• TABLE OF CONTENTS
HIDE
 Front Cover
 Front Matter
 Table of Contents
 Introduction
 Location, arrangement and size...
 Floor plan
 Equipping the laboratory
 The babcock test
 The babcock test for butterfat...
 Modifications for homogenized...
 Testing for butterfat in cream
 Testing for butterfat in skimm...
 The fucoma (gerber) test
 Fucoma test for butterfat in whole...
 Fucoma test for butterfat...
 Fucoma test for butterfat...
 Fucoma test for butterfat in ice...
 The Minnesota test for butterfat...
 Pennsylvania test for butterfat...
 Plate count for bacteria in...
 The direct microscopic count
 Total solids test
 Sediment test
 Sediment test for bottled milk
 The methylene blue reduction...
 Use of the lactometer
 The acidity test
 The chlorine test
 Testing chlorine rinse water
 Alkali test
 A.B.C.B. caustic test
 The phosphatase test. Sharer field...
 Efficiency of homogenization
 Miscellaneous supplies and...






Group Title: Bulletin - University of Florida Agricultural Experiment Station ; 449
Title: A laboratory program for the dairy plant
CITATION PAGE IMAGE ZOOMABLE PAGE TEXT
Full Citation
STANDARD VIEW MARC VIEW
Permanent Link: http://ufdc.ufl.edu/UF00026708/00001
 Material Information
Title: A laboratory program for the dairy plant
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 30 p. : plan ; 23 cm.
Language: English
Creator: Mull, L. E ( Leon Edmund ), 1913-
Fouts, E. L ( Everett Lincoln ), b. 1890
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1948
 Subjects
Subject: Dairy products -- Testing   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: by Leon E. Mull and E.L. Fouts.
General Note: Cover title.
Funding: This collection includes items related to Florida’s environments, ecosystems, and species. It includes the subcollections of Florida Cooperative Fish and Wildlife Research Unit project documents, the Florida Sea Grant technical series, the Florida Geological Survey series, the Howard T. Odum Center for Wetland technical reports, and other entities devoted to the study and preservation of Florida's natural resources.
 Record Information
Bibliographic ID: UF00026708
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925530
oclc - 18271797
notis - AEN6183

Table of Contents
    Front Cover
        Page 1
    Front Matter
        Page 2
        Page 3
    Table of Contents
        Page 4
    Introduction
        Page 5
    Location, arrangement and size of laboratory
        Page 5
    Floor plan
        Page 6
    Equipping the laboratory
        Page 6
        Page 7
    The babcock test
        Page 8
    The babcock test for butterfat in whole milk
        Page 8
    Modifications for homogenized milk
        Page 9
    Testing for butterfat in cream
        Page 9
    Testing for butterfat in skimmilk
        Page 10
    The fucoma (gerber) test
        Page 11
    Fucoma test for butterfat in whole milk
        Page 11
    Fucoma test for butterfat in cream
        Page 12
    Fucoma test for butterfat in skimmilk
        Page 12
    Fucoma test for butterfat in ice cream
        Page 13
    The Minnesota test for butterfat in ice cream
        Page 13
    Pennsylvania test for butterfat in chocolate milk
        Page 14
    Plate count for bacteria in milk
        Page 15
        Page 16
    The direct microscopic count
        Page 17
        Page 18
    Total solids test
        Page 19
    Sediment test
        Page 20
    Sediment test for bottled milk
        Page 20
    The methylene blue reduction test
        Page 21
    Use of the lactometer
        Page 21
        Page 22
    The acidity test
        Page 23
    The chlorine test
        Page 24
    Testing chlorine rinse water
        Page 25
    Alkali test
        Page 25
    A.B.C.B. caustic test
        Page 26
    The phosphatase test. Sharer field test
        Page 27
    Efficiency of homogenization
        Page 28
    Miscellaneous supplies and materials
        Page 29
        Page 30
Full Text



October, 1948


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
HAROLD MOWRY, Director
GAINESVILLE, FLORIDA





GEORGE K. DAVIS




A LABORATORY PROGRAM


FOR THE DAIRY PLANT

By LEON E. MULL and E. L. FOUTs
















Single copies free to Florida residents upon request to
AGRICULTURAL EXPERIMENT STATION
GAINESVILLE, FLORIDA


Bulletin 449










BOARD OF CONTROL

J. Thos. Gurney, Chairman, Orlando
N. B. Jordan, Quincy
Thos. W. Bryant, Lakeland
J. Henson Markham, Jacksonville
Hollis Rinehart, Miami
W. F. Powers, Secretary, Tallahassee


EXECUTIVE STAFF

J. Hillis Miller, Ph.D., President of the
University3
H. Harold Hume, D.Sc., Provost for Agr.'
Harold Mowry, M.S.A., Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.
J. Francis Cooper, M.S.A., Editor3
Clyde Beale, A.B.J., Associate Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager3
Geo. F. Baughman, M.A., Business Managers
Claranelle Alderman, Accountants


MAIN STATION, GAINESVILLE

AGRICULTURAL ENGINEERING
Frazier Rogers, M.S.A., Agr. Engineers
J. M. Johnson, B.S.A.E., Asso. Agr. Engineers
J. M. Myers, B.S., Asso. Agr. Engineer
R. E. Choate, B.S.A.E., Asst. Agr. Engineers
A. M. Pettis, B.S.A.E., Asst. Agr. Engineers 8

AGRONOMY
Fred H. Hull, Ph.D., Agronomist'
G. E. Ritchey, M.S., Agronomist2
G. B. Killinger, Ph.D., Agronomist3
H. C. Harris, Ph.D., Agronomists
R. W. Bledsoe, Ph.D., Agronomist
M. E. Paddick, Ph.D., Agronomist
S. C. Litzenberger, Ph.D., Associate
W. A. Carver, Ph.D., Associate
Fred A. Clark, B.S., Assistant

ANIMAL INDUSTRY
A. L. Shealy, D.V.M., An. Industrialist' 3
R. B. Becker, Ph.D., Dairy Husbandman3
E. L. Fouts, Ph.D., Dairy Technologist3
D. A. Sanders, D.V.M., Veterinarian
M. W. Emmel, IY.V.M. Veterinarian3
L. E. Swanson, D.V.M., Parasitologist
N. R. Mehrhof, M.Agr., Poultry Husb.3
G. K. Davis, Ph.D., Animal Nutritionists
R. S. Glasscock, Ph.D., An. Husbandman3
P. T. Dix Arnold, M.S.A., Asst. Dairy Hush.'
L. E. Mull, M.S., Asst. in Dairy Tech.
Katherine Boney, B.S., Asst. Chem.
J. C. Driggers, B.S.A., Asst. Poultry Husb.S
Glenn Van Ness, D.V.M., Asso. Poultry
Pathologist
S. John Folks, B.S.A., Asst. An. Husb.3
W. A. Krienke, M.S., Asso. in Dairy Mfs.3
S. P. Marshall, Ph.D., Asso. Dairy Husb.3
C. F. Simpson, D.V.M., Asso. Veterinarian
C. F. Winchester, Ph.D., Asso. Biochemists


ECONOMICS, AGRICULTURAL
C. V. Noble, Ph.D., Agri. Economist"
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
D. E. Alleger, M.S., Associate
D. L. Brooke, M.S.A., Associate
R. E. L. Greene, Ph.D., Agri. Economist
H. W. Little, M.S., Assistant

Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist
J. C. Townsend, Jr., B.S.A., Agr. Statisticians
J. B. Owens, B.S.A., Agr. Statistician2
J. F. Steffens, Jr., B.S.A., Agr. Statisticians

ECONOMICS, HOME
Ouida D. Abbott, Ph.D., Home Econ.'
R. B. French, Ph.D., Biochemist

ENTOMOLOGY
A. N. Tissot, Ph.D., Entomologist'
L. C. Kuitert, Ph.D., Assistant
H. E. Bratley, M.S.A., Assistant

HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist'
F. S. Jamison, Ph.D., Horticulturist"
H. M. Reed, B.S., Chem., Veg. Processing
Byron E. Janes, Ph.D., Asso. Hort.
R. A. Dennison, Ph.D., Asso. Hort.
R. K. Showalter, M.S., Asso. Hort.
Albert P. Lorz, Ph.D., Asso. Hort.
R. H. Sharpe, M.S., Asso. Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.
Victor F. Nettles, M.S.A., Asst. Hort.'
F. S. Lagasse, Ph.D., Asso. Hort.2
L. H. Halsey, B.S.A., Asst. Hort.
Forrest E. Myers, B.S.A., Asst. Hort.

PLANT PATHOLOGY
W. B. Tisdale, Ph.D., Plant Pathologist'1
Phares Decker, Ph.D., Asso. Plant Path.
Erdman West, M.S., Mycologist and Botanist
Howard N. Miller, Ph.D., Asso. Plant Path.
Lillian E. Arnold, M.S., Asst. Botanist

SOILS
F. B. Smith, Ph.D., Microbiologist'3
Gaylord M. Volk, Ph.D., Chemist
J. R. Henderson, M.S.A., Soil Technologists
J. R. Neller, Ph.D., Soils Chemist
Nathan Gammon, Jr., Ph.D., Soils Chemist
C. E. Bell, Ph.D., Associate Chemist
R. A. Carrigan, Ph.D., Asso. Biochemists
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, Ph.D., Asso. Microbiologists
R. E. Caldwell, M.S.A., Asst. Chemist3
J. B. Cromartie, B.S.A., Soil Surveyor
Ralph G. Leighty, B.S., Asso. Soil Surveyor
V. W. Cyzycki, B.S., Asst. Soil Surveyor
R. B. Forbes, M.S., Asst. Soils Chemist
W. L. Pritchett, M.S., Asst. Chemist
Jean Beem, B.S.A., Asst. Soil Surveyor

'Head of Department.
2In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
4 On leave.










