Group Title: Bulletin - University of Florida. Agricultural Experiment Station ; 383
Title: Storing frozen cream
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 Material Information
Title: Storing frozen cream a preliminary report
Series Title: Bulletin University of Florida. Agricultural Experiment Station
Physical Description: 24 p. : charts ; 23 cm.
Language: English
Creator: Freeman, T. R ( Theodore Russell ), 1906-
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: 1943
Subject: Cream -- Storage   ( lcsh )
Ice cream, ices, etc   ( lcsh )
Genre: government publication (state, provincial, terriorial, dependent)   ( marcgt )
bibliography   ( marcgt )
non-fiction   ( marcgt )
Bibliography: Bibliography: p. 22-24.
Statement of Responsibility: T.R. Freeman, L.E. Mull, E.L. Fouts.
General Note: Cover title.
 Record Information
Bibliographic ID: UF00026389
Volume ID: VID00001
Source Institution: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: aleph - 000925186
oclc - 18232269
notis - AEN5832
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The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source

site maintained by the Florida
Cooperative Extension Service.

Copyright 2005, Board of Trustees, University
of Florida

Bulletin 383
/4 Bulletin 383



(A Preliminary Report)





Single copies free to Florida residents upon request to

February, 1943

John J. Tigert, M.A., LL.D., President of the
Wilmon Newell, D.Sc., Director3
Harold Mowry, M.S.A., Asso. Director
L. O. Gratz, Ph.D., Asst. Dir., Research
W. M. Fifield, M.S., Asst. Dir., Admin.4
J. Francis Cooper, M.S.A., Editor3
Clyde Beale, A.B.J., Assistant Editor3
Jefferson Thomas, Assistant Editor3
Ida Keeling Cresap, Librarian
Ruby Newhall, Administrative Manager3
K. H. Graham, Business Manager3
Claranelle Alderman, Accountant3

W. E. Stokes, M.S., Agronomist'
W. A. Leukel, Ph.D., Agronomist3
Fred H. Hull, Ph.D., Agronomist
G. E. Ritchey, M.S., Associate2
W. A. Carver, Ph.D., Associate
Roy E. Blaser, M.S., Associate
G. B. Killinger, Ph.D., Associate
Fred A. Clark, B.S.A., Assistant
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, D.V.M., Veterinarian3
L. E. Swanson, D.V.M., Parasitologist4
N. R. Mehrhof, M.Agr., Poultry Husb.3
T. R. Freeman, Ph.D., Asso. in Dairy Mfg.
R. S. Glasscock, Ph.D., Asso. An. Husb.
D. J. Smith, B.S.A., Asst. An. Husb.4
P. T. Dix Arnold, M.S.A., Asst. Dairy Husb.3
G. K. Davis, Ph.D., Tech, in An. Nutrition
S. P. Marshall, M.S., Asst. in An. Nutr.
L. E. Mull, M.S., Asst. in Dairy Tech.4
O. K. Moore, M.S., Asst. Poultry Husb.
C. B. Reeves, B.S., Asst. Dairy Tech.
J. E. Pace, B.S., Asst. An. Hush.
C. V. Noble, Ph.D., Agr. Economist' 3
Zach Savage, M.S.A., Associate
A. H. Spurlock, M.S.A., Associate
Max E. Brunk, M.S., Assistant
Ouida D. Abbott, Ph.D., Home Econ.,
Ruth 0. Townsend, R.N., Assistant
R. B. French, Ph.D., Asso. Chemist
J. R. Watson, A.M., Entomologist'
A N. Tissot, Ph.D., Associate
H. E. Bratley, M.S.A., Assistant
G. H. Blackmon, M.S.A., Horticulturist'
A. L. Stahl, Ph.D., Associate
F. S. Jamison, Ph.D., Truck Hort.
R. J. Wilmot, M.S.A., Asst. Hort.
R. D. Dickey, M.S.A., Asst. Hort.4
J. Carlton Cain, B.S.A., Asst. Hort.4
Victor F. Nettles, M.S.A., Asst. Hort.4
Byron E. Janes. Ph.D., Asst. Hort.
A. L. Kenworthy, M.S., Asst. Hort.
F. S. Lagassee, Ph.D., Asso. Hort.2
II. M. Sell, Ph.D., Asso. Hort.2
W. B. Tisdale, Ph.D., Plant Pathologist' 3
George F. Weber, Ph.D., Plant Path.3
Phares Decker, Ph.D., Asso. Plant Pathologist
Erdman West, M.S., Mycologist
Lillian E. Arnold, M.S., Asst. Botanist
R. V. Allison, Ph.D., Chemist' a
Gaylord M. Volk, M.S., Chemist
F. B. Smith, Ph.D., Microbiologist3
C. E. Bell, Ph.D., Associate Chemist
J. R. Henderson, M.S.A., Soils Technologist
L. H. Rogers, Ph.D., Asso. Biochemist4
Richard A. Carrigan, B.S., Asso. Chemist4
L. E. Ensminger, Ph.D., Asso. Soils Chem.
H. W. Winsor, B.S.A., Assistant Chemist
Geo. D. Thornton, M.S., Asst. Chemist
T. C. Erwin, Assistant Chemist
J. N. Howard, B.S.. Asst. Chemist
R. E. Caldwell, M.S.A., Soil Surveyor4
Olaf C. Olson, B.S., Soil Surveyor4

