Group Title: Bulletin University of Florida. Agricultural Experiment Station
Title: Effect of processing upon the nutritive value of milk as evaluated with rats
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Permanent Link: http://ufdc.ufl.edu/UF00026841/00001
 Material Information
Title: Effect of processing upon the nutritive value of milk as evaluated with rats
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 12 p. : charts ; 23 cm.
Language: English
Creator: Abbott, O. D ( Ouida Davis ), b. 1892
French, R. B ( Rowland Barnes )
Townsend, Ruth O
Publisher: University of Florida Agricultural Experiment Station
Place of Publication: Gainesville Fla
Publication Date: 1951
Copyright Date: 1951
 Subjects
Subject: Milk as food   ( lcsh )
Milk -- Composition   ( lcsh )
Dairy processing   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
non-fiction   ( marcgt )
 Notes
Statement of Responsibility: O.D. Abbott, R.B. French and Ruth O. Townsend.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026841
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: ltuf - AEN6401
oclc - 18266201
alephbibnum - 000925745

Full Text


Bulletin 485 November 1951


UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATIONS
WILLARD M. FIFIELD, Director
GAINESVILLE, FLORIDA











Effect of Processing upon the Nutritive

Value of Milk as Evaluated with Rats


O. D. ABBOTT, R. B. FRENCH and RUTH O. TOWNSEND




















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










BOARD OF CONTROL EDITORIAL
J. Francis Cooper, M.S.A., Editor3
Frank M. Harris, Chairman, St. Petersburg Clyde Beale, A.B.J., Associate Editor3
Hollis Rinehart, Miami L. Odell Griffith, B.A.J., Asst. Editors
Eli H. Fink, Jacksonville J. N. Joiner, B.S.A., Assistant Editor 3
George J. White, Sr., Mount Dora
Mrs. Alfred I. duPont, Jacksonville
George W. English, Jr., Ft. Lauderdale ENTOMOLOGY
W. Glenn Miller, Monticello A. N. Tissot, Ph.D., Entomologist
W. F. Powers, Secretary, Tallahassee L. C. Kuitert, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
EXECUTIVE STAFF F. A. Robinson, M.S., Asst. Apiculturist
J. Hillis Miller, Ph.D., President 3
J. Wayne Reitz, Ph.D., Provost for Agr.3
WllarJ M. Fifield, M.S., Director HOME ECONOMICS
J. R. Beckenbach, Ph.D., Asso. Director Ouida D. Abbott, Ph.D., Home Econ.i
L. 0. Gratz, Ph.D., Asst. Dir., Research R. B. French, Ph.D., Biochemist
Geo. F. Baughman, M.S., Business Mgr.3
Rogers L. Bartley, B.S., Admin. Mgr.3
Claranelle Alderman, Accountant HORTICULTURE
G. H. Blackmon, M.S.A., Horticulturist
MAIN STATION, GAINESVILLE F. S. Jamison, Ph.D., Horticulturist3
Albert P. Lorz, Ph.D., Horticulturist
AGRICULTURAL ECONOMICS R. K. Showalter, M.S., Asso. Hort.
H. G. Hamilton, Ph.D., Agr. Economist 3 R. A. Dennison, Ph.D., Asso. Hort.
R. E. L. Greene, Ph.D., Agr. Economist R. H. Sharpe, M.S., Asso. Horticulturist
M. A. Brooker, Ph.D., Agr. Economist V. F. Nettles, Ph.D., Asso. Horticulturist
Zach Savage. M.S.A., Associate F. S. Lagasse, Ph.D., Asso. Hort.2
A. H. Spurlock, M.S.A., Associate R. D. Dickey, M.S.A., Asso. Hort.
D. E. Alleger, M.S., Associate L. H. Halsey, M.S.A., Asst. Hort.
D'. L. Brooke, M.S.A., Associate4 C. D. Hall, Ph.D., Asst. Horticulturist