BRANCH STATIONS

NORTH FLORIDA STATION, QUINCY
J. D. Warner, M.S., Vice-Director in Charge
R. R. Kincaid, Ph.D., Plant Pathologist
W. H. Chapman, M.S., Asso. Agron.
R. C. Bond, M.S.A., Asso. Agronomist
L. G. Thompson, Ph.D., Soils Chemist
Frank S. Baker, Jr., B.S., Asst. An. Hush.
Kelvin Dorward, M.S., Entomologist

Mobile Unit, Monticello
R. W. Wallace, B.S., Associate Agronomist

Mobile Unit, Marianna
R. W. Lipscomb, M.S., Associate Agronomist

Mobile Unit, Wewahitchka
J. B. White, B.S.A., Associate Agronomist

Mobile Unit DeFuniak Springs
R. L. Smith, M.S., Associate Agronomist

CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge
W. L. Thompson, B.S., Entomologist
J. T. Griffiths, Ph.D., Asso. Entomologist
R. F. Suit, Ph.D., Plant Pathologist
E. P. Ducharme, M.S., Plant Pathologist*
R. K. Voorhees, Ph.D., Asso. Horticulturist
C. R. Stearns, Jr., B.S.A., Asso. Chemist
James K. Colehour, M.S., Asst. Chemist
T. W. Young, Ph.D., Asso. Horticulturist
J. W. Sites, M.S.A., Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist
J. A. Granger, B.S.A., Asst. Horticulturist
H. J. Reitz, M.S., Asso. Horticulturist
Francine Fisher, M.S., Asst. Plant Path.
I. W. Wander, Ph.D., Soils Chemist
A. E. Willson, B.S.A., Asso. Biochemist
J. W. Kesterson, M.S., Asso. Chemist
R. N. Hendrickson, B.S., Asst. Chemist
E. H. Bitcover, M.A., Soils Chemist
L. C. Knorr, Ph.D., Asso. Histologist
Joe P. Barnett, B.S.A., Asst. Horticulturist
J. C. Bowers, B.S., Asst. Chemist
D. S. Prosser, Jr., B.S., Asst. Horticulturist
R. W. Olsen, B.S., Biochemist
F. W. Wenzel, Jr., Ph.D., Supervisory Chem.

EVERGLADES STATION, BELLE GLADE
R. V. Allison, Ph.D., Vice-Director in Charge
F. D. Stevens, B.S., Sugarcane Agronomist
Thomas Bregger, Ph.D., Sugarcane
Physiologist
J. W. Randolph, M.S., Agricultural Engineer
W. T. Forsee, Jr., Ph.D., Chemist
R. W. Kidder, M.S., Asso. Animal Husb.
T. C. Erwin, Assistant Chemist
Roy A. Bair, Ph.D., Agronomist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
E. H. Wolf, Ph.D., Asst. Horticulturist
W. H. Thames, M.S., Asst. Entomologist
J. C. Hoffman, M.S., Asso. Horticulturist


C. B. Savage, M.S.A., Asst. Horticulturist
D. L. Stoddard, Ph.D., Asso. Plant Path.


SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
U. O. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
Robt. A. Conover, Ph.D., Asso. Plant Path.
R. W. Harkness, Ph.D., Asst. Chemist
Milton Cobin, B.S., Asso. Horticulturist


W. CENT. FLA. STATION, BROOKSVILLE
William Jackson, B.S.A., Animal Husband-
man in Charge2


RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in Charge
E. M. Hodges, Ph.D., Associate Agronomist
D. W. Jones, B.S., Asst. Soil Technologist
H. J. Fulford, B.S.A. Asst. Animal Hush.


CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. W. Wilson, Sc.D., Entomologist
Ben F. Whitner, Jr., B.S.A., Asst. Hort.

WEST FLORIDA STATION, MILTON
H. W. Lundy, B.S.A., Associate Agronomist


FIELD STATIONS

Leesborg
G. K. Parris, Ph.D., Plant Path. in Charge

Plant City
A. N. Brooks, Ph.D., Plant Pathologist

Hastings
A. H. Eddins, Ph.D., Plant Path. in Charge
E. N. McCubbin, Ph.D., Horticulturist

Monticello
A. M. Phillips, B.S., Asso. Entomologist2

Bradenton
J. R. Beckenbach, Ph.D., Hort. in Charge
E. G. Kelsheimer, Ph.D., Entomologist
David G. Kelbert, Asso. Horticulturist
E. L. Spencer, Ph.D., Soils Chemist
Robert 0. Magie, Ph.D., Gladioli Hort.
J. M. Walter, Ph.D., Plant Pathologist
Donald S. Burgis, M.S.A., Asst. Hort.

Lakeland
Warren 0. Johnson, B.S., Meteorologist2

1 Head of Department.
2 In cooperation with U. S.
s Cooperative, other divisions, U. of F.
SOn leave.










CONTENTS

Page

INTRODUCTION .........................--..............----......... 5
LOCATION, ARRANGEMENT AND SIZE OF THE LABORATORY ............................ 5
FLOOR PLAN ...................... -----..... ----- -------------------- 6
EQUIPPING THE LABORATORY .....---....-..........-- --------- ---------. 6
THE BABCOCK TEST ...................... ---- ---------------------------- 8
THE BABCOCK TEST FOR BUTTERFAT IN WHOLE MILK ...................-.......----- 8
MODIFICATIONS FOR HOMOGENIZED MILK .......................---.-------...... 9
TESTING FOR BUTTERFAT IN CREAM ................--------------- ----------------- 9
TESTING FOR BUTTERFAT IN SKIMMILK ................---- ----------------------- 10
THE FUCOMA (GERBER) TEST .....................---------- ------------------ 11
FUCOMA TEST FOR BUTTERFAT IN WHOLE MILK ...........................---------------- 11
FUCOMA TEST FOR BUTTERFAT IN CREAM ............-.............-....------. ----. 12
FUCOMA TEST FOR BUTTERFAT IN SKIMMILK .........................................-- 12
FUCOMA TEST FOR BUTTERFAT IN ICE CREAM .................................-------.. 13
THE MINNESOTA TEST FOR BUTTERFAT IN ICE CREAM ...........................--------- 13
PENNSYLVANIA TEST FOR BUTTERFAT IN CHOCOLATE MILK .........-.............- 14
PLATE COUNT FOR BACTERIA IN MILK ........................... ....--------- ----------------- 15
THE DIRECT MICROSCOPIC COUNT .......................------------------- -------------- 17
THE TOTAL SOLIDS TEST ............................ ------- ---------------- 19
SEDIMENT TEST ................................ --.. -------- ---------- ------- 20
SEDIMENT TEST FOR BOTTLED MILK ............................ ..----...-- -- ---- 20
SEDIMENT TEST FOR MILK IN 10-GALLON CANS ................................----........ 20
THE METHYLENE BLUE REDUCTION TEST ........-............... .......-----------. 21
USE OF THIE LACTOMETER ................................----- --------- 21
THE ACIDITY TEST ...................--------------- ----- ----------- 23
THE CHLORINE TEST ....................................... .---- --. --------------- 24
TESTING CHLORINE RINSE W ATER .................................................. 25
TESTING CHLORINE STOCK SOLUTION ...........................-------. ------.... 25
ALKALI TEST ..........................................----....-----.... 25
A.B.C.B. CAUSTIC TEST ...................... .....................--------- 26
THE PHOSPHATASE TEST. SHARER FIELD TEST ................................----------- 27
EFFICIENCY OF HOMOGENIZATION ...............................---.. ......----- 28
MISCELLANEOUS SUPPLIES AND MATERIALS .............. ..-.................... --29










A LABORATORY PROGRAM FOR THE
DAIRY PLANT
By LEON E. MULL and E. L. FOUTS

Introduction
Every dairy plant in which milk and milk products are pro-
cessed should have a laboratory for the control of composition
and quality. For reasons of efficiency and economy, the labora-
tory must necessarily be adapted to the needs of each individual
plant. Such details as size, location, equipment, personnel and
chemical and bacteriological tests should receive careful atten-
tion. It is imperative, therefore, that the operator be familiar
with the requirements of a laboratory before attempting to es-
tablish one for his own dairy plant.
The purpose of this bulletin is to point out some of the neces-
sary requirements for planning, equipping and operating a dairy
plant laboratory with the thought that these suggestions may be
of assistance to those already operating laboratories and the
bulletin may serve as a guide to those who are contemplating es-
tablishing a laboratory.

Location, Arrangement and Size of the Laboratory
The location of the laboratory within the plant is important be-
cause of the nature of the work to be performed. Of primary
importance, convenience of operations must be considered first.
It should be placed nearby or adjacent to the scene of operations
which it will serve. Freedom from drafts, steam, vibrations
and noise is desirable. Not to be overlooked is the advertising
value of the milk plant laboratory. If possible, the laboratory
should be located and constructed in such manner that customers
and visitors entering and leaving the plant will be attracted at
once by the laboratory and its personnel at work. Ample win-
dow space is desirable.
The inside of the laboratory must be well lighted, well venti-
lated and scrupulously clean. Tile is excellent for flooring ma-
terial. Walls and ceiling should be smooth, light in color and
preferably white.
The amount of floor space allotted to the laboratory can be
governed by the size of the plant and the amount of work to be
done. It should be large enough to accommodate all of the










A LABORATORY PROGRAM FOR THE
DAIRY PLANT
By LEON E. MULL and E. L. FOUTS

Introduction
Every dairy plant in which milk and milk products are pro-
cessed should have a laboratory for the control of composition
and quality. For reasons of efficiency and economy, the labora-
tory must necessarily be adapted to the needs of each individual
plant. Such details as size, location, equipment, personnel and
chemical and bacteriological tests should receive careful atten-
tion. It is imperative, therefore, that the operator be familiar
with the requirements of a laboratory before attempting to es-
tablish one for his own dairy plant.
The purpose of this bulletin is to point out some of the neces-
sary requirements for planning, equipping and operating a dairy
plant laboratory with the thought that these suggestions may be
of assistance to those already operating laboratories and the
bulletin may serve as a guide to those who are contemplating es-
tablishing a laboratory.

