No .

ITEM

PERFECT
SCORE

SCORE
ALLOWED

REMARKS

Bacteria found per \

35

cubic centimeter /
i Flavor

Flavor and odor

25

Odor

Visible dirt

IO

Fat

2O

Per cent found

Acidity

e

Per cent found

i Cao

Bottle and cap

5

( Bottle

Total

IOO

Exhibitor

Address.

Date,

(Signed) .

...191

So

Judge

EXPLANATION OF SCORES

BACTERIA PER CUBIC CENTIMETER— PERFECT SCORE, 35

Less than 400

POINTS
35

55,000 and less than 60,000 ....

POINTS

ig

400 and less than 700

34.5

60,000 and less than 65,000 ....

18

700 and less than 1,000

34

65,000 and less than 70,000 ....

.... 17

1,000 and less than 2,000 . .

.... 33.5

70,000 and less than 75,000

16

2,000 and less than 3,000

33

75,000 and less than 80,000 ....

15

3,000 and less than 4,000

32.5

80,000 and less than 85,000 ....

14

4,000 and less than 5,000

32

85,000 and less than 90,000 ....

5,000 and less than 6,000

31.5

90,000 and less than 95,000 ....

12

6,000 and less than 7,000

31

95,000 and less than 100,000 . . .

7,000 and less than 8,000

30.5

100,000 and less than 110,000 . . .

10

8,000 and less than 9,000

30

110,000 and less than 120,000 .

9,000 and less than 10,000 ....

29

120,000 and less than 130,000 . . .

8

10,000 and less than 15,000

28

130,000 and less than 140,000 . . .

7

15,000 and less than 20,000

27

140,000 and less than 150,000 . . .

.... 6

20,000 and less than 25,000

26

150,000 and less than 160,000 . . .

5

25,000 and less than 30,000

25

160,000 and less than 170,000 . . .

4

30,000 and less than 35,000

24

170,000 and less than 180,000 . . .

.... 3

35,000 and less than 40,000 ....

23

180,000 and less than 190,000 . . .

2

40,000 and less than 45,000

22

190,000 and less than 200,000 . . .

I

45,000 and less than 50,000

21

200,000 and over

o

so.ooo and less than aa.ooo . .

2O

FLAVOR AND ODOR, PERFECT SCORE, 25

Deductions for disagreeable or foreign odor or flavor are made according to conditions
found. When possible to recognize the cause of the difficulty it is described under Remarks.

VISIBLE DIRT— PERFECT SCORE, 10

Examination for visible dirt is made only after the milk has stood for some time un-
disturbed in any way. Raise the bottle carefully in its natural, upright position, without tip-
ping, until higher than the head. Observe the bottom of the milk with the naked eye or by the
aid of a reading glass. The presence of the slightest movable speck makes a perfect score im-
possible. Further deductions are made according to the amount of dirt found. When possible
the nature of the dirt is described under Remarks.

FAT IN CREAM— PERFECT SCORE, 20

If 20 per cent fat or above, score perfect. Deduct i point for each one-half per cent
fat below 20.

ACIDITY— PERFECT SCORE, 5

0.2 per cent or less

0.21 per cent or over 0.20.
0.22 per cent or over 0.21 .

POINTS
5
4
3

POINTS

0.23 per cent or over 0.22 a

0.24 per cent or over 0.23 I

Over 0.24 per cent o

BOTTLE AND CAP— PERFECT SCORE, 5

Bottles should be made of clear glass and free from attached metal parts. Caps should be
sealed in their place with hot paraffin, or both cap and top of bottle covered with parchment
paper or other protection against water and dirt. Deductions are made for tinted glass, attached
metal parts, unprotected or leaky caps, partially filled bottles, or other conditions permitting
contamination of milk or detracting from the appearance of the package.