H. P. Adair, Chairman, Jacksonville
R. H. Gore, Fort Lauderdale
N. B. Jordan, Quincy
T. T. Scott, Live Oak
Thos. W. Bryant, Lakeland
J. T. Diamond, Secretary, Tallasassee
J. D. Warner, M.S., Agronomist in Charge
R. R. Kincaid, Ph.D., Asso. Plant Pathologist
Elliott Whitehurst, B.S.A., Asst. An. Husb.'
W. C. McCormick, B.S.A., Asst. An. Husb.
Jesse Reeves, Asst. Agron., Tobacco
W. H. Chapman, M.S., Asst. Agron.'
Mobile Unit, Monticello
R. W. Wallace, B.S., Asso. Agronomist
Mobile Unit, Milton
J. H. Wallace, M.A., Asso. Agronomist
A. F. Camp, Ph.D., Horticulturist in Charge
V. C. Jamison, Ph.D., Soils Chemist
B. R. Fudge, Ph.D., Associate Chemist
W. L. Thompson, B.S., Associate Ento.
F. F. Cowart, Ph.D., Asso. Horticulturist
J. W. Sites, Ph.D., Asso. Hort.
W. W. Lawless, B.S., Asst. Horticulturist'
R. K. Voorhees, Ph.D.. Asso. Plant Path.
H. O. Sterling, B.S., Asst. Hort.
T. W. Young, Ph.D., Asso. Hort., Coastal
C. R. Stearns, Jr., B.S.A., Chemist
J. R. Neller, Ph.D., Biochemist in Charge
J. W. Wilson, Sc.D., Entomologist
F. D. Stevens, B.S., Sugarcane Agron.
Thomas Bregger, Ph.D., Sugarcane
G. R. Townsend, Ph.D., Plant Pathologist
R. W. Kidder, M.S., Asst. An. Husb.
W. T. Forsee, Ph.D., Asso. Chemist
B. S. Clayton, B.S.C.E., Drainage Eng.'
F. S. Andrews, Ph.D., Asso. Truck Hort.4
Roy A. Bair, Ph.D., Asst. Agron.
E. C. Minnum, M.S., Asst. Truck Hort.
N. C. Hayslip, B.S.A., Asst. Entomologist
Geo. D. Ruehle, Ph.D., Plant Path. in Charge
S. J. Lynch, B.S.A., Asst. Horticulturist
E. M. Andersen, Ph.D., Asst. Hort.
W. F. Ward, M.S., Asst. An. Husb. in Charge2
W. G. Kirk, Ph.D., An. Husb. in Charge
E. M. Hodges, Ph.D., Asso. Agron., Wauchula
Gilbert A. Tucker, B.S.A., Asst. An. Husb.4
R. A. Fulford, B.S.A., Asst. An. Hush.
M. N. Walker, Ph.D., Plant Path. in Charge'
K. W. Loucks, M.S., Asst. Plant Path.
E. E. Hartwig, Ph.D., Asst. Agron. & Path.
Plant City
A. N. Brooks, Ph.D., Plant Pathologist
A. H. Eddins, Ph.D., Plant Pathologist
E. N. McCubbin, Ph.D., Asso. Truck Hort.
S. O. Hill, B.S., Entomologist2 4
A. M. Phillips, B.S., Asst. Entomologist'
R. W. Ruprecht, Ph.D., Chemist in Charge,
Jos. R. Beckenbach, Ph.D., Truck Hort. in
E. G. Kelsheimer, Ph.D., Entomologist
F. T. McLean, Ph.D., Horticulturist
A. L. Harrison, Ph.D., Asso. Plant Path.
David G. Kelbert, Asst. Plant Pathologist
Celery Investigations
Jack Russell, M.S., Asst. Entomologist
E. S. Ellison, Meteorologist2 4
Harry Armstrong, Asso. Meteorologist2
1 Head of Department.
2 In cooperation with U. S.
3 Cooperative, other divisions, U. of F.
SOn leave.

Gift \i-V


Page Page
REVIEW OF LITERATURE .... ... ........... 3 Exclusion of Air .......................... 9
EXPERIMENTAL METHOD ....... ................ 5 Flavor Changes ................................ 10
Processing .... .... ....................... 5 Oxidation-Reduction Potentials .... 12
Analyses ................ ... ........... ...... 6 II. Ice Cream ..................... ... ............. 16
RESULTS AND DISCUSSION ............................. 7 Oxidized Flavor ............................. 16
I. Cream .......................... .............. 7 Processing Methods ...................... 20
Untreated Cream ............................ 7 CONCLUSIONS .......... ... .......................... 21
H om ogenization .... .................... 8 IIIBLIOGRAPHY .. ........ ...... ................ 22
Antioxidants ........... ...................... 9
Each year during the tourist season, which usually extends
from December through March, Florida ice cream manufacturers
import large quantities of cream from other states. Through-
out the summer months, however, these manufacturers are
normally confronted with an accumulating surplus of cream.
A practical method of storing this cream for periods of 6 to 8
months would be valuable to the ice cream industry of this state.
Such a procedure would make it possible to utilize the surplus
cream to better advantage, and also would materially reduce,
if not eliminate, the winter shortage.

Although considerable work has been done on the storage of
frozen cream, as indicated by Dahle's (8)1 review of the litera-
ture, there yet remains some lack of agreement as to its possi-
bilities and as to the most satisfactory method of preparing the
cream for storage. A number of writers have noted seasonal
variations in the stability of milk toward the development of
oxidized flavors. Mattick (22) was one of the first workers
to report the prevalence of this flavor defect during the winter
months. A few years later Brueckner and Guthrie (6) con-
curred in this observation by stating that the oxidized flavors
were "more pronounced and more widespread" during winter
than during summer. Likewise, Trout and Gjessing (27) and
Hening and Dahlberg (17) reported that they observed more
difficulty from the oxidized flavor during the winter months.
Josephson and Dahle (19) have shown recently that metal-
induced oxidized flavor is more troublesome during the winter;
a similar observation was reported by Thurston (25). That
this seasonal trend may be largely due to changes in feeding

Italic figures in parentheses refer to "Bibliography."