M. R. Godwin, Ph.D., Associate Austin Griffiths, Jr., B.S., Asst. Hort.
H. W. Little, M.S., Assistant S. E. McFadden, Jr., Ph.D., Asst. Hort.
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D. C. Kimmel, Ph.D., Assistant
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Orlando, Florida (Cooperative USDA)
G. Norman Rose, B.S., Asso. Agr. Economist PLANT PATHOLOGY
J. C. Townsend, Jr., B.S.A., Agr.
Statistician 2 BSA A W. B. Tisdale, Ph.D., Plant Pathologist 3
J. B. Owens, B.S.A., Agr. Statistician Phares Decker, Ph.D., Plant Pathologist
Erdman West, M.S., Mycologist and Botanist
Robert W. Earhart, Ph.D., Plant Path.2
AGRICULTURAL ENGINEERING Howard N. Miller, Ph.D., Asso. Plant Path.
Frazier Rogers, M.S.A., Agr. Engineer 1 Lillian E. Arnold, M.S., Asst. Botanist
J. M. Johnson, B.S.A.E., Agr. Eng.3 C. W. Anderson, Ph.D., Asst. Plant Path.
J. M. Myers, B.S., Asso. Agr. Engineer
R. E. Choate, B.S.A.E., Asso. Agr. Eng.3 P LT HU AN
A. M. Pettis, B.S.A.E., Asst. Agr. Eng.2 POULTRY HUSBANDRY
N. R. Mehrhof, M.Agr., Poultry Husb.13
AGRONOMY J. C. Driggers, Ph.D., Asso. Poultry Husb.
Fred H. Hull, Ph.D., Agronomist
G. B. Killinger, Ph.D., Agronomist
H. C. Harris, Ph.D., Agronomist SOILS
R. W. Bledsoe, Ph.D., Agronomist F. B. Smith, Ph.D., Microbiologist 13
W. A. Carver, Ph.D., Associate Gaylord M. Volk, Ph.D.. Soils Chemist
Darrel D. Morey, Ph.D., Assoc:ate J. R. Henderson, M.S.A., Soil Technologist3
Fred A. Clark, B.S., Assistant J. R. Neller, Ph.D., Soils Chemist
Myron C. Grennell, B.S.A.E., Assistant Nathan Gammon, Jr., Ph.D., Soils Chemist
E. S. Horner, Ph.D., Assistant Ralph G. Leighty, B.S., Asst. Soil Surveyor
A. T. Wallace, Ph.D., Assistant G. D. Thornton, Ph.D., Asso. Microbiologist a3
D. E. McCloud; Ph.D., Assistant C. F. Eno, Ph.D., Asst. Soils Microbiologist
H. E. Buckley. B.S.A., Assistant H. W. Winsor, B.S.A., Assistant Chemist
R. E. Caldwell, M.S.A., Asst. Chemist'4
ANIMAL HUSBANDRY AND NUTRITION V. W. Carlisle, B.S., Asst. Soil Surveyor
T. J. Cunha, Ph.D., An. Husb.'3 James H. Walker, M.S.A., Asst. Soil
G. K. Davis, Ph.D., Animal Nutritionist3 Surveyor
J. E. Pace, M.S., Asst. An. Husb.3 S. N. Edson, M.S., Asst. Microbiologist
S. John Folks, M.S., Asst. An. Husb.4 Fred E. Koehler, Ph.D., Asst. Soil Micro-
Katherine Boney, B.S., Asst. Chem. biologist
A. M. Pearson, Ph.D., Asso. An. Husb.3 William K. Robertson, Ph.D., Asst. Chemist
John D. Feaster, Ph.D., Asst. An. Nutri. O. E. Cruz, B.S.A., Asst. Soil Surveyor
H. D. Wallace, Ph.D., Asst. An. Husb.3 W. G. Blue, Ph.D., Asst. Biochemist
M. Koger, Ph.D., An. Husbandman 3 J. G. A. Fiskel, Ph.D., Asst. Biochemist
DAIRY SCIENCE
"DAIRY SCI C VETERINARY SCIENCE
E. L. Fouts, Ph.D., Dairy Tech.3
R. B. Becker, Ph.D., Dairy Husb.3 D. A. Sanders, D.V.M., Veterinarian
S. P. Marshall, Ph.D., Asso. Dairy Husb.3 M. W. Emmel, D.V.M., Veterinarian 3
W. A. Krienke, M.S.. Asso. in Dairy Mfs.3 C. F. Simpson, D.V.M., Asso. Veterinarian
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.2 L. E. Swanson, D.V.M., Parasitologist
Leon Mull, Ph.D., Asso. Dairy Tech. Glenn Van Ness, D'.V.M., Asso. Poultry
H. Wilkowske, Ph.D., Asst. Dairy Tech. Pathologist
James M. Wing, M.S., Asst. Dairy Husb. G. E. Batte, D.V.M., Asso. Parasitologist