52

EXPLANATION OF EXERCISE XVII

The main purpose of a bottle filler is to fill several bottles at the
same time and to do it in such a manner that there will be the smallest
possible amount of loss. With the modern filler the overflow, air,
froth, etc., is removed from the bottle by means of a small tube which
connects with the filler tube and extends upward above the level of the
milk in the filler tank. In cleaning the machine it is necesslary to
scrub the inside of these tubes with a long handled brush provided for
the purpose. Simply rinsing the tube is not sufficient. The filler
tubes usually consist of two parts, one which fits over the other, and
the outside tube works up and down on the inside tube when the filler
is operated. This makes it necessary for the tubes to fit perfectly,
and great care must be taken not to oughen the surfaces of these
tubes. In some cases the outside and inside tubes are numbered to
correspond so that the operator in assembling the machine may
always know which tubes fit one another.

The end of the outside filler tube is provided with a rubber gasket
so that a perfect union is made with the bottle when the filler is in
operation. Bottles with chipped and broken edges 'are liable to cut
the rubber gaskets, and unless pains are taken to clean them they
become filled with milk, rendering them unsanitary.

Bottles to be washed, should first be soaked in water as hot as the
hand will bear, to which has been added some washing powder. After
washing on the brushes, the bottles should be rinsed in a tank of clean,
hot water. The bottles should then be sterilized by means of live
steam. If live steam is not available they may be placed in scalding
hot water. It is best not to place the crates used to fill bottles inside
the sterilizer, as the action of live steam soon destroys the crates.
Crates suitable for this purpose may be made from ordinary lumber.
This method, however, has the disadvantage of making it necessary to
transfer the bottles to the filler crates at the time of bottling.

53

EXERCISE XVII
BOTTLING MILK AND WASHING BOTTLES

1. Place all loose parts of the filler in the filler tank and scald
them with hot water. Note whether the outside and inside filler
tubes are numbered and if they are, be sure to place together those
bearing the same number. Fill two cases of quart and one case of
pint bottles. Cap one case of quarts with the standard cap. Ice this
crate of bottles and set in the refrigerator. Fill one case of Dacro
bottles (small topped) and cap them.

2. Remove the old milk from the refrigerator and pour the milk
into a can. Also empty all bottles of milk not iced, and draw off into
a can all milk in the fillers. Wash the fillers, using small brushes for
the tubes. Collect all dirty bottles and wash them. Wash the
Dacro bottles with the foot power washer. Place the washed bottles
in the sterilizer and turn on the steam before leaving.

54
STUDENT'S NOTES AND REPORT

55

EXPLANATION OF EXERCISE XVIII

The clarification of milk consists in removing from it the insoluble
dirt. The modern clarifier does this by means of centrifugal force.
The dirt found in milk is usually heavier than the milk itself and the
action of the centrifugal force deposits this dirt on the inside of the
bowl. Clarifiers work on much the same principle as do separators,
but each make of machine has special features tending to prevent
separation. Usually a clarifier runs slower than does a separator of
the same make and capacity. In a separator, the inner device is so
constructed as to spread the milk in a thin layer, thereby making it
possible to do more complete separation.

In a clarifier the milk is not separated in as thin a layer and only
one outlet to the bowl is provided.

The different construction of each machine will be studied when
the machine is used.

EXERCISE XVIII
EFFECT OF TEMPERATURE ON CLARIFICATION

1. Weigh out two cans of milk and thoroughly mix them by
pouring from one can to another until they are of uniform composi-
tion.

2 . Clarify one can of milk at a temperature of 60° F. and clarify
the other at a temperature of 85° F. Note if there is any difference
in the kind and amount of sediment obtained.

3. Stain some of the sediment obtained from each clarification
and make a drawing of the field. In case there is no microscopical
difference in the sediment only one drawing need be made.

56
STUDENT'S NOTES AND REPORT

57

EXERCISE XIX

1. For use with the clarifier, weigh a can of milk and have the
temperature as near 60° F. as possible. Measure out 100 cc. of the
milk into a measuring cylinder, both before and after clarification.
Set these two cylinders aside and the next day compare the cream line
on the two samples. Also note if there is any sediment in the bottom
of either cylinder, and if so compare the amount.

2. Run the milk through the clarifier and keep track of the time
required for the process. Note the kind and amount of sediment
on the inside of the bowl.

3. Stain some of the sediment on a glass slide and examine it
under the high power microscope. Make a drawing of the field.

4. Reclarify the same amount of milk and compare the amount
and kind of sediment with that obtained in the first clarification.