Florida Agricultural Experiment Station

conditions has been implied by Dahle (7) and Thurston (25).
Webb and Hileman (28) concluded that "summer milk is able
to resist the development of oxidized flavors even in the presence
of a high oxidation-reduction potential." On the other hand
Guthrie (14) was able to see little difference in the development
of oxidized flavor in milk from summer and winter fed cows.
This latter observation corroborates a previous report by Proks
and Groh (23) to the effect that the tallowy flavor appeared
during the summer as well as in the winter.
Effects of the dairy ration constituents on the susceptibility
of milk to the development of oxidized flavors also have been
the subject of rather widespread investigation. Many contra-
dictory reports have appeared in recent years regarding the
effect of vitamin A and carotene. However, the prevailing
opinion, as reported by Henderson (16), is that carotene and
vitamin A in the ration impart a characteristic to the milk which
makes it more resistant to oxidized flavor development. Work
reported by the Kansas station (21) substantiates this view-
Brown and Dustman (1) and Brown, Vanlandingham and
Weakley (4) reported that feeding high-quality alfalfa hay re-
duced the incidence of oxidized flavor in the milk. In a similar
manner Brown and Thurston (3) observed the beneficial effects
of grass feeding. Garrett, Arnold, and Hartman (11) showed
that legume and grass silages were more desirable in this re-
spect than corn silage, beet pulp, and dried citrus pulp. Green-
bank (13) found that green feed did not always inhibit oxidized
flavor development, but that beneficial effects were generally
noted after the cows were on pasture for 2 to 5 weeks.
Guthrie (15) fed cod liver oil in the ration and observed an
increase in the tendency toward occurrence of oxidized flavor.
As a result of feeding different kinds of vegetable oils, Brown,
Dustman, and Weakley (2) brought about a change in the iodine
number of the butterfat and observed a corresponding variation
in the susceptibility of the latter to the development of oxidized
flavor. Upon feeding potassium iodide to dairy cows, Brown,
Vanlandingham and Weakley (5) noted a reduction in the as-
corbic acid content of the milk, but no change in development of
metal-induced oxidized flavor.
It would seem logical that butterfat produced in Florida might
possess storage characteristics differing from those of butterfat

Storing Frozen Cream

produced in more northern latitudes, inasmuch as the climatic
and feeding conditions which prevail in Florida differ from those
in other sections. No experimental work on cream storage has
been reported, to our knowledge, from stations located in the
Southern states.

While recognizing that the use of frozen cream in ice cream
mixes generally results in a certain amount of "oiling off" of
the fat during the processing of the mix, and that the use of
such cream may be a source of difficulty in obtaining the proper
overrun at the freezer, nevertheless the preliminary investiga-
tion reported here was designed primarily for studying methods
of protecting the flavor of the cream during storage.
Processing.-Three lots of cream produced on successive days
(June 5, 6, and 7, 1941) were used in this experiment. In the
production and handling of the milk from which the cream was
obtained, and in the processing of the cream, special precautions
were taken to reduce to a minimum any possibility of contam-
inating the product with copper or iron from the equipment.
Each lot of cream was divided into 4 sub-lots for the purpose
of comparing various methods of processing. After the cream
was processed it was placed in new, clean tin cans, which then
were hermetically sealed with a hand-operated closing machine.
The canned cream was placed immediately in the ice cream hard-
ening room, where the temperature was maintained at approxi-
mately 0 F. throughout the storage period. At the end of the
storage period an ice cream mix was made from each sub-lot of
cream, using this cream as the only source of fat.
The following outline indicates the methods of processing
which were compared, and the manner in which the cream was
treated in each case:
Fat content: 37%
Added sucrose: None
Added copper: None
Heat treatment: 1750 F. for 10 minutes.
Sub-lot A Control
Sub-lot B Homogenized, 2,000 pounds single stage, at 175 F., fol-
lowing pasteurization.
Sub-lot C Control plus 1.5 p.p.m. Cu 2 added after pasteurization.
Sub-lot D -Same as B, plus 1.5 p.p.m. Cu added after homo-
All added copper was in the form of copper sulfate solution.

Florida Agricultural Experiment Station

Fat content: 31.9%
Added sucrose: 12% (88 lbs. cream + 12 lbs. sucrose).
Added copper: 1.5 p.p.m. Cu 2 after pasteurization.
Heat treatment: 175* F. for 10 minutes.
Sub-lot E Control
Sub-lot F- 1.5% Avenex No. 7 (based on weight of cream).
Sub-lot G--0.1% Avenex concentrate (based on weight of cream).
Sub-lot H--0.003% trypsin (based on weight of cream), added to
cream at approximately 100 F. This temperature
was maintained for 15 minutes, after which the cream
was quickly heated to the pasteurization temperature.