Location, Arrangement and Size of the Laboratory
The location of the laboratory within the plant is important be-
cause of the nature of the work to be performed. Of primary
importance, convenience of operations must be considered first.
It should be placed nearby or adjacent to the scene of operations
which it will serve. Freedom from drafts, steam, vibrations
and noise is desirable. Not to be overlooked is the advertising
value of the milk plant laboratory. If possible, the laboratory
should be located and constructed in such manner that customers
and visitors entering and leaving the plant will be attracted at
once by the laboratory and its personnel at work. Ample win-
dow space is desirable.
The inside of the laboratory must be well lighted, well venti-
lated and scrupulously clean. Tile is excellent for flooring ma-
terial. Walls and ceiling should be smooth, light in color and
preferably white.
The amount of floor space allotted to the laboratory can be
governed by the size of the plant and the amount of work to be
done. It should be large enough to accommodate all of the







Florida Agricultural Experiment Station


equipment and fixtures, provide ample space for the laboratory
personnel to perform their duties and allow for any additional
functions which might be assigned to the laboratory if the or-
ganization expands operations.

Floor Plan
Figure 1 shows a floor plan designed to meet the minimum re-
quirements of a large dairy plant. It will be noted on the plan
that the laboratory is divided into two sections-the bacteriolog-
ical section and the chemical section. While this arrangement has
many desirable features, it may be advantageous in some in-
stances to combine the two into a somewhat smaller one-room
laboratory.
As an added suggestion it is well to consider additional storage
space to. relieve the storage problem in the laboratory proper.
Adjoining the laboratory a small rectangular room 8 feet long
and 5 feet wide and of the same height as the laboratory will
accommodate such laboratory equipment as is not in daily use, as
well as a fairly large inventory of laboratory supplies. Built-in
shelves extending from the floor to the ceiling are satisfactory
for the storage room.

Equipping the Laboratory
The specific tests and the number of samples of each test to
be conducted will govern to a certain extent the kind and amount
of equipment required. The following tests are suggested as the
average requirements for a large plant.
The following tests are outlined briefly, stating the purpose of
each, the principle involved and the minimum quantity of ma-
terials required. In most instances additional materials will be
needed depending upon the number of tests to be run.

1. Butterfat test. Babcock or Fucoma, optional.
2. Bacteriological plate count.
3. Direct microscopic count.
4. Total solids test.
5. Sediment test.
6. Methylene blue test.
7. Lactometer test.
8. Acidity test.
9. Chlorine test.
10. Alkali test.
11. Phosphatase test.
12. Efficiency of homogenization.







Florida Agricultural Experiment Station


equipment and fixtures, provide ample space for the laboratory
personnel to perform their duties and allow for any additional
functions which might be assigned to the laboratory if the or-
ganization expands operations.

Floor Plan
Figure 1 shows a floor plan designed to meet the minimum re-
quirements of a large dairy plant. It will be noted on the plan
that the laboratory is divided into two sections-the bacteriolog-
ical section and the chemical section. While this arrangement has
many desirable features, it may be advantageous in some in-
stances to combine the two into a somewhat smaller one-room
laboratory.
As an added suggestion it is well to consider additional storage
space to. relieve the storage problem in the laboratory proper.
Adjoining the laboratory a small rectangular room 8 feet long
and 5 feet wide and of the same height as the laboratory will
accommodate such laboratory equipment as is not in daily use, as
well as a fairly large inventory of laboratory supplies. Built-in
shelves extending from the floor to the ceiling are satisfactory
for the storage room.

Equipping the Laboratory
The specific tests and the number of samples of each test to
be conducted will govern to a certain extent the kind and amount
of equipment required. The following tests are suggested as the
average requirements for a large plant.
The following tests are outlined briefly, stating the purpose of
each, the principle involved and the minimum quantity of ma-
terials required. In most instances additional materials will be
needed depending upon the number of tests to be run.

1. Butterfat test. Babcock or Fucoma, optional.
2. Bacteriological plate count.
3. Direct microscopic count.
4. Total solids test.
5. Sediment test.
6. Methylene blue test.
7. Lactometer test.
8. Acidity test.
9. Chlorine test.
10. Alkali test.
11. Phosphatase test.
12. Efficiency of homogenization.











12'-0"


UIC(LLAHEO1/ CIIMI(MLMTEI THUL6
(Wiul ORAWERM f CABIMEr)


LAB SIOOL
O


-(uIMICkL
- L bO NA TON.rY"


LAS STO0I1
0


LAD 5TOOU.0


Fig. 1.-Floor plan for a dairy plant laboratory.


-I;LTLIIL=I=2~







Florida Agricultural Experiment Station


The Babcock Test
Purpose
To determine the percentage of butterfat in dairy products.
Principle
Strong commercial sulfuric acid dissolves the solids-not-fat
and produces heat that aids in coalescing the fat globules. A
centrifuge is used to separate the fat completely from the acid
mixture, which has a higher specific gravity than the fat. Spe-
cial glassware makes it possible to read the percentage of fat
directly from the bottle.

The Babcock Test for Butterfat in Whole Milk
Materials Required
Babcock centrifuge
Babcock milk test bottles (18-gram, 8 or 10%)
Commercial sulfuric acid (sp. gr. 1.82-1.83)
17.6 ml. pipette
17.5 ml. acid measure
Floating thermometer with Fahrenheit scale
Water bath
Dividers for reading test.

Procedure
1. Temper the sample of milk to be tested to 60-700 F. and
mix thoroughly by pouring several times from one container to
another.
2. Transfer 17.5 ml. of the milk to an 8 percent or 10 percent
milk test bottle. Blow the last drop of milk from the pipette in-
to the bottle.
3. Add 17.5 ml. of sulfuric acid, previously tempered to 60-700
F., to the test bottle. Hold the test bottle at a 45 degree angle
and rotate while pouring the acid, so that any milk adhering to
the neck of the bottle will be washed into the bulb of the test
bottle.
4. Rotate the milk-acid mixture in the test bottle until a uni-
form reddish-brown color is obtained.
5. Place the bottle in centrifuge (centrifuge must be balanced)
and whirl at the proper speed for five minutes.
6. Add enough soft or distilled water at 130-1400 F. to bring
the liquid level to the 0 mark in the bottle neck.
7. Return the bottles to the centrifuge and whirl for two min-
utes.







Florida Agricultural Experiment Station


The Babcock Test
Purpose
To determine the percentage of butterfat in dairy products.
Principle
Strong commercial sulfuric acid dissolves the solids-not-fat
and produces heat that aids in coalescing the fat globules. A
centrifuge is used to separate the fat completely from the acid
mixture, which has a higher specific gravity than the fat. Spe-
cial glassware makes it possible to read the percentage of fat
directly from the bottle.

The Babcock Test for Butterfat in Whole Milk
Materials Required
Babcock centrifuge
Babcock milk test bottles (18-gram, 8 or 10%)
Commercial sulfuric acid (sp. gr. 1.82-1.83)
17.6 ml. pipette
17.5 ml. acid measure
Floating thermometer with Fahrenheit scale
Water bath
Dividers for reading test.

Procedure
1. Temper the sample of milk to be tested to 60-700 F. and
mix thoroughly by pouring several times from one container to
another.
2. Transfer 17.5 ml. of the milk to an 8 percent or 10 percent
milk test bottle. Blow the last drop of milk from the pipette in-
to the bottle.
3. Add 17.5 ml. of sulfuric acid, previously tempered to 60-700
F., to the test bottle. Hold the test bottle at a 45 degree angle
and rotate while pouring the acid, so that any milk adhering to
the neck of the bottle will be washed into the bulb of the test
bottle.
4. Rotate the milk-acid mixture in the test bottle until a uni-
form reddish-brown color is obtained.
5. Place the bottle in centrifuge (centrifuge must be balanced)
and whirl at the proper speed for five minutes.
6. Add enough soft or distilled water at 130-1400 F. to bring
the liquid level to the 0 mark in the bottle neck.
7. Return the bottles to the centrifuge and whirl for two min-
utes.








A Laboratory Program for the Dairy Plant


8. Add enough soft or distilled water at 130-1400 F. to bring
the liquid level to the 6 or 7 percent graduation on the bottle
neck.
9. Return the bottle to the centrifuge and whirl for one min-
ute.
10. Transfer the bottles to a water bath, maintained at 130-
1400 F., for five- minutes. The water level in the water bath
should be slightly higher than the level of the fat columns in the
test bottle necks.
11. Read the percentage butterfat in each bottle immediately
after removing the bottle from the hot water bath.
12. By using the dividers, the percentage butterfat may be
measured as follows: Place one point of the dividers at the ex-
treme bottom of the fat column and the other point at the ex-
treme top of the upper curved surface. Without changing the
spread of the dividers, place one point on the zero mark of the
graduations and the other point then indicates the percentage of
fat in the milk.

Modifications for Homogenized Milk
1. Temper acid and milk to 700 F.
2. Use the full amount of acid (17.5 ml.).
3. Add the acid in three portions, 8, 5, and 4.5 ml.
4. Mix the acid and milk by rotary motion after each addition
and continue agitation for at least 15 seconds before adding the
second and third increments of sulfuric acid.
5. Shake the tests for at least two minutes before centrifug-
ing.
6. Centrifuge and add hot water in accordance with the regu-
lar Babcock procedure. Substitution of a water-alcohol (ratio
1.4:1 by weight) solution for the hot water to bring the fat up
into the neck of the bottle for reading is optional.
7. Complete the test in the usual manner.