5. Make a drawing showing the difference between the inner
device in a separator and a clarifier of the same make.

58
STUDENT'S NOTES AND REPORT

59

EXPLANATION OF EXERCISE XX

In sanitary milk production it must be kept constantly in mind
that clean milk means a product reasonably free from germ life. It
is not as difficult to keep germs out of milk as is commonly supposed.
There are a few simple and inexpensive practices which if carefully
followed will do much in aiding the dairyman to produce a good
product.

It is the purpose of the following experiments to illustrate the value
of certain dairy practices in clean milk production and the harmful
effects of certain other practices in producing clean milk.

In performing these experiments it must be borne in mind that
anything which prevents the entrance of dust and dirt into milk
is an aid to clean milk production. On the other hand, any disturb-
ance which causes dust particles to float around in the air makes it
easily possible for these particles to enter the milk while it is being
drawn and so contaminate it.

The use of the small top pail, and wiping the udder with a damp
cloth just before milking, are two things which are easy to do and are
comparatively inexpensive. At the same time, they are exceedingly
helpful in keeping germs out of milk.

On the other hand, the practice of feeding hay or grain just before
milking stirs up a dust and therefore makes it possible for a larger
number of micro-organisms to enter the milk.

EXERCISE XX
THE VALUE OF THE SMALL TOP PAIL IN CLEAN MILK PRODUCTION

1 . Carefully sterilize an ordinary wide top milk pail and a small
top or covered milk pail.

2. Select two cows standing near one another and whose flanks
and udders are alike as regards the amount of visible dirt on them.
Milk one cow in the wide mouth pail and the other cow in the small
top or covered pail.

3. Take a sample of milk in a sterile bottle from each pail and
plate the samples for bacteria. If it is necessary to hold the samples
for any length of time before plating, the bottle should be set on ice.

4. After the colonies in the plates have developed, note if there
is any difference in bacterial content of the milk drawn in the wide
mouth pail and that drawn in the small top or covered pail.

6o
STUDENT'S NOTES AND REPORT

6i
EXERCISE XXI

1 . Carefully sterilize two small top or covered pails.

2. Select two cows standing near one another whose udders and
flanks are alike so far as amount of visible dirt is concerned.

3 . Dampen with a cloth the udder and flanks of one of the cows
and milk her.

4. Milk the other cow without dampening the flank and udder.
5r In a sterile bottle, take a sample of milk from each milking and

plate the milk for bacteria. If the milk cannot be plated at once, the
bottle should be kept on ice. Compare the number of bacteria found
in the milk drawn under the two different conditions.

62

STUDENT'S NOTES AND REPORT

63

EXERCISE XXII

EFFECT OF FEEDING HAY, JUST BEFORE MILKING, ON THE GERM
CONTENT OF MILK

1 . Sterilize two small top pails and select two cows whose udders
and flanks are alike as regards the amount of visible dirt on them.

2 . Milk one of the cows and take in a sterile bottle a sample of the
milk for plating.

3. Before milking the second cow, shake two or three forkfuls of
hay near where she stands. Milk the cow and take in a sterile bottle
a sample of the milk for plating.

4. Compare the number of bacteria found in the milk drawn
before and after the hay was shaken.

64
STUDENT'S NOTES AND REPORT

INDEX

Bottle fillers 52

Bottling milk 53

Bottle washing 53

Clarification of milk 55,57

Clarifier 55

Cooling Milk 21,25

in cans 21

with brine and ice 26,27

with conical cooler 23

Dairy Utensils : 6

Cleaning of 5

Construction of 6

Damp Cloth 59, 61

Use in clean milk production 61

Dust 59

Effect of in clean milk production 59

Milk

Bottling 53

Clean 5

Cooling of milk . 21,25

Judging of 45, 46, 47

Standardizing 8,13

Pasteurization 16

Flash method 19

Holder method 17

Salt 26

Use of in cooling milk 26, 27

Score Card 31

for city milk plants 41

for cream 49

for Eairy building 32

for milk 45

Small top pail 59

Efficiency of 59

Standardization 8,13

Temperature 21

of milk for clarification 55

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