Fat content: 35.2%
Added sucrose: 12% (88 lbs. cream + 12 lbs. sucrose).
Added copper: None
Heat treatment: 175 F. for 10 minutes.
Sub-lot I-- Control
Sub-lot J-0.5% ascorbic acid3 (based on total solids content of
cream), added after cooling cream to 140 F.
Sub-lot K Same as control, except containers were left open.
Sub-lot L Same as K except surface of cream was covered with
layer of ice approximately / inch thick. Ice layer
obtained by pouring distilled water on frozen surface
of cream after one day in storage.
Analyses.-Immediately after separation and before process-
ing a sample of cream from each lot was subjected to pH and
oxidation-reduction potential determinations. Six hours after
processing, the redox test was applied to a sample from each
sub-lot of cream. At the end of each month during the 7-month
storage period each sub-lot of cream was scored for intensity
of oxidized flavor and was analyzed for pH and for redox poten-
tial. The ice cream was scored immediately after hardening and
after being in storage 1, 2, and 4 weeks.
The pH and redox potential measurements were made with a
Leeds and Northrup potentiometer-electrometer No. 7660. Meas-
urements of pH were obtained with a glass electrode, whereas
the redox potential determinations were obtained with bright
platinum foil electrodes. In either case, the reference electrode
consisted of a saturated KCl calomel half-cell. All measure-
ments were made at 250 C. 0.50. Oxidation-reduction potential

SAll added copper was in the form of copper sulfate solution.
3 This product, described as d-gluco ascorbic acid, is no longer available.

Storing Frozen Cream

readings were taken after the platinum electrodes had been in
contact with the cream sample for 4 hours. Each value recorded
is based on the average of the readings obtained with 4 elec-
trodes, the observed potentials being recalculated and recorded
on the basis of the so-called zero potential of the normal hy-
drogen electrode.
All flavor scores recorded, for both cream and ice cream, are
the averages of the independent scores of 3 judges, with the
exception of the cream scores for the first month, which are
the average scores of 2 judges. The identity of all samples was
unknown to the judges at time of scoring. Although the cream
samples were scored on a basis of the intensity of the oxidized
flavor, other obvious flavor defects were noted as a matter of
routine. The following system of notation was employed in con-
nection with the judging of the cream samples:
1. No oxidized flavor 3. Slight oxidized flavor
2. Doubtful 4. Pronounced oxidized flavor
5. Intense oxidized flavor
The ice cream flavor scores are based on the American Dairy
Science Association score card, which allows 45 points for flavor.

The flavor scores for all sub-lots of cream are given in Table 1.
The averages shown in the last column are of no significance
per se. However, it is believed they may be useful in comparing
the various methods of processing, inasmuch as these calculated
values should tend to balance out inconsistencies resulting from
the "human error" in scoring the cream samples.
Untreated Cream.-Two of the 3 lots of cream used in this
study contained control sub-lots which may be termed normal
in that they contained no added copper and received no anti-
oxidative treatment (sub-lots A and I). Of the 14 scoring
made on these 2 sub-lots during 7 months of storage, in only
one instance (A at 3 months) did a sample possess as much
as a "slight" oxidized flavor. These results seem to indicate
that the cream possessed a fairly high degree of natural stability
against the development of oxidized flavor. Although it must
be remembered that an effort was made to avoid metallic con-
tamination during processing, a preliminary study at this station
(10) has shown that milk produced in Florida appears to be

8 Florida Agricultural Experiment Station

Flavor Score

Treatment I

No added sucrose

A Control 1.5 1.7 3.2 2.5 1.3 1.0 2.2 1.9
B Homogenized 1.0i 1.0 1.0 1.75 1.3 1.0 1.3 1.2
I |
C Copper 3.5 3.0 3.0 2.75 2.2 3.2 2.3 2.9
D Copper, 1.5 2.0 2.7 3.0 2.7 3.2 2.5 2.5
12% added sucrose, 1.5 p.p.m. added copper

E Control 3.0 2.8 1.7 3.2 2.7 2.8 3.5 2.8
F Avenex 1.0 1.0 2.3 1.3 1.5 1.2 2.8 1.6
G Avenex 3.0 2.5 2.8 2.8 2.2 2.3 3.0 2.7
H Trypsin 3.75 4.1 2.5 3.0 2.8 2.2 2.8 3.0

12%r added sucrose, no added copper

I Control 1.0 1.7 1.3 1.0 1.3 1.3 1.7 1.3
J Ascorbic acid 1.0 1.3 1.3 1.5 1.3 1.5 1.0 1.3
K Containers 2.5 1.3 1.3 1.5 1.7 2.7 1.8
L Ice layer 1.0 1.3 1.3 2.7 1.7 1.8 2.5 1.8

less susceptible to the development of oxidized flavor than milk
produced in other sections of the United States. Whether or
not these results are representative of the storage qualities of
Florida-produced cream in general remains to be established
through further trials. However, Rogers (24) and Trout (26)
state that by observing proper precautions ice cream of good
quality can be made using, as the only source of fat, cream
which has been stored in the frozen state for as long as a year.
Homogenization.-According to the flavor scores of Lot I,
the value of homogenization as a means of preventing oxidized
flavor development in frozen cream during storage is question-
able. It is interesting to note that homogenization afforded
definite flavor protection for the first 3 or 4 months of the