Testing for Butterfat in Cream
Materials Required
Babcock centrifuge
Babcock cream test bottles (50 percent, 9-gram, 6-inch bottle)
Commercial sulfuric acid (1.82-1.83 specific gravity)
9 ml. pipette
9 ml. acid measure
Floating dairy thermometer with Fahrenheit scale
Water bath








A Laboratory Program for the Dairy Plant


8. Add enough soft or distilled water at 130-1400 F. to bring
the liquid level to the 6 or 7 percent graduation on the bottle
neck.
9. Return the bottle to the centrifuge and whirl for one min-
ute.
10. Transfer the bottles to a water bath, maintained at 130-
1400 F., for five- minutes. The water level in the water bath
should be slightly higher than the level of the fat columns in the
test bottle necks.
11. Read the percentage butterfat in each bottle immediately
after removing the bottle from the hot water bath.
12. By using the dividers, the percentage butterfat may be
measured as follows: Place one point of the dividers at the ex-
treme bottom of the fat column and the other point at the ex-
treme top of the upper curved surface. Without changing the
spread of the dividers, place one point on the zero mark of the
graduations and the other point then indicates the percentage of
fat in the milk.

Modifications for Homogenized Milk
1. Temper acid and milk to 700 F.
2. Use the full amount of acid (17.5 ml.).
3. Add the acid in three portions, 8, 5, and 4.5 ml.
4. Mix the acid and milk by rotary motion after each addition
and continue agitation for at least 15 seconds before adding the
second and third increments of sulfuric acid.
5. Shake the tests for at least two minutes before centrifug-
ing.
6. Centrifuge and add hot water in accordance with the regu-
lar Babcock procedure. Substitution of a water-alcohol (ratio
1.4:1 by weight) solution for the hot water to bring the fat up
into the neck of the bottle for reading is optional.
7. Complete the test in the usual manner.

Testing for Butterfat in Cream
Materials Required
Babcock centrifuge
Babcock cream test bottles (50 percent, 9-gram, 6-inch bottle)
Commercial sulfuric acid (1.82-1.83 specific gravity)
9 ml. pipette
9 ml. acid measure
Floating dairy thermometer with Fahrenheit scale
Water bath








Florida Agricultural Experiment Station


Torsion cream balance with 9-gram weight
Glymol (red-reader)
Dividers for reading test.
Procedure
1. Temper the sample of cream to be tested to 90-1100 F. and
mix thoroughly by pouring several times from one container to
another.
2. Balance two cream test bottles on opposite pans of the bal-
ance and weigh exactly 9 grams of cream into each of the
bottles.
3. Add acid in small amounts, usually about 9 ml., mixing well
with the cream after each addition until the characteristic coffee-
brown color appears.
4. Add 5 ml. of soft warm water to the cream-acid mixture to
retard the action of the acid.
5. The remainder of the procedure is the same as for milk,
except that 4 or 5 drops of glymol, also referred to as "red read-
er," are allowed to run down the neck of the test bottle and to
rest on top of the fat column. The fat column is read by plac-
ing one point of the dividers at the extreme lower end of the col-
umn and the other point at the glymol-fat junction. Without
changing the spread of the dividers, place one point on the zero
mark of the graduation and the other point indicates the per-
centage of'fat in the cream.

Testing for Butterfat in Skimmilk
Materials Required
Babcock centrifuge
Babcock double-neck skimmilk test bottles
Commercial sulfuric acid (sp. gr. 1.82-1.83)
17.6 ml. pipette
17.5 ml. acid measure
Floating dairy thermometer with Fahrenheit scale
Water bath.
Procedure
1. Temper sample to 60-70o F. and mix thoroughly by pouring
several times from one container to another.
2 With the pipette, transfer 17.5 ml. to a skimmilk test bottle.
3. Temper acid to 60-700 F. and add a total of from 18 to 20
ml. in approximately three equal portions, thoroughly mixing
each portion with the skimmilk.
4. Centrifuge at the proper speed for 10, two and one minutes,








A Laboratory Program for the Dairy Plant


making the usual fillings with hot water as described under test-
ing whole milk.
5. Transfer the bottles to a water bath maintained at 130-
1400 F. for five minutes.
6. Read the percentage butterfat in each bottle immediately
after removing the bottle from the hot water bath, by the use of
the dividers or by reading directly from the graduated portion
of the neck.

The Fucoma (Gerber) Test
Purpose
To determine the percentage of butterfat in dairy products.

Principle
Sulfuric acid serves three purposes:
1. Dissolves solids-not-fat.
2. Liberates the fat.
3. Creates heat to keep fat in liquid condition.
Amyl alcohol prevents charring of the fat and enables a clear
reading of the fat column.

Fucoma Test for Butterfat in Whole Milk
Materials Required
Fucoma centrifuge
Milk butyrometers (8 or 10 percent) with stoppers
Milk butyrometer stopper keys
Automatic measure for acid (10 ml.)
Automatic measure for amyl alcohol (1 ml.)
11 ml. pipette for milk
Filling and shaking stand
Water bath
Commercial sulfuric acid (sp. gr. 1.82-1.83)
Amyl alcohol special for Fucoma test
Floating dairy thermometer.

Procedure
1. Transfer 10 ml. sulfuric acid to butyrometer.
2. Mix sample thoroughly by pouring from one vessel to an-
other.
3. Measure into test bottle 11 ml. of milk.
4. Add 1 ml. of amyl alcohol.
5. Insert stopper into bottle and mix thoroughly by inverting
the butyrometer several times until the curd is dissolved.
6. Place the butyrometer into the centrifuge with the neck








A Laboratory Program for the Dairy Plant


making the usual fillings with hot water as described under test-
ing whole milk.
5. Transfer the bottles to a water bath maintained at 130-
1400 F. for five minutes.
6. Read the percentage butterfat in each bottle immediately
after removing the bottle from the hot water bath, by the use of
the dividers or by reading directly from the graduated portion
of the neck.

The Fucoma (Gerber) Test
Purpose
To determine the percentage of butterfat in dairy products.

Principle
Sulfuric acid serves three purposes:
1. Dissolves solids-not-fat.
2. Liberates the fat.
3. Creates heat to keep fat in liquid condition.
Amyl alcohol prevents charring of the fat and enables a clear
reading of the fat column.

Fucoma Test for Butterfat in Whole Milk
Materials Required
Fucoma centrifuge
Milk butyrometers (8 or 10 percent) with stoppers
Milk butyrometer stopper keys
Automatic measure for acid (10 ml.)
Automatic measure for amyl alcohol (1 ml.)
11 ml. pipette for milk
Filling and shaking stand
Water bath
Commercial sulfuric acid (sp. gr. 1.82-1.83)
Amyl alcohol special for Fucoma test
Floating dairy thermometer.

Procedure
1. Transfer 10 ml. sulfuric acid to butyrometer.
2. Mix sample thoroughly by pouring from one vessel to an-
other.
3. Measure into test bottle 11 ml. of milk.
4. Add 1 ml. of amyl alcohol.
5. Insert stopper into bottle and mix thoroughly by inverting
the butyrometer several times until the curd is dissolved.
6. Place the butyrometer into the centrifuge with the neck








Florida Agricultural Experiment Station


toward the center, making certain that the centrifuge is bal-
anced with an equal number of butyrometers placed directly op-
posite one another.
7. Centrifuge four minutes at 1,000 revolutions per minute.
8. Remove butyrometers from centrifuge, place in water bath
heated to 1400 F. for five minutes.
9. Take the reading from the bottom of the fat column to the
bottom of the meniscus, the curved portion at the top.

Fucoma Test for Butterfat in Cream
Materials Required
Fucoma centrifuge
Special cream butyrometers
Cream scales
5 ml. pipette
Automatic measure for acid
Automatic measure for amyl alcohol
Bottle rack
Water bath
Commercial sulfuric acid (sp. gr. 1.82-1.83)
Amyl alcohol, special for Fucoma test
Cream balance and 5-gram weight
Floating dairy thermometer.

Procedure
1. Transfer 10 ml. sulfuric acid to each test bottle.
2. Using special supports, balance each bottle on the cream
scales.
3. Weigh into each bottle exactly 5 grams of the well mixed
cream.
4. Add 5 ml. of water and 1 ml. of amyl alcohol.
5. Insert stopper and shake thoroughly.
6. Place bottles in centrifuge with stopper end toward outside.
Make sure the centrifuge is balanced.
7. Centrifuge five minutes at 1,000 r.p.m.
8. Place bottles in water bath for five minutes at 1400 F.
9. By releasing or increasing the pressure on the stopper,
bring the bottom of the meniscus (curved surface at top of liq-
quid fat) exactly to the 0 mark. The reading at the lower end
of the scale, which is a straight line, then gives the percent of
fat in the cream.

Fucoma Test for Butterfat in Skimmilk
Materials Required
Special skimmilk butyrometer
Other materials same as for testing whole milk.








Florida Agricultural Experiment Station


toward the center, making certain that the centrifuge is bal-
anced with an equal number of butyrometers placed directly op-
posite one another.
7. Centrifuge four minutes at 1,000 revolutions per minute.
8. Remove butyrometers from centrifuge, place in water bath
heated to 1400 F. for five minutes.
9. Take the reading from the bottom of the fat column to the
bottom of the meniscus, the curved portion at the top.

Fucoma Test for Butterfat in Cream
Materials Required
Fucoma centrifuge
Special cream butyrometers
Cream scales
5 ml. pipette
Automatic measure for acid
Automatic measure for amyl alcohol
Bottle rack
Water bath
Commercial sulfuric acid (sp. gr. 1.82-1.83)
Amyl alcohol, special for Fucoma test
Cream balance and 5-gram weight
Floating dairy thermometer.