BRANCH STATIONS SUB-TROPICAL STATION, HOMESTEAD
Geo. D. Ruehle, Ph.D., Vice-Dir. in Charge
NORTH FLORIDA STATION, QUINCY D. 0. Wolfenbarger, Ph.D., Entomologist
Francis B. Lincoln, Ph.D., Horticulturist
J. D. Warner, M.S., Vice-Director in Charge Robert A. Conover, Ph.D., Plant Path.
R. R. Kincaid, Ph.D., Plant Pathologist John L. Malcolm, Ph.D., Asso. Soils Chemist
L. G. Thompson, Ph.D., Soils Chemist R. W. Harkness, Ph.D., Asst. Chemist
W. C. Rhoads, M.S., Entomologist R. Bruce Ledin, Ph.D., Asst. Hort.
W. H. Chapman, M.S., Asso. Agronomist
Frank S. Baker, Jr., B.S., Asst. An. Hush. WEST CENTAL FLORIDA STATION,
BROOKSVILLE
Mobile Unit, Monticello William Jackson, B.S.A., Animal Husband-
R. W. Wallace, B.S., Associate Agronomist man in Charge 2

Mobile Unit, Marianna RANGE CATTLE STATION, ONA
W. G. Kirk, Ph.D., Vice-Director in Charge
R. W. Lipscomb, M.S., Associate Agronomist E.M. edges, Ph.D., Agronomist
U. W. Jones, M.S., Asst. Soil Technologist
Mobile Unit, Pensacola
R. L. Smith, M.S., Associate Agronomist CENTRAL FLORIDA STATION, SANFORD
R. W. Ruprecht, Ph.D., Vice-Dir. in Charge
J. W. Wilson, Sc.D., Entomologist
Mobile Unit, Chipley P. J. Westgate, Ph.D., Asso. Hort.
J. B. White, B.S.A., Associate Agronomist Ben. F. Whitner, Jr., B.S.A., Asst. Hort.
Geo. Swank, Jr., Ph.D., Asst. Plant Path.
CITRUS STATION, LAKE ALFRED
A. F. Camp, Ph.D., Vice-Director in Charge WEST FLORIDA STATION, JAY
W. L. Thompson, B.S., Entomologist C. E. Hutton, Ph.D., Vice-Director in Charge
R. F. Suit, Ph.D., Plant Pathologist
. P. Dcharme Ph.D., Asso. Plant Path. H. W. Lundy, B.S.A., Associate Agronomist
C. R. Stearns, Jr., B.S.A., Asso. Chemist W. R. Langford, Ph.D., Asst. Agron.
J. W. Sites, Ph.D., Horticulturist
H. O. Sterling, B.S., Asst. Horticulturist SUWANNEE VALLEY STATION,
H. J. Reitz, Ph.D., Horticulturist LIVE OAK
Francine Fisher, M.S., Ast. Plant Path. G. E. Ritchey, M.S., Agronomist in Charge
I. W. Wander, Ph.D., Soils Chemist
J. W. Kesterson, M.S., Asso. Chemist
R. Hendrickson, B.S., Asst. Chemist GULF COAST STATION, BRADENTON
Ivan Stewart, Ph.D., Asst. Biochemist E. L. Spencer, Ph.D., Soils Chemist in Charge
D. S. Presser, Jr., B.S., Asst. Horticulturist E. G. Kelsheimer, Ph.D., Entomologist
R. W. Olsen, B.S., Biochemist David G. Kelbert, Asso. Horticulturist
F. W. Wenzel, Jr., Ph.D., Chemist
Alvin H. Rouse, M.S., Asso. Chemist Robert Magie, Ph.D., Plant Pathologist
Alvin H. Rouse, M.S., Asso. Chemist
H. W. Ford, Ph.D., Asst. Horticulturist J. M. Walter, Ph.D., Plant Pathologist
L. W. Faville, Ph.D., Asst. Bacteriologist Donald S. Burgis, M.S.A., Asst. Hort.
L. C. Knorr, Ph.D., Asso. Histologist C. M. Geraldson, Ph.D., Asst. Hort.
R. M. Pratt, Ph.D., Asso. Ent.-Pathologist W. G. Cowperthwaite, Ph.D., Asst. Hort.
J. W. Davis, B.S.A., Asst. Ent.-Path.
W. A. Simanton, Ph.D., Entomologist
E. J. Deszyck, Ph.D., Asso. Horticulturist
C. D. Leonard, Ph.D., Asso. Horticulturist FIELD LABORATORIES
I. Stewart, M.S., Asst. Biochemist Watermelon, Grape, Pasture-Leesburg
W. T. Long, M.S., Asst. Horticulturist
M. H. Muma, Ph.D., Asst. Entomologist C. C. Helms, Jr., B.S., Asst. Agronomist