Storing Frozen Cream

storage period, after which time its effect had apparently be-
come dissipated. This method of treatment was slightly more
effective in the cream which received no added copper.
On the basis of the present study the authors are inclined to
feel that the slight advantage, from the standpoint of flavor,
gained by homogenizing the cream is more than offset by cer-
tain practical disadvantages involved in the processing and
handling of the product. Homogenization increases the cost of
processing, by virtue of the additional time and power required
and the use of an additional piece of equipment. The high vis-
cosity of homogenized cream makes cooling a slow, difficult pro-
cess, and tends to increase waste through the adherence of the
cream to cooler, pipelines, and cans. Furthermore, destabiliza-
tion of the emulsion resulting from the freezing of the cream
was much more pronounced in the 2 sub-lots of homogenized
cream than in the 2 corresponding sub-lots of unhomogenized
cream. This latter observation agrees with those reported in
1936 by Josephson and Dahle (18), and more recently by
Trout (26).
Antioxidants.-Using the average scores in Lot II for com-
parison, one would conclude that avenex, avenex concentrate,
and trypsin rank in that order as antioxidants for cream to be
stored frozen. At the 6-month and 7-month periods, however,
the order of preference is less evident. Excluding the 7-month
score, avenex has antioxidative properties definitely superior to
either avenex concentrate or trypsin. The greatest deteriora-
tion in the flavor of the avenex-protected cream was between
the 6- and 7-month periods of examination. There is little
choice between avenex concentrate and trypsin, regardless of
the age, up to 7 months, of the frozen cream.
It is impossible to judge the efficacy of ascorbic acid as an
antioxidant, inasmuch as the control sample in this lot failed
to develop an oxidized flavor. The commercial use of ascorbic
acid for this purpose is, however, impractical at the present
time because of its high price.4
Exclusion of Air.-In all the comparisons thus far discussed
the containers were hermetically sealed. This probably would

We have since received an experimental quantity of another analogue
of ascorbic acid which is designated as sodium arabo ascorbate. It is
stated that when available for distribution this product will be sufficiently
low in cost to render feasible its use as an antioxidant in milk and cream.
Trials with this preparation are in progress, but results are not yet

Florida Agricultural Experiment Station

be impractical in most ice cream plants. It was deemed im-
portant, therefore, to determine whether or not the "control"
samples were receiving a form of protection which they would
not have under practical conditions. Accordingly, one sub-lot
of cream was stored in cans which were left open. The possible
value of a surface layer of ice as a protective measure also
seemed worth investigating. Results of these comparisons are
indicated in the flavor scores of sub-lots I (control), K, and L.
The average scores indicate only a slight advantage in sealing
the cans, and no improvement resulting from the surface layer
of ice. These comparisons, however, are again of questionable
significance, in view of the fact that none of the cream, includ-
ing the control, developed an oxidized flavor during the storage
period. As the cream in Lot III had no copper added, it appears
that a more severe test is required to yield conclusive informa-
Flavor Changes.-It would logically be suspected that the
flavor of stored cream would become progressively more objec-
tionable as the storage period lengthens. This was by no means
the universal case, however, as is clearly indicated by the data
shown in Table 1. The maximum intensity of oxidized flavor
occurred as frequently during the first half of the storage period
as during the last half. For convenience of observation, this
information is shown in Table 2.
Sub-lot A B C D E F G H I J K L
Age 3 4 1 6 7 7 1 2 2 4 6 4
and 7 and 7 and 6

Greenbank (13) postulated an explanation of the chemical
changes involved when tallowy or oxidized flavors are produced
in milk. He suggested that the tallowy flavor results from the
mild oxidation of some minor constituent of milk, perhaps
lecithin, and that further oxidation of this tallowy-flavored
intermediate substance produces an end product which is free
from tallowiness. These successive changes he represented by
the following hypothetical equation:
R > RO > RO.
(No oxidized flavor) (Oxidized flavor) (No oxidized flavor)
The observations indicated in Table 2 appear to support such
an hypothesis. It might be concluded, for example, that the

Storing Frozen Cream

reaction went to completion early in the storage period in the
cream samples of sub-lots A, B, C, H, and L.
However, a different situation apparently is involved in sub-
lots G and I, wherein the maximum oxidized flavor development
occurred both at the beginning and at the end of the storage
period. It is possible that a second maximum would have oc-
curred in other sub-lots if longer storage periods had been used.
This recurring oxidized flavor, following its previous disappear-
ance, has not been observed in milk, so far as the authors are
aware. Assuming that the reactions take place in accordance
with Greenbank's hypothesis, the Law of Mass Action may pro-
vide a basis of explanation for the observations recorded in
Table 2.
The first stage of the reaction may be represented as follows:
R + 0 RO (a)
(No oxidized flavor) (Oxidized flavor)
in which R represents the "minor constituent" involved. We
may consider that the amount of this constituent in milk is so
small that it is all changed to the oxide, with an appreciable
amount of dissolved oxygen still unused. The second step of
the reaction then proceeds as follows:
RO + 0 -- > RO (b)
(Oxidized flavor) (No oxidized flavor)
The ultimate effect of reaction (b) on the flavor of the milk
would depend entirely upon the supply of oxygen, if the time
element is not considered. With an adequate supply of oxygen,
all oxidized flavor would be removed by virtue of oxidation of
the oxide to the peroxide. If the oxygen supply is inadequate,
a certain degree of oxidized flavor may persist.
Now consider how these reactions might behave in cream
which, for the sake of discussion, may be presumed to contain
a much greater concentration of R. Under such conditions re-
action (a) will be limited by the availability of oxygen rather
than R. Let it be assumed that the supply of readily available
oxygen becomes exhausted when not more than half of R has
been oxidized. Furthermore, an accumulation of the product
RO will tend to slow the reaction. Thus the reaction is greatly
retarded until a new supply of oxygen has had an opportunity
to diffuse from the surface into the container of cream. Obvi-
ously, the rate of diffusion will be very slow through the frozen
cream at the low storage temperature used. After a matter of
weeks or months oxidation again takes place, reaction (b) pro-