Procedure
1. Transfer 10 ml. sulfuric acid to each test bottle.
2. Using special supports, balance each bottle on the cream
scales.
3. Weigh into each bottle exactly 5 grams of the well mixed
cream.
4. Add 5 ml. of water and 1 ml. of amyl alcohol.
5. Insert stopper and shake thoroughly.
6. Place bottles in centrifuge with stopper end toward outside.
Make sure the centrifuge is balanced.
7. Centrifuge five minutes at 1,000 r.p.m.
8. Place bottles in water bath for five minutes at 1400 F.
9. By releasing or increasing the pressure on the stopper,
bring the bottom of the meniscus (curved surface at top of liq-
quid fat) exactly to the 0 mark. The reading at the lower end
of the scale, which is a straight line, then gives the percent of
fat in the cream.

Fucoma Test for Butterfat in Skimmilk
Materials Required
Special skimmilk butyrometer
Other materials same as for testing whole milk.








A Laboratory Program for the Dairy Plant


Procedure
1. The same as for testing milk except centrifuging, which
is carried on for 10 to 15 minutes.

Fucoma Test for Butterfat in Ice Cream
NOTE: Ice cream contains so high a percentage of sugar that
charring often results. This difficulty is largely overcome by
the use of dilute sulfuric acid and amyl alcohol.

Materials Required
1. The same as for cream test with these exceptions:
a. Special ice cream butyrometers.
b. Dilute sulfuric acid made by mixing the regular commercial
acid (sp. gr. 1.82-1.83) with water as follows:
For mix and all flavors except chocolate take 13 ml. of water and
slowly add 87 ml. of acid.
For chocolate ice cream take 6 ml. of water and add slowly 94
ml. of acid.
CAUTION: Always add acid to water.

Procedure
1. Transfer 10 ml. acid to test bottle.
2. Melt sample. Weigh 5 grams of well mixed sample into a
special ice cream test bottle on top of acid.
3. Add 5 ml. of water and 1 ml. of amyl alcohol.
4. Insert stopper. Shake, centrifuge five minutes, temper at
1400 F. for five minutes and make readings as for milk.

The Minnesota Test for Butterfat in Ice Cream
Purpose
To determine the percentage of butterfat in ice cream.

Principle
Alkaline reagents and heat dissolve solids not fat and maintain
the fat in a liquid condition. Alcohol helps prevent charring of
sugar. Centrifugal force separates and collects fat into neck of
test bottle.

Materials Required
Minnesota reagent prepared by Kimble Glass Company (Kimble-Nafis,
Dairy Division, Vineland, New Jersey)
20 percent 9-gram ice cream test bottles
Babcock centrifuge
9 ml. pipette
Water bath for boiling water








A Laboratory Program for the Dairy Plant


Procedure
1. The same as for testing milk except centrifuging, which
is carried on for 10 to 15 minutes.

Fucoma Test for Butterfat in Ice Cream
NOTE: Ice cream contains so high a percentage of sugar that
charring often results. This difficulty is largely overcome by
the use of dilute sulfuric acid and amyl alcohol.

Materials Required
1. The same as for cream test with these exceptions:
a. Special ice cream butyrometers.
b. Dilute sulfuric acid made by mixing the regular commercial
acid (sp. gr. 1.82-1.83) with water as follows:
For mix and all flavors except chocolate take 13 ml. of water and
slowly add 87 ml. of acid.
For chocolate ice cream take 6 ml. of water and add slowly 94
ml. of acid.
CAUTION: Always add acid to water.

Procedure
1. Transfer 10 ml. acid to test bottle.
2. Melt sample. Weigh 5 grams of well mixed sample into a
special ice cream test bottle on top of acid.
3. Add 5 ml. of water and 1 ml. of amyl alcohol.
4. Insert stopper. Shake, centrifuge five minutes, temper at
1400 F. for five minutes and make readings as for milk.

The Minnesota Test for Butterfat in Ice Cream
Purpose
To determine the percentage of butterfat in ice cream.

Principle
Alkaline reagents and heat dissolve solids not fat and maintain
the fat in a liquid condition. Alcohol helps prevent charring of
sugar. Centrifugal force separates and collects fat into neck of
test bottle.

Materials Required
Minnesota reagent prepared by Kimble Glass Company (Kimble-Nafis,
Dairy Division, Vineland, New Jersey)
20 percent 9-gram ice cream test bottles
Babcock centrifuge
9 ml. pipette
Water bath for boiling water








Florida Agricultural Experiment Station


Water bath for tempering at 135 F.
Cream balance and 9-gram weight
Dividers.
Procedure
1. Weigh 9 grams of the well mixed sample into the ice cream
test bottle.
2. Measure into the test bottle 15 ml. of the Minnesota
reagent. Shake thoroughly and place in a water bath at 1800
F. to boiling until fat appears in a clear layer at the top. Shake
once or twice during the digestion period (10-15 minutes).
3. Centrifuge 1/2 minute.
4. Fill the bottle with hot water to bring fat up into graduated
portion.
5. Centrifuge 1/2 minute.
6. Temper in water bath at 1350 F. for five minutes.
7. Add 2 or 3 drops of glymol to the test bottle.
8. Read test.

Pennsylvania Test for Butterfat in Chocolate Milk
Purpose

To determine percentage of butterfat in chocolate milk.

Principle
Same as Babcock test for milk, except that modifications are
made to prevent charring.

Materials Required
Babcock tester
Cream balance
18-gram weight
8 or 10 percent milk test bottles
Water bath
Glymol
Dividers
Burettes calibrated to 0.1 ml.
The following solutions:
(a) Ammonium hydroxide (28-29 percent NH )
(b) Butyl alcohol
(c) Dilute sulfuric acid; made by adding 809 ml. of commercial
sulfuric acid (sp. gr. 1.83) to 191 ml. of water. This will re-
duce the sp. gr. to about 1.73 as desired. Cool the mixture prior
to use and make further adjustments if necessary to secure a
specific gravity of 1.73 in the diluted acid.
Procedure
1. Mix the chocolate milk thoroughly.
2. Weigh 18 grams of sample into milk test bottle.







A Laboratory Program for the Dairy Plant


3. Add 1 ml. of ammonium hydroxide and mix.
4. Add 4 ml. of butyl alcohol and mix.
5. Add 17.5 ml. of dilute sulfuric acid and mix thoroughly.
6. Centrifuge for five minutes in a Babcock tester and add hot
water to bring fat to base of neck.
NOTE: Do not mix contents of bottle at this stage, as it will
drastically lower the fat reading.
7. Centrifuge for two minutes and add hot water to bring fat
into neck of bottle.
8. Centrifuge one minute.
9. Set bottles in water bath at 135 to 1400 F. for five minutes.
10. Add glymol to top of fat column. Allow to stand one to
two minutes and take reading from bottom of fat column to line
of demarcation between glymol and fat.
CAUTIONS: 1. Add ammonia and butyl alcohol to test bottle
from a burette.
2. In preparing dilute sulfuric acid, add acid to water. Never
add water to acid.

Plate Count for Bacteria in Milk
Purpose
To determine the numbers of bacteria in milk.

Principle
A known dilution of the milk sample is made, using sterile
water. This is plated on special bacteriological media. Each
bacterium is presumed to reproduce rapidly enough when incu-
bated at 950 F. for 48 hours to form a colony which can be
readily noted without magnification. The number of colonies
per plate multiplied by the dilution represents the number of
bacteria present in the milk.

Materials Required
Autoclave
Hot air sterilizer
Bacteriological incubator
Cream balance and weights
Bacterial plate counter
Metal pipette boxes
Metal bacterial plate boxes
Electric heater, hot plate or gas stove
Alcohol or gas burner
Test tube baskets
Double boiler
Absorbent cotton
Non-absorbent cotton







Florida Agricultural Experiment Station


Rubber tubing
China marking pencil
Glassware
3 floating dairy thermometers
1 Centigrade thermometer (-10* to 100* C.)
1 Centigrade thermometer (00 to 2500 C.)
2 6-inch funnels
1 gross petri dishes 100 mm. diameter x 15 mm. high
1 100-ml. graduated cylinder
1 500-ml. graduated cylinder
1 1,000-ml. graduated cylinder
1 gross 1.0 to 1.1-ml. bacteriological pipettes
1 10-ml. pipette
1 25-ml. pipette
1 gross 6-oz. Pyrex dilution bottles
1 gross Escher type rubber stoppers for dilution bottles
1 gross Pyrex test tubes, 6-inch length x 5/-inch diameter.
Procedure
1. Preparation of Medium.-Dehydrated tryptone glucose
extract agar may be purchased from many chemical and labora-
tory equipment firms with complete instructions for use. Pre-
pare the agar according to manufacturer's recommendations,
then tube the hot medium in as nearly 10-ml. quantities as pos-
sible in test tubes. Plug test tubes with cotton and sterilize in
an autoclave at 15 pounds pressure for 20 minutes. Remove
from autoclave as soon as pressure recedes to 0. When cool, store
in a cool place.
2. Preparation of Dilution Blanks.-The dilution blanks should
contain 99 ml. of water when ready for use. It is necessary to
add about 2 ml. of water more than the required amount to al-
low for slight evaporation during sterilization. After adding
101 ml. of water to each bottle, place the stoppers in loosely.
Sterilize in an autoclave at 15 pounds pressure for 20 minutes.
Allow pressure to recede gradually and then quickly press rubber
stoppers tightly in bottles. Store water blanks in a cool place
until ready for use.
3. Preparation of Glassware.-Place 1.0 to 1.1-ml. pipettes in
special metal sterilizing containers. Place the metal containers
in a hot-air sterilizer and raise the temperature to not less than
1700 C. (338 F.). Maintain temperature at not less than 1700
C. for at least one hour.
4. Preparing the Plates and Making the Count.-Mix sample
of milk thoroughly by inverting original container several times.
Remove stopper and transfer 1 ml. of sample with sterile pipette
to the sterile 99 ml. water blank, blowing out the last drop. Re-
place stopper and shake sample 25 times with an up and down