EVERGLADES STATION, BELLE GLADE Strawberry-Plant City
R. V. Allison, Ph.D., Vice-Director in Charge A. N. Brooks. Ph.D., Plant Pathologist
Thomas Bregger, Ph.D., Sugar Physiologist
J. W. Randolph, M.S., Agricultural Engr.
W. T. Forsee, Jr., Ph.D., Chemist Vegetables-Hastings
R. W. Kidder, M.S., Asso. Animal Hush. A. H. Eddins, Ph.D., Plant Path. in Char.ge
T. C. Erwin, Assistant Chemist E. N. McCubbin, Ph.D., Horticulturist
C. C. Seale, Asso. Agronomist
N. C. Hayslip, B.S.A., Asso. Entomologist
E. A. Wolf, M.S., Asst. Horticulturist Pecans-Monticello
W. H. Thames, M.S., Asst. Entomologist A. M. Phillips, B.S., Asso. Entomologist
W. N. Stoner, Ph.D., Asst. Plant Path. John R. Large, M.S., Asso. Plant Path.
W. A. Hills, M.S., Asso. Horticulturist
W. G. Genung, B.S.A., Asst. Entomologist
Frank V. Stevenson, M.S., Asso. Plant Path. Frost Forecasting-Lakeland
R. H. Webster, Ph.D., Asst. Agronomist Warren O. Johnson, B.S., Meteorologist 2
Robert J. Allen, Ph.D., Asst. Agronomist
V. E. Green, Ph.D., Asst. Agronomist 1 Head of Department
J. F. Darby, Ph.D., Asst. Plant Path. 2 In cooperation with U. S.
H. L. Chapman, M.S.A., Asst. An. Husb. 3 Cooperative, other divisions, U. of F.
Thos. G. Bowery, Ph.D., Asst. Entomologist 4 On leave.