Florida Agricultural Experiment Station

ceeds, and the intensity of the oxidized flavor decreases. It will
be recalled, however, that not all of R has been subjected to the
oxidation process. Accordingly, if oxygen once more becomes
available, it may combine with R to produce more of the tallowy-
flavored oxide. This is possible since reaction (b) has removed
enough of the product of reaction (a) to allow the latter again
to proceed.
Although the flavor scores in Table 1 represent degrees of
oxidized flavor only, other noticeable flavor defects were recorded
as a matter of routine. A total of 237 individual flavor examina-
tions were made by the 3 judges on the 12 sub-lots of cream over
the 7-month period. The only flavor criticism other than "oxi-
dized" consistently made by more than one judge was "cooked,"
"heated," or "custard," which criticism was recorded 49 times
during the course of the experiment. It is significant that only
2 of these 49 observations were on cream samples containing
added copper. These results are in keeping with the viewpoint
of other investigators who maintain that the cooked flavor re-
sults from the production of sulfhydryls, and that the latter are
incompatible with copper ions (9, 12, 20).
Oxidation-Reduction Potentials. Data showing oxidation-
reduction potentials of the cream are given in Table 3. Whereas
Dahle, et al (9) reported an increase in Eh 5 during the first
month, followed by a consistent decrease during the remainder
of the storage period, our observations, as recorded in Table 3,
do not show this trend. The present study indicates an increase
in Eh (average of all sub-lots) during the first 4 months, after
which the potential remains fairly constant. This is shown
graphically in Fig. 1.
The data in Table 3 indicate that the protective action ob-
tained from avenex, avenex concentrate, and trypsin is not due
to the effect of these antioxidants on the oxidation-reduction
potential of the cream. Comparing the average potentials (en-
tire storage period) in Lot II, it will be observed that the control
sample had a lower potential than the samples containing the
antioxidants. At the 7-month period, however, the Eh of the
avenex-containing cream was considerably lower than that of
the control sample. As pointed out previously, the oxidized
flavor intensity of the avenex-containing cream showed the
greatest increase between the 6- and 7-month periods of storage.
"Eh is the symbol for redox potential or oxidation-reduction potential,
which is a measure of the oxidizing intensity of a solution.


Lot Sub-lot Treatment Unpro- __Processed
__ cessed Fresh 1 Mo. I 2 Mos. ] 3 Mos. 1 4 Mos. 1 5 Mos. | 6 Mos. 7 Mos. Average
No added sucrose

A Control

B Homogenized
C Copper
C Copper,
D Copper,nized

I Control

J Ascorbic acid

K Containers open

L Ice layer






.1601 .2269 .2388 .3366 .4000 .3320 .3401

.2029 .1990 .2968 .3341 .4114 .3226 .3371

.2662 .3036 .3986 .4296 .4731 .4414 .4608

.2597 .3260 .3314 .4601 .4968 .4544 .4718

12'% added sucrose, 1.5 p.p.m. added copper

.3120 .3074 .3116 .4323 .4349 .4428 .4438

.3446 .3142 -- .4334 .4373 .4151 .4473

.2942 .3227 .4284 .4311 .4262 .4426 .4376

.2938 .3031 .4374 .4364 .4333 .4438 .4288

12% added sucrose, no added copper

.2136 .2400 .3006 .3261 .3357

.1502 .1410 .1540 .1532 .1226

.2136 .2457 .3053 .3243 .3507

.2136 .2265 .2998 .3239 .3513

.2437 .2630 .3184 .3b84 .3894









.3773 .3808 1









.4816 .3958

.4258 .4025

.4591 .4052

.4529 .4037

.3511 .3079

.1874 .1525

-- .3078

.3593 .3110

.3913 ****




Florida Agricultural Experiment Station

The search for a significant relationship between redox poten-
tials and flavor scores has not been particularly fruitful. An
attempt to correlate the 83 flavor scores in Table 1 with the
corresponding redox potentials of Table 3 was unsuccessful, in-
dicating that there is no important relationship between the
degree of oxidized flavor and the oxidation-reduction potential,
when these 2 characteristics are determined simultaneously in
the cream sample.
The value of a test for predicting the keeping quality of stored
cream is obvious. Such a test, to be of practical use to the in-
dustry, must be relatively simple. Although the redox potential
determination does not answer this description, it should be
helpful to have an understanding of any fundamental relation-
ship between changes in redox potential and the development
of oxidized flavors.

... .. ... .. i.. -l-F|,' ,;
I I I... l i

Fig. 1.-Relationship between age of stored cream and oxidation-reduction

Greenbank (13) states that the tendency of a milk sample
to develop oxidized flavors depends upon the degree to which
it is poised. This characteristic of the sample he determined
by measuring the oxidation-reduction potential before and after
the addition of copper. It was hoped that a similar relationship
might be found for cream to be stored frozen, by relating the
change in potential resulting from processing with the subse-
quent development of oxidized flavor. No such relationship was
it i posed.Thi chractrisic f th saplehe dterine
by masurng te oxdaton-rducton pteniabfoead fe
th ditino opr.I a oe ta iiarrltosi
migh be! fon o ra ob soe rzn yrltingth

* :1


:1 I

7 I '

..q. ... ... ..
.- .. -

7 .
-- '' .
:, 1- .9 I
SI i ,p: : I
igk obbu Ii:I;
I T:
;..1: 'I- -,- , i :, ', !t ''
.. ... -'... .. ..

i _i I'
-'li_ < :'"_ .. i --
-.. L i i i, ,r ," '-
Ii -- ,, ,I ..- -- -T-- "
:: -: ,, ,,l 1 ] ; i !

Fig. 2,-Change in Eh as related to flavor score of cream at monthly intervals. The correlation coefficients indicate that
the change in Eh brought about by processing is nA)t a reliable measure of the stability of the cream.