A Laboratory Program for the Dairy Plant


motion for seven seconds. This makes a 1 to 100 dilution. To
prepare a 1 to 1,000 dilution, remove 11 ml. from the 1 to 100 di-
lution with a fresh sterile pipette and transfer it to another 99
ml. water blank. Replace stopper and shake as above. To pre-
pare a 1 to 10 dilution add 11 ml. of milk to a 99 ml. water blank.
When proper dilutions have been made and properly mixed,
transfer 1 ml. of each dilution to its respective sterilized petri
dish, marking the dish to indicate the dilution. A fresh sterile
pipette must be used for each transfer. Close cover of petri
dish quickly after making transfer.
Before pouring the medium, the 10-ml. tubes of agar medium
must be melted in boiling water. When completely melted, tem-
per them to 104 to 1130 F. or 40 to 450 C. by placing them in
water within this range. Using one tube for each petri dish, re-
move the cotton plug, tilt the cover to petri dish just enough to
admit one end of tube and pour contents into dish. Replace
cover; tilt the dish from side to side to permit the mixture to
flow uniformly over the entire bottom surface.
Allow the petri dishes to stand undisturbed until the agar-
dilution mixture hardens. When agar has hardened, invert
petri dishes and place in an incubator. Incubate the dishes for
48 hours at a constant temperature of 35 C. (950 F.).
At the end of the period of incubation, place petri dishes on
a counting plate and count the number of colonies per plate, us-
. ing the 21/2 power magnifying glass to aid in observing the col-
onies. A petri dish must show from 30 to 300 colonies and the
number of bacteria per ml. of sample is figured by multiplying
the number of colonies per petri dish by the dilution.

The Direct Microscopic Count
Purpose
To determine the number and types of bacteria present in
milk.
Principle
Individual bacteria or groups of bacteria in a definite measured
quantity of milk are stained with a dye which makes them easy
to distinguish and enumerate when the sample of milk is ex-
amined with the microscope.

Materials Required
Microscope with ocular magnification of 6.4x or lOx and an oil immer-
sion lens







Florida Agricultural Experiment Station


Capillary pipette graduated to deliver exactly 0.01 ml.
Glass or cardboard guides 2 x 4,1/ inches with 16 areas, each 1 square
centimeter in size
Glass microscopic slides 1 x 3 inches or 2 x 4% inches
Staining jar
Ethyl alcohol 90 percent
Xylene
Methylene blue stain.

Procedure

1. Mix sample thoroughly.
2. Place glass slide over guide plate and with a pipette deliver
0.01 ml. of milk or cream onto the slide and spread it with a clean
bacteriological needle over an area of 1 square centimeter.
3. Set slide on a warm level surface and allow to dry thor-
oughly.
4. After drying, place the slides in xylene for one to two min-
utes to dissolve out the fat and again allow them to drain and
dry.
5. Immerse in 90 percent ethyl alcohol for one to two minutes
and then immerse in a stain of methylene blue just long enough
to show a faint blue tint.
6. Drain slides and dry by blotting with a paper towel.
7. Place slide under a properly standardized microscope and
count bacteria in a number of microscopic fields.
8. Multiply the average number of bacteria per field by a
factor determined as follows:
a. By means of a stage micrometer measure the diameter of
the field. (If a monocular microscope is used, see that the
draw tube is in the proper position.)
b. Calculate the area of the microscopic field.
Area = pi times radius squared.
Area = area of microscopic field in square centimeters.
Radius = radius of microscopic field in centimeters.
Pi = 3.1416.
c. Since the area of the film of milk is 1 sq. cm., the next step
is to determine the number of fields in the film.
1
The number of fields in the film will be
A (area)
1
d. Since the film of milk is -1 ml. by volume, the number of
100
microscopic fields in 1 ml. of milk would be A
e. To determine the number of bacteria per milliliter, multiply








A Laboratory Program for the Dairy Plant


the average number of bacteria per field by the microscopic
factor.
Determining the factor:
Diameter of microscopic field = 0.16 mm. or 0.016 cm.
Radius of microscopic field = 0.008 cm.
Area = pi times radius squared or
Area = 3.1416 x 0.000064, which is 0.0002 sq. cm.
100
Factor = ( ) which is 500,000.
A (.0002)
To reduce the factor to about 300,000, employ an ocular giving
a magnification of 6.4x.

Total Solids Test
Principle
All moisture is driven from the sample of any dairy product,
leaving the dried solids.
The percentage of moisture subtracted from 100 gives the per-
cent solids.
Materials Required
Analytical balance (chainomatic with vernier scale capable of weigh-
ing 0.0001 gm.)
1 set analytical weights ranging from 0.1 to 100 grams
1 Bunsen burner
Aluminum solids dish 1 inch high x 3 inch diameter with flat bottom
1 drying oven
Aluminum cover for solids dish
1 desiccator.
Procedure
1. Dry pan or dish to constant weight over a low flame or in
constant temperature oven at about 1000 C.
2. Cool pan in desiccator and weigh accurately. Record
weight.
3. Place 3 to 5 ml. of well mixed sample in the dish and weigh
accurately. Record weight.
4. Cover solids dish with aluminum cover and place in a dry-
ing oven heated to a temperature of 1000 C. (2120 F.) and dry to
constant weight.
5. Cool in a desiccator and weigh rapidly to avoid increase in
weight due to absorption of moisture.
6. Calculate the percent of moisture as follows: Example:







Florida Agricultural Experiment Station


Weight of pan + milk = 20.00 grams
Weight of pan empty = 15.00 grams
Weight of milk = 5.00 grams
Weight of pan + dried milk = 15.63 grams
Weight of pan empty = 15.00 grams
Weight of dried milk = 0.63 grams
5.00 0.63 = 4.37 grams of moisture evaporated.
4.37 x 100 = 87.4 percent moisture.
5.00
100 87.4 = 12.6 percent solids.

Sediment Test
Principle
The'sediment tester works on the principle of a very fine mesh
strainer.

Materials Required
Sediment tester
-Cotton discs for tester
Pint dipper.

Sediment Test for Bottled Milk
Procedure
1. Warm milk sample to 900 F. and thoroughly mix.
2. Place a cotton sediment disc in the sediment tester, making
certain the disc is absolutely free of all foreign materials.
3. Add 1 pint of the warmed milk sample to the tester and
filter.
4. Remove the disc and allow it to dry either at room temper-
ature or in a 1000 F. oven. Exercise care so that dust and dirt
will not be deposited on the disc during the drying period.
5. The amount of sediment on the pad indicates the care used
in the production and handling of the milk.

Sediment Test for Milk in 10-Gallon Cans
Procedure
1. Wash and sterilize sediment tester.
2. Place a cotton sediment disc in the tester, making certain
the disc is absolutely free from all foreign material.
3. With the tester handle all the way down, insert the tester
to the bottom of the can.
4. Slowly raise the handle to the top of the tester, and while
raising the handle, make a sweeping motion over the bottom of
the can.
5. After filling the tester and before removing from the can,







Florida Agricultural Experiment Station


Weight of pan + milk = 20.00 grams
Weight of pan empty = 15.00 grams
Weight of milk = 5.00 grams
Weight of pan + dried milk = 15.63 grams
Weight of pan empty = 15.00 grams
Weight of dried milk = 0.63 grams
5.00 0.63 = 4.37 grams of moisture evaporated.
4.37 x 100 = 87.4 percent moisture.
5.00
100 87.4 = 12.6 percent solids.

Sediment Test
Principle
The'sediment tester works on the principle of a very fine mesh
strainer.

Materials Required
Sediment tester
-Cotton discs for tester
Pint dipper.

Sediment Test for Bottled Milk
Procedure
1. Warm milk sample to 900 F. and thoroughly mix.
2. Place a cotton sediment disc in the sediment tester, making
certain the disc is absolutely free of all foreign materials.
3. Add 1 pint of the warmed milk sample to the tester and
filter.
4. Remove the disc and allow it to dry either at room temper-
ature or in a 1000 F. oven. Exercise care so that dust and dirt
will not be deposited on the disc during the drying period.
5. The amount of sediment on the pad indicates the care used
in the production and handling of the milk.

Sediment Test for Milk in 10-Gallon Cans
Procedure
1. Wash and sterilize sediment tester.
2. Place a cotton sediment disc in the tester, making certain
the disc is absolutely free from all foreign material.
3. With the tester handle all the way down, insert the tester
to the bottom of the can.
4. Slowly raise the handle to the top of the tester, and while
raising the handle, make a sweeping motion over the bottom of
the can.
5. After filling the tester and before removing from the can,








A Laboratory Program for the Dairy Plant


push the handle all the way down, forcing all the milk through
the cotton sediment disc.
6. Remove the disc and dry as in the test for bottled milk.

The Methylene Blue Reduction Test
Principle
The decoloration of the blue dye depends upon the removal of
oxygen from the methylene blue by vital activities of bacteria.
The rate of decolorization is related to the number' of bacteria
present and this in turn depends largely upon the care exercised
in producing and handling the milk.