Effect of Processing upon the Nutritive

Value of Milk as Evaluated with Rats
O. D. ABBOTT, R. B. FRENCH and RUTH O. TOWNSEND 1

In popular literature there has been, and is, considerable
agitation to avoid all processed foods and to obtain foods in as
natural a state as possible. Milk is one of the foods which has
been processed in many ways. It has been pasteurized, evapo-
rated, condensed and sweetened, dried and frozen. Moreover,
modern methods of processing and storage make possible the
serving of fluid milk that varies in age from a few hours to many
days or even months. In many sections daily delivery has been
discontinued and delivery every other day or twice a week
initiated. During the tourist season milk shipped into Florida
is heated prior to shipment and pasteurized by the regular
method after arrival in the state. Dry and evaporated milks
are processed by heat and stored for varying lengths of time.
Since milk is still considered the most important and necessary
single food item, any factor or factors that impair or destroy
its nutritive value should be known. The object of this study
was to determine the effect of processing upon the nutritive
value of milk.
Methods
Experimental Animals.-The effects of processing upon the
nutritive value of milk were evaluated by feeding tests on white
rats. The experimental animals consisted of groups of weanling
rats (21 days of age) with six to the group. These rats were
equated on the basis of initial weight, sex and breeding as
determined by litter. Each feeding test ran from 10 to 13 weeks.
Experimental Diets.-The rations used in these experiments
consisted of two-thirds ground whole wheat and one-third milk,
both computed on the dry basis. The wheat was of the hard
spring type and the milks used were raw and pasteurized, fed
fresh and aged for four days; non-fat milk solids also fed fresh
and aged over the summer months without refrigeration, and
evaporated milk. The fresh fluid milk came from two separate
sources referred to in this publication as Source 1 and Source 2.
Vitamin A and fat were added to diets containing non-fat milk

SRegistered nurse, formerly Assistant in Home Economics.









240
0)
200


o 160

z
-120


I 80
0

"4 40 -
SA B C D A B C D A B C D A C D
I INITIAL 4TH WEEK 8 TH WEEK 13 TH WEEK

Fig. 1.-Weight gains of rats fed for 13 weeks on wheat-milk diets: A, fresh raw fluid milk; B, fresh pasteurized fluid
milk; C, evaporated milk; and D, non-fat milk solids plus fat and vitamin A.







6 Florida Agricultural Experiment Stations

solids to bring these factors up to the level found in whole fluid
milk. The supplementary fats used in these diets were fresh and
slightly rancid cottonseed oil and butter.

Experimental Results
Evaluation of the effects of processing upon the nutritive
value of milk was based upon weight gains, reproduction and
lactation performance and skeletal mineralization and develop-
ment of rats. Four groups of rats were fed for 13 weeks on the
wheat-milk diets. Figure 1 shows graphically the initial weight
and the weights at the 4th, 8th and 13th weeks of these groups.
As judged by weight gains, there were no significant differences
in the nutritive value of fresh raw or pasteurized fluid milk,
evaporated milk or non-fat milk solids supplemented with fat and
vitamin A.
During the course of the experiment several factors became
operative which apparently affected the nutritive value of fresh
and aged raw and pasteurized fluid milk from Source 1 and also
aged non-fat milk solids. For comparison the weight curve of
rats fed raw or pasteurized milk from Source 2 are included in
Figure 2, which shows the effect of these milks on the weight
gains of rats.
It will be noted that at the end of the 4th week there were
only slight differences in weight gains in all five groups. There-
after, the rate of gain of all groups fed milk from the first
source decreased, and as the feeding continued the curves
deflected more to the right until they plateaued. At the end
of the experiment no significant weight differences were found
among the four groups. On the other hand, the weight curve
of rats fed milk from Source 2 did not change direction and, at
the end of 10 weeks, the final weights of these rats were from
50 to 60 grams heavier than those of rats fed milk from Source 1.
In feeding non-fat milk solids as a part of the wheat-milk
diet, two factors appeared to affect the nutritive value of this
diet; one, the age of the non-fat milk solids; the other, the degree
of rancidity of the cottonseed oil. Data presented in Figure 3
show that when aged non-fat milk solids were supplemented
with vitamin A and rancid oil (curve 4) weight gains were
significantly lower than those of rats (curve 3) fed fresh non-fat
milk solids supplemented with vitamin A and an equal amount of
the same oil.