Florida Agricultural Experiment Station

found, however, with the cream used in this experiment. The
change in the Eh of the cream brought about by processing was
of little significance from the standpoint of predicting keeping
quality, as will be noted upon examination of the correlation
coefficients in Fig. 2. For storage periods of less than 7 months
the correlation between change in Eh resulting from processing,
and oxidized flavor, is not significant. A closer relationship was
found between the change in potential during storage and the
intensity of the oxidized flavor at the end of the storage period,
as is indicated by the higher correlation coefficients. However,
this is of theoretical interest only, since it would be of no value
for predicting keeping quality. Fig. 2 shows correlation co-
efficients for storage periods up to 7 months. For the data
involved in this particular case, values below + .665 are not
significant.6 This point is indicated by the horizontal line on
the graph.
Oxidized Flavor.-Inasmuch as frozen cream is stored almost
exclusively for use in ice cream, it is essential to know what
effect this stored cream has on the quality of the finished ice
cream. Data concerning this phase of the experiment are pre-
sented in Table 4. In a general way, the ice cream flavor scores
and criticisms reflect the quality of the cream used. There are
a few notable exceptions, however, which will receive further
discussion in a later paragraph.
It is agreed rather generally that oxidized flavors embrace
the principal flavor defects encountered in cream stored in the
frozen condition (8). This being true, it is important to know
to what extent such flavors will be imparted to ice cream made
from the stored cream. This factor, under commercial condi-
tions, would be given primary consideration in judging to what
extent a given lot of frozen cream could safely be used as a
source of fat in the ice cream mix. These same considerations
will determine the order in which several lots of frozen cream
of different ages should be used.
The data in Table 4 indicate an inverse relationship between
the intensity of the oxidized flavor in the stored cream and the
flavor score of the finished ice cream. This means that to pro-
duce an ice cream of superior flavor one should use stored cream
that possesses little or no oxidized flavor. A statistical treat-
"Student's" method of t was employed for calculating the value + .665.








Flavor of
7 Months

K -

L 2.5

age -

1 Day














Ice Cream Flavor Scor

1 Week I

Criticism Score Criticism

Lacks fine
S1. metallic
S1. lacks fine
S1. oxidized
V. oxidized (2)
V. oxidized (2)
S1. oxidized
Oxidized (2)
Sl. oxidized (2)

Sl. oxidized (3)

S1. oxidized (2)
V. oxidized

Sl. metallic
Sl. cooked
Sl. cooked
Cooked (2)

S1. cooked
Lacks freshness

Sl. cooked

38.2 Lacks fine
flavor (2)

38.8 Lacks fine

33.8 Oxidized (2)
V. oxidized
33.3 Oxidized
V. oxidized (2)
33.7 Oxidized
V. oxidized (2)
34.7 Sl. oxidized
V. oxidized
35.5 Sl. oxidized (2)
36.8 Sl. oxidized (2)

37.8 Sl. oxidized
S1. cooked
36.8 Cooked (3)
Old ingredi-
ent (2)
38.3 Lacks fine
38.8 Lacks fine


es and Criticisms* Loss in
I Score,
2 Weeks 4 Weeks Aver- 4 Wks.
Criticism I Score Criticism age

Sl. oxidized 35.5 Oxidized 37.4 2.7
Lacks fine Old ingredient
flavor (2)
Lacks fine 36.8 Lacks fine 38.0 1.45
flavor (2) flavor
S1. cooked
V. oxidized (3) 33.3 Oxidized (2) 33.7 1.7
V. oxidized
V. oxidized (2) 33.5 Oxidized (2) 33.7 0.5
Old ingredient V. oxidized
























V. oxidized (2)
Sl. oxidized,
V. oxidized (2)

Oxidized (3)

Sl. oxidized
V. oxidized
No criticism

Old ingredient
Sl. lacks fresh-
Sl. cooked
Sl. cooked

When more than one judge recorded the same criticism, this is indicated by an appropriate number in

Criticisms of the three judges are given.
parentheses following the criticism.
V. = very; Sl. = slight.


Sl. oxidized (2)
Sl. oxidized
V. oxidized
Sl. oxidized
V. oxidized (2)
S1. oxidized (2)

Sl. cooked

Cooked (3)
S1. putrid

Lacks fine
Sl. cooked
Sl. cooked (2)
Sl. lacks fine

Florida Agricultural Experiment Station

ment of this correlation, however, does not seem feasible for 2
reasons. In the first place, the samples are not strictly com-
parable, inasmuch as no 2 sub-lots received exactly the same
treatment. In the second place, the cream scores indicate in-
tensity of the oxidized flavor alone, whereas the scores for ice
cream indicate the total effect for all flavors. The following
remarks should, however, aid in a fuller appreciation of the
significant data in Table 4.
A careful consideration of the flavor criticisms shows that
only 2 defects, "oxidized" and "cooked," were important from
the standpoint of frequency. In most cases a score of 36 or
less indicates the presence of oxidized flavor in some degree.
Ice cream samples possessing very pronounced oxidized flavor
were scored 33 to 34, whereas a score of 35 to 36 indicates that
the sample possessed only a slight oxidized flavor. Thus it may
be stated that, with the exception of one sample, ice cream flavor
scores within the range of 33 to 36 mainly indicate varying
degrees of intensity of the oxidized flavor, whereas scores of
37 to 39 are primarily due to differences in the intensity of the
cooked flavor or to other mild off-flavors. The one exception
mentioned is sub-lot J, which contained ascorbic acid. Through-
out the storage period the cream in this sub-lot was criticized
as possessing a very objectionable custard or cooked flavor.
In studying the data in Table 4 it was discovered that 4 sub-
lots, A, C, D, and L, were noticeably inconsistent with the
general trend. Further examination of the data from these 4
sub-lots revealed an interesting relationship among these "ex-
ceptions." To facilitate this observation, the pertinent data are
assembled in Table 5. The 4 sub-lots are grouped into 2 pairs,
according to the degree of oxidized flavor in the cream.