Materials Required
Heavy walled test tubes 6 inches long x % inch diameter
10 ml. dipper or 10 ml. pipettes
1 ml. pipette or a burette graduated to deliver 1 ml. portions.
1 thermostatically controlled electric water bath complete with cover,
test tube racks and thermometer
Methylene blue thiocyanate tablets (Certified Biological Stain, Na-
tional).
Procedure
1. Clean, and sterilize by boiling, test tubes, dipper and pip-
ettes.
2. Prepare the methylene blue solution according to the direc-
tions on the bottle. One tablet in 200 ml. sterile water.
3. Transfer 1 ml. of the properly prepared methylene blue
solution to each test tube.
4. Transfer 10 ml. of each sample to be tested to each test
tube containing the methylene blue solution.
5. Allow the tubes to incubate in the covered water bath for
several hours at 98.60 F. and observe the color of the milk at the
intervals specified below. Milk may be classified as follows, ac-
cording to the rapidity of decolorizing.
Approximate Number Classification
Time to Decolorize of Bacterial Present per MI. of Milk
20 minutes or less 20,000,000 or over Very bad
20 minutes to 2 hours 4,000,000 to 20,000,000 Bad
2 hours to 5% hours 500,000 to 4,000,000 Fair
5%/ hours or over Less than 500,000 Good

Use of the Lactometer
Principle
In skimmed or partly skimmed milk the lactometer sinks to a
lesser depth than in whole milk or very rich milk. If fat is re-








A Laboratory Program for the Dairy Plant


push the handle all the way down, forcing all the milk through
the cotton sediment disc.
6. Remove the disc and dry as in the test for bottled milk.

The Methylene Blue Reduction Test
Principle
The decoloration of the blue dye depends upon the removal of
oxygen from the methylene blue by vital activities of bacteria.
The rate of decolorization is related to the number' of bacteria
present and this in turn depends largely upon the care exercised
in producing and handling the milk.

Materials Required
Heavy walled test tubes 6 inches long x % inch diameter
10 ml. dipper or 10 ml. pipettes
1 ml. pipette or a burette graduated to deliver 1 ml. portions.
1 thermostatically controlled electric water bath complete with cover,
test tube racks and thermometer
Methylene blue thiocyanate tablets (Certified Biological Stain, Na-
tional).
Procedure
1. Clean, and sterilize by boiling, test tubes, dipper and pip-
ettes.
2. Prepare the methylene blue solution according to the direc-
tions on the bottle. One tablet in 200 ml. sterile water.
3. Transfer 1 ml. of the properly prepared methylene blue
solution to each test tube.
4. Transfer 10 ml. of each sample to be tested to each test
tube containing the methylene blue solution.
5. Allow the tubes to incubate in the covered water bath for
several hours at 98.60 F. and observe the color of the milk at the
intervals specified below. Milk may be classified as follows, ac-
cording to the rapidity of decolorizing.
Approximate Number Classification
Time to Decolorize of Bacterial Present per MI. of Milk
20 minutes or less 20,000,000 or over Very bad
20 minutes to 2 hours 4,000,000 to 20,000,000 Bad
2 hours to 5% hours 500,000 to 4,000,000 Fair
5%/ hours or over Less than 500,000 Good

Use of the Lactometer
Principle
In skimmed or partly skimmed milk the lactometer sinks to a
lesser depth than in whole milk or very rich milk. If fat is re-







Florida Agricultural Experiment Station


moved from a sample, the lactometer floats higher, since it is
floating in partially skimmed milk. Conversely, if water is
added, the lactometer sinks to a lower depth, since water is
lighter than milk. The lactometer is graduated to indicate sp.
gr. of milk.
Materials Required
Babcock testing equipment
Quevenne lactometer
Fahrenheit thermometer
Lactometer cylinder
Containers for mixing pint samples of milk.

Procedure
1. Hold samples at 36 to 400 F. until ready to examine.
2. Warm samples to 1150 F., hold for 1/? minute and then cool
to 600 F.
3. Mix the milk thoroughly by pouring from one container to
another three or four times.
4. Adjust the temperature of the milk to a point near 600 F.
between 50 to 700 F. and fill the cylinder to within 11/2 inches of
top.
5. Wash the lactometer in cool water, dry it and lower it slow-
ly until it floats freely in the milk in the cylinder.
6. After the lactometer floats at equilibrium, read its scale at
the top of the meniscus. Immediately afterward read the ther-
mometer. Record these readings and correct for temperature.
7. To correct the lactometer reading for temperature add 0.1
to the lactometer reading for each degree above 60 F. or sub-
tract 0.1 from the lactometer reading for each degree below 600
F. After the correction is made, the value is referred to as the
corrected lactometer (C.L.).
8. Determine the butterfat content of the milk by the Babcock
test or other recognized method.
9. To calculate the percentage of total solids (T.S.), substitute
the proper values in the following formula:
C.L.
Percent TS 4 + (1.2 x percent of fat)
10. To calculate the percentage of solids-not-fat (S.N.F.),
substitute the proper values in the following formula:
C.L.
Percent SNF =-- + (0.2 x percent of fat)
11. The specific gravity may be calculated by substituting the
proper value in the following formula:
C.L.
Specific Gravity C.L. 1
1,000








A Laboratory Program for the Dairy Plant


12. After making the butterfat test, and calculations to deter-
mine total solids (T.S.) and solids-not-fat (S.N.F.), compare
these results with those shown in Table 1 to determine if the
sample tested is of normal composition.

TABLE 1.-RELATION OF FAT TO OTHER SOLIDS IN MILK OF NORMAL
COMPOSITION.'
Fat Solids-not-fat Total Solids
Percent Percent Percent
3.0 8.33 11.33
3.1 8.40 11.50
3.2 8.46 11.66
3.3 8.52 11.82
3.4 8.55 11.95
3.5 8.60 12.10
3.6 8.65 12.25
3.7 8.69 12.39
3.8 8.72 12.52
3.9 8.76 12.66
4.0 8.79 12.79
4.1 8.82 12.92
4.2 8.86 13.06
4.3 8.89 13.19
4.4 8.92 13.32
4.5 8.95 13.45
4.6 8.98 13.58
4.7 9.01 13.71
4.8 9.04 13.84
4.9 9.07 13.97
5.0 9.10 14.10
iFrom Market Milk, Kelly and Clement, John Wiley and Sons. 1923.

The Acidity Test
Principle
The acidity of milk is due to the presence of acid salts and to
the acid formed by bacterial action. If an alkaline solution of
definite strength is employed to neutralize the acidity its equiva-
lent in terms of percent of total acid may be readily calculated.

Materials Required
Tenth normal sodium hydroxide (alkali). This reagent may be obtained
already prepared from a dairy supply house.
White cup
17.6 ml. pipette
9 ml. pipette
Phenolphthalein indicator made by dissolving 1 gram of powder in 30
ml. of denatured alcohol
Glass stirring rod
50 ml. burette graduated in 0.1 ml. for measuring alkali used
Burette clamp and support.
NOTE: The Nafis automatic acidity tester complete with in-
struction for use may be supplied by most dairy equipment sup-
ply companies.







Florida Agricultural Experiment Station


Procedure
1. Place 17.5 ml. of milk in a white cup and rinse out the
pipette with an equal amount of distilled water, also adding this
to the cup.
2. Add three drops of phenolphthalein indicator.
3. From the burette run in slowly the standard alkali solu-
tion, constantly stirring the mixture in the cup until it turns to
a faint pink color. This is the endpoint and all acid is neutral-
ized.
4. Calculate the percent of acid using the following formula:
M1. of alkali used x .009
Percent of acid G s of s e x 100
Grams of sample used
With non-viscous products such as milk, skimmilk and light
cream, weighing is not essential. Measuring will give dependable
results for all practical purposes and save time. By using the
formula, any size sample may be used and accurate determina-
tions can be made as long as the weight of the sample is known.
Viscous products such as cream, ice cream mix and cultured but-
termilk must be weighed on cream balances or other suitable
scales and then diluted with an equal amount of distilled water.

The Chlorine Test
Purpose
To determine the correct strength of chlorine sterilizing solu-
tions.

Principle
Free chlorine in the acidified rinse water 'liberates a cor-
responding number of molecules of iodine from potassium iodide,
resulting in a yellowish color. The sodium thiosulphate reacts
with the liberated iodine, forming a colorless compound.

Materials Required
250 ml. Erlenmeyer flask
1,000 ml. volumetric flask
50 ml. volumetric pipette
50 ml. burette graduated in tenths
Tenth normal sodium thiosulfate solution
99.5 percent acetic acid
Potassium iodide crystals or powder
2 percent starch solution indicator.







A Laboratory Program for the Dairy Plant


Testing Chlorine Rinse Water
Procedure
1. Transfer 50 ml. of the chlorine rinse water to the 25 ml.
Erlenmeyer flask.
2. Dissolve 1 to 2 grams of potassium iodide in the chlorine
rinse water.
3. Add 10 ml. of acetic acid. The presence of free chlorine is
indicated by a yellow color.
4. Titrate the solution with tenth normal sodium thiosulfate
until the yellow color almost disappears.
5. Add 2 ml. of the starch indicator and continue the titra-
tion until the blue color just disappears.
6. To calculate the parts per million (p.p.m.) of available
chlorine in the rinse water, multiply the number of cubic centi-
meters of sodium thiosulfate used by 70.9.
The percentage of available chlorine is obtained by multiply-
ing the number of milliliters of sodium thiosulfate by 0.00709.

Testing Chlorine Stock Solution
1. Dilute 1 ml. of stock solution with 999 ml. of distilled water
and proceed as in test for rinse water.
2. In making calculations multiply results by 1,000.

Alkali Test
Purpose
To determine strength of soaker solutions in mechanical milk
bottle washers.
Principle
If an acid solution of definite strength is used to neutralize
an alkaline solution, its equivalent in terms of percent of total
alkali may be readily determined.

Materials Required
50 ml. pipette
50 ml. burette graduated in tenths
Burette stand
5 ml. pipette
200 ml. Erlenmeyer flask
250 ml. volumetric flask
Tenth normal sulfuric acid (May be purchased already prepared from
any chemical supply house)
Phenolphthalein indicator 0.5 percent solution in 50 percent alcohol
Methyl orange indicator 0.05 percent solution in distilled water.