Effect of Processing upon the Nutritive Value of Milk 7

240


220


200-


2) 1 80 -


oI 60- 34
Z 5
z140


"I120-


0oo -





60


0 2 4 6 8 10

"TIME IN WEEKS
Fig. 2.-Detrimental effects of unknown factors on growth curves of rats
fed wheat-milk diets. Source 2 milk: (1) identical curves for rats fed raw
or pasteurized milk. Source 1 milk: curves for rats fed (2) fresh, raw;
(3) aged, raw; (4) fresh, pasteurized; and (5) aged, pasteurized.

It will be noted, however, that when fresh non-fat milk solids
were supplemented with vitamin A and fresh oil (curve 2)
weight gains were approximately the same as those of rats fed a
diet of wheat and fresh fluid milk (curve 1).
The data indicate that the difference in weights of rats
as shown in curves 3 and 4 is due primarily to a decrease in
nutritive value of aged non-fat milk solids and to a lesser







8 Florida Agricultural Experiment Stations

degree to the partial destruction of vitamin A by the rancid oil.
On the other hand, the difference in weight curves of rats fed
fresh non-fat milk solids with fresh oil (curve 2) and those fed
the same diet with rancid oil (curve 3) is due primarily to the
partial destruction of vitamin A.
A comparative study was made also of the nutritive value of
two types of fat, butter and vegetable oil, each being added to

240
2
220-

200


180-


160

Z 4
--140




LU



80


60-

40 I I I I I I
0 2 4 6 8 10 12 13
TI ME IN WEEKS
Fig. 3.-A comparison of weight gains of rats fed the wheat-milk diets
with fresh and aged non-fat milk solids and fresh and rancid vegetable oil:
1, controls fed fresh raw milk; 2, fresh milk solids and fresh oil; 3, fresh
milk solids and rancid oil; and 4, aged milk solids and rancid oil.








Effect of Processing upon the Nutritive Value of Milk 9

the wheat-non-fat milk solid diets. Both diets were supplied
with an optimum amount of vitamin A and both contained the
same percentage of fat (10 percent). Therefore, any significant
variation in weight of rats would be due to differences in the
nutritive value of the fat in the two diets. Results of this
feeding test are presented in Figure 4. The graphs indicate
that when judged by weight there were no significant differences
in the weights of these two groups.

240


220 2


o 200-

< 18o--


CD S16o

Z
140-


S120-


1 00-

80-


60-

40 I I III I I I
0 2 4 6 8 10 12 13
TIME IN WEEKS
Fig. 4.-A comparison of the nutritive value of butter with that of
vegetable oil when supplying the fat in the wheat-non-fat milk solids diet:
1, vegetable oil and 2, butter.







10 Florida Agricultural Experiment Stations

Reproduction.-At the end of 13 weeks the females from each
group fed the four types of milk were put into breeding cages
with a male from their group. The breeding record shows that
healthy litters were produced by all groups within 48 to 62 days.
The lactation performance as judged by weaning weight of the
young at 21 days was satisfactory.
Skeletal Mineralization and Development.-Roentgenograms
of all groups taken at the end of 13 weeks and again at
maturity show that, regardless of the type of milk fed, skeletal
mineralization and development were comparable to those of
rats fed laboratory stock food.

Discussion
In the experiments reported herein no significant nutritive
differences were found between dried, evaporated, raw and
pasteurized milk. The experimental procedures were not de-
signed to measure small differences in critical nutrients in the
milks tested. Results of the experiments give evidence that if
in processing there has been a destruction of the nutritive
qualities of the proteins, vitamins or minerals it was so minor
that under the set-up of these experiments it was not detected.
In this study the nutritive value of milk was affected by
factors unrelated to processing methods. At about the 6th
week the low weight gains made by rats fed raw and pasteurized
milk, fresh and aged from Source 1, as compared with the gains
made by rats fed milk from Source 2 indicated that, since the
wheat fed to all groups was from the same source, some factor
or factors were causing deterioration in milk from Source 1.
At the same time it was noted that while neither the fresh raw
nor pasteurized milk had off flavor or odor, the milk of both
types aged for four days was decidedly disagreeable as to both
taste and odor, and the cream formed an oily lump in the neck
of the bottle. It was noted that while the milk intake of rats
fed fresh milk of either type was not reduced, that of the rats
fed aged milk was reduced from one-third to one-half during the
course of the experiment. At the end of the experimental
period rats fed milk from Source 2 were in excellent condition and
from 50 to 60 grams heavier than those fed milk from Source 1,
which were definitely in poor condition, as shown by rough fur
and a general unkempt condition. What factor or factors
affected the nutritive value of this milk were not determined.