Sub- Cream, 7 Months Ice Cream Scores
lot Copper Antioxidative I
I Added ITreatment Score 1 day 1 wk.2wks.|4wks. Av. I Loss
p.p.m. i
A 0 None | 2.2 38.2 38.2 37.8 35.5 37.4 2.7
C 1.5 None 2.3 35.0 33.8 32.7 33.3 33.7 1.7

D 1.5 Homogenized 2.5 34.0 33.2 33.8 33.5 33.7 0.5
L 0 Ice layer 2.5 39.0 38.8 39.25 37.7 38.7 1.3

Storing Frozen Cream

It should be noted that for both pairs the degree of oxidized
flavor in the 2 cream samples within a pair is practically the
same. Yet, 24 hours after they were frozen the paired ice cream
samples scored 3 to 5 points apart on flavor. In both pairs the
ice cream made from cream to which copper had been added
suffered a great loss in score during the first 24 hours, as com-
pared with the corresponding sample which contained no added
copper. The difference between the scores of the copper-
containing and copper-free samples of ice cream changed rela-
tively little during the 4-week storage period. It is apparent,
therefore, that the greatest injury to the flavor of the ice cream
containing added copper occurred during the processing or freez-
ing of the mix, or during the first day of storage.
The data of Table 5 may serve as the basis for some interesting
and perhaps practical observations, namely: (1) The rapidity
with which oxidized flavors developed was much greater in ice
cream than in cream; (2) certain cream samples which had been
stored in the frozen condition possessed a fairly desirable flavor
but produced ice cream with an objectionable oxidized flavor.
Thus it would seem that in judging the suitability of a certain
lot of stored cream for use as an ingredient in ice cream mix,
flavor alone is not an adequate criterion; one should know also
whether or not the cream has been subject to appreciable copper
The importance of copper as a cause of oxidized flavors in
cream and ice cream is quite apparent. Almost without excep-
tion ice cream criticized for having an oxidized flavor was pre-
pared from cream which had been treated with copper at the
beginning of the storage period. Likewise, all copper-contam-
inated ice cream was criticized as having an oxidized flavor.
Cream which is to be stored for subsequent use in ice cream
should be protected, by every reasonable precaution, from copper
contamination. The exposure of the cream to copper surfaces
during the various stages of processing should be reduced to a
minimum. The addition of an antioxidant to the cream does not
afford absolute protection, as may be observed from the data of
Table 4.
Finally, it should be recalled that in this experiment the frozen
stored cream served as the only source of fat in the ice cream.
In the past this has not been generally recommended as a com-
mercial practice. Most investigators have suggested that not
more than 40 to 60 percent of the fat in an ice cream mix should

Florida Agricultural Experiment Station

be derived from stored frozen cream. It is reasonable to pre-
sume that, had the proportion of frozen cream used in our ex-
perimental ice cream mixes been reduced one-half, the flavor of
several of the ice cream samples would have been improved
materially. In many instances, however, it may be definitely
advantageous for an ice cream plant to use frozen cream as
the sole source of fat, if this may be done without jeopardizing
the flavor of the finished product. The results herein reported
suggest that such a procedure is entirely feasible, provided the
cream is of high quality when placed in storage.
Processing Methods.-Since it has been observed that the
correlation between cream scores and ice cream scores is not
perfect, it would seem logical, when comparing the several
methods of processing the cream for storage, to give the greater
emphasis to the quality of the resulting ice cream.
Homogenization of the cream had a slight beneficial effect, if
the cream was relatively free from copper when placed in stor-
age. This treatment did not improve the flavor of the ice cream
if copper was added to the cream at the time it was placed in
In comparing the antioxidants, if one's judgment is based
on the flavor scores of the ice cream 1 day old, the order of pref-
erence would be avenex, avenex concentrate, and trypsin. It is
interesting to note that the trypsin ice cream scored 0.5 point
lower than the control on the first day, whereas after the ice
cream had been in storage one week the ice cream containing
trypsin scored 3.1 points higher than the control. If the com-
parison of the 3 antioxidants is made on the basis of the average
flavor scores, there is little choice among them, although they
rank in the reverse order of that previously noted.
It is impossible to judge the value of ascorbic acid as an anti-
oxidant, for 2 reasons. First, the control sample of ice cream
failed to develop a definite oxidized flavor. Second, the ascorbic
acid apparently caused an off-flavor to develop in the ice cream
with the result that this ice cream scored more than a point
lower than the control.
Mechanical exclusion of air from the frozen cream, either by
sealing the can or by providing a surface layer of ice, seems to
be of little value. There was little, if any, improvement in the
flavor of ice cream prepared from stored cream "protected" by
these procedures.

Storing Frozen Cream

In summary, an evaluation of the methods of processing the
cream, based on flavor of the ice cream, is in essential agree-
ment with previously drawn conclusions based on flavor scores
of the stored cream.
1. Ice cream of satisfactory quality can be made from cream
which has been stored 7 months at 00 F., provided the cream
is relatively free from copper. Cream may be stored thus with-
out the use of an antioxidant.
2. Homogenization of the cream as a means of preventing
the development of oxidized flavor during storage is of doubtful
value, particularly if the cream is stored longer than 3 or 4
months. Homogenization is more effective if the cream does not
contain appreciable amounts of