A Laboratory Program for the Dairy Plant


Testing Chlorine Rinse Water
Procedure
1. Transfer 50 ml. of the chlorine rinse water to the 25 ml.
Erlenmeyer flask.
2. Dissolve 1 to 2 grams of potassium iodide in the chlorine
rinse water.
3. Add 10 ml. of acetic acid. The presence of free chlorine is
indicated by a yellow color.
4. Titrate the solution with tenth normal sodium thiosulfate
until the yellow color almost disappears.
5. Add 2 ml. of the starch indicator and continue the titra-
tion until the blue color just disappears.
6. To calculate the parts per million (p.p.m.) of available
chlorine in the rinse water, multiply the number of cubic centi-
meters of sodium thiosulfate used by 70.9.
The percentage of available chlorine is obtained by multiply-
ing the number of milliliters of sodium thiosulfate by 0.00709.

Testing Chlorine Stock Solution
1. Dilute 1 ml. of stock solution with 999 ml. of distilled water
and proceed as in test for rinse water.
2. In making calculations multiply results by 1,000.

Alkali Test
Purpose
To determine strength of soaker solutions in mechanical milk
bottle washers.
Principle
If an acid solution of definite strength is used to neutralize
an alkaline solution, its equivalent in terms of percent of total
alkali may be readily determined.

Materials Required
50 ml. pipette
50 ml. burette graduated in tenths
Burette stand
5 ml. pipette
200 ml. Erlenmeyer flask
250 ml. volumetric flask
Tenth normal sulfuric acid (May be purchased already prepared from
any chemical supply house)
Phenolphthalein indicator 0.5 percent solution in 50 percent alcohol
Methyl orange indicator 0.05 percent solution in distilled water.







Florida Agricultural Experiment Station


Procedure
1. Transfer 5 ml. of the bottle-washing solution to a 250 ml.
volumetric flask and make up to the mark with distilled water.
2. After mixing well, transfer 50 ml. of this solution to an
Erlenmeyer flask. Add a few drops of phenolphthalein indica-
tor and titrate with tenth normal sulfuric acid to a colorless so-
lution. Record the quantity of acid used. This is titration A.
3. Add to this same solution in the Erlenmeyer flask a few
drops of methyl orange indicator and continue the titration with
the normal sulfuric acid until a slight pink color appears. The
amount of acid used in this second titration is recorded as titra-
tion B.
4. Make calculations as follows:
Percent caustic NaOH = ml. titration A ml. titration B x 0.4.
Percent total alkali = ml. titration A + ml. titration B x 0.4.

A.B.C.B. Caustic Test
Purpose
To make a rough estimation of the strength of soaker solution
in bottle washers:

Principle
This test is based on the color change of an indicator com-
pound which is orange colored in alkaline solution but which
changes to a lemon yellow color at or near the neutral point.

Materials Required
10 ml. graduated cylinder
Glass tumbler
Stirring rod
A.B.C.B. caustic test preliminary tablet No. 1
A.B.C.B. caustic test tablet No. 2.
Procedure
1. Measure 10 ml. of cool soaker solution into the clean glass
tumbler.
2. Add one preliminary tablet No. 1 and crush with stirring
rod. Do not add any more of these tablets.
3. When tablet No. 1 is completely dissolved, add one caustic
test tablet No. 2 and dissolve with the aid of the stirring rod.
If the color is brick red, the strength of the solution is more
than 1/2 percent.







A Laboratory Program for the Dairy Plant


4. Add caustic tablets No. 2, one at a time, completely dis-
solving each tablet until a lemon yellow color appears.
5. Each caustic tablet required to produce a lemon yellow
color represents 1/2 percent caustic strength. To determine the
total caustic strength in percentage, divide the total caustic tab-
lets used by 2.

The Phosphatase Test. Sharer Field Test
Purpose
To determine the efficiency of pasteurization.
Principle
This test is based on the detection of phosphatase enzyme, a
constituent of raw milk, which is inactivated by pasteurizing at
1430 F. for 30 minutes or 1600 F. for 15 seconds. This enzyme,
even in small quantity, is readily detected through its action on
a phenyl phosphoric ester, liberating free phenol which in turn
is measured quantitatively by adding 2, 6 dibromoquinone-
chloroimide (BQC) to form an indophenol blue.
Materials Required
The "Phax-Kit" Model B and accessories, consisting of water bath,
thermometer and normal butyl alcohol may be purchased from any dairy
laboratory supply company.
Methyl alcohol.
Reagents
Prepare reagents as follows:
Reagent A:
1. Crush one Phos-Phax (white) tablet in test tube and dis-
solve in 5 ml. distilled water.
2. Add two drops of fresh BQC reagent made as directed be-
low; shake.
3. Allow five minutes for color development, then extract any
indophenol blue that appears by shaking vigorously with 2 ml.
n-butyl alcohol.
4. Allow to stand until alcohol separates at top. Remove al-
cohol with medicine dropper and discard.
5. Dilute remainder of the reagent to 50 ml. This reagent is
phenol-free and is suitable for use as the substrate.
Reagent B:
1. Dissolve one Indo-Phax (yellow) tablet in 5 ml. of 95 per-
cent ethyl alcohol or pure methyl alcohol. This is the BQC re-







Florida Agricultural Experiment Station


agent mentioned above. Do not use denatured alcohol. Transfer
to a dropping bottle.

Procedure
1. Fill graduated tube to the first ring (5 ml.) with the sub-
strate, reagent A, bringing the top of the meniscus to the ring.
2. Add sample of milk to be tested until the top of the menis-
cus reaches the second ring (1/2 ml.).
3. Shake the tube briefly, then place it in an incubator at 980
F. for 10 minutes.
4. After 10 minutes, remove the tube from the water bath
and add 6 drops of BQC (reagent B).
5. Shake well immediately and let stand for five minutes.
6. Interpret the results as follows:
(a) If the blue tint is scarecly perceptible or doubtful, add
normal butyl alcohol until the top of the meniscus reaches the
top ring (2 ml.).
(b) Invert the tube, allowing the bubbles to subside after
each inversion before re-inverting the blue. Repeat 10 times.
(Too rapid inversion results in an emulsion that does not easily
separate.) When this step is properly performed the butyl alco-
hol will separate in a clear layer about 3/4 inch in height.
(c) Any indo-phenol blue is concentrated in this clear layer.
Compare with the liquid standards by holding the filter sheet be-
tween the tubes and the light.
(d) Milk properly pasteurized under commercial conditions at
1430 F. for 30 minutes or 1600 F. for 15 seconds will give defin-
itely less color than the 2-unit standard.

Efficiency of Homogenization
Purpose
To observe the extent to which the homogenizer or viscolizer
breaks up and disperses the fat globules in homogenized dairy
products.

Principle
The microscope, under high power, can be used to observe the
size of the fat globules in a dairy product before and after ho-
mogenization and in this way make an estimate of homogenizing
efficiency by comparing the size of the fat globules and the ex-
tent of clumping of the globules before and after homogenizing.








A Laboratory Program for the Dairy Plant


Materials Required
Microscope fitted with oil immersion objective and 1Ox eyepiece
Glass microscopic slides with concave depression for preparing hanging
drop
Glass cover slips
100 ml. graduated cylinder
Inoculating loop
150 ml. test tube for dilution
1 ml. pipette graduated 0.1 ml.
Procedure
1. Dilute sample to be tested with distilled water so that the
diluted sample contains 0.1-0.2% butterfat. The following table
gives the approximate dilutions to use.
Milk dilute 1 ml. with 25 ml. of distilled water.
20% cream dilute 1 ml. with 150 ml. of distilled water.
30% cream dilute 1 ml. with 225 ml. of distilled water.
40% cream dilute 1 ml. with 300 ml. of distilled water.
10% ice cream mix dilute 1 ml. with 75 ml. of distilled water.
20% ice cream mix dilute 1 ml. with 150 ml. of distilled water.

2. After proper dilution is made transfer at once 0.01 ml. of
the sample with the inoculating loop to a clean glass cover slip.
3. Invert cover slip with sample over the concave portion of
the glass microscopic slide and observe immediately with the high
power oil immersion lens.
4. The size of the fat globules may be measured with the aid
of an eyepiece micrometer which has been calibrated against a
stage micrometer, but this is usually not practical for routine ex-
amination. Practice with a large number of samples produced
under varying conditions will give an idea of the general size and
appearance of what the fat globules should be.

Miscellaneous Supplies and Materials
In addition to the materials required as indicated for each
specific test, a well equipped laboratory should have available a
miscellaneous assortment of laboratory supplies. This list should
include such items as follows:
Test tubes, pipettes, graduated cylinders, beakers, flasks (Erl-
enmeyer, volumetric), rubber stoppers, cork stoppers, rubber tub-
ing, assorted glass bottles, glass tubing, assorted laboratory
brushes, sample bottles, stirring rods, glass funnels, thermom-
eters, cork borers, ringstands, support rings with clamp, wire
gauze square (asbestos and plain), iron tripod, Bunsen burners
.or alcohol burners, filter paper, cheesecloth, wax china marking







30 Florida Agricultural Experiment Station

pencils (black, red), electric hot plate, hand tally counter, inter-
val timer, heavy duty laboratory balance, first aid kit and a cul-
ture incubator.
From the standpoint of cost, it is economical for the laboratory
operator to purchase pure chemical reagents for the preparation
of standard solutions, indicators, stains, dye and bacteriological
media. This procedure, however, requires special knowledge and
skill on the part of the operator, and extreme care and exactness
in preparing these materials. Experience has proven that for
the average small dairy plant it is usually more satisfactory for
the operator to purchase these materials already prepared in the
exact strength needed ready for use. Most chemical supply
houses and dairy supply companies carry a complete stock of
chemical supplies for the milk plant laboratory.




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