Effect of Processing upon the Nutritive Value of Milk 11

However, the data show that the causative agents were not
destroyed by pasteurization.
The nutritive value of a wheat-non-fat milk solids diet supple-
mented with slightly rancid vegetable oil and vitamin A was
affected by changes which came as the result of aging of the
milk and by partial destruction of vitamin A by the rancid fat.
While the aged milk solids were hard and darker in color than
fresh solids, they had a pleasant odor and taste and were eaten
readily by the rats. It is evident from a comparison of the
weight curve of rats fed aged milk solids and rancid oil with
that of rats fed fresh milk solids and rancid oil that the
deterioration of the milk solids which resulted from aging was
the major factor in causing the low weight gains of that group.
The data indicate that the partial destruction of vitamin A by
the rancid fat was a minor factor, for when the same oil was
incorporated in the diet of rats fed fresh milk solids weight
gains were approximately 55 grams higher than when the aged
solids were fed.
Results of these studies indicate that fresh vegetable oil has
a nutritive value equal to that of butter when fed in the milk-
wheat diet. This finding is in agreement with that of Deuel
et al (1), who reported growth and reproduction over 25 genera-
tions of rats on Sherman's diet B where butterfat was replaced
by margarine fat. The results of this multigeneration test over
a period of 10 years show that hydrogenated vegetable marga-
rine fat has a nutritive value equal to that of butter.

Summary
As judged by weight, reproduction and skeletal mineralization
of rats, no significant differences were found in the nutritive
values of raw or pasteurized milk, evaporated milk, or of non-fat
milk solids supplemented with vitamin A and fat.
The nutritive value of Source 1 milk fed raw or pasteurized,
fresh or aged for four days was affected by factors unrelated
to processing, which caused a decrease in weight gains and other
signs of malnutrition in all four groups of rats. The causative
agents were not determined but it was evident that they were
not destroyed by pasteurization.
As shown by a decrease in weight gains of rats, the nutritive
value of the non-fat milk solids-wheat diet was lowered when
aged milk solids and slightly rancid vegetable oil were fed as a







12 Florida Agricultural Experiment Stations

part of the milk-wheat diet. However, when fresh milk solids
and rancid oil were used, weight gains were larger, but when
fresh milk solids and fresh oil were used, the weight gains were
approximately the same as those made by rats fed fresh raw
milk (Source 2) and wheat.
There were no significant differences in weights of rats when
butter replaced vegetable oil in the non-fat milk-wheat diet.
Regardless of the type of milk fed in the milk-wheat diets,
healthy litters were produced by all groups.
Roentgenograms made at the end of 13 weeks and again at
maturity showed that skeletal development and mineralization
of all rats fed the milk-wheat diets were comparable to those of
rats fed the colony stock diet.


Conclusion
Under the conditions of these experiments and when judged
by weight, reproduction and skeletal development and mineral-
ization of rats, the nutritive value of milk was not affected by
processing.

Reference
1. DEUEL, HARRY J., JR., SAMUEL M. GREENBERG, EVELYN E. SAVAGE and
LUCIEN A. BAVETTA. Studies on the comparative nutritive value of
fats. XIII. Growth and reproduction over 25 generations on Sher-
man Diet B where butterfat was replaced by margarine fat,
including a study of calcium metabolism. Jour. Nutr. 42: 239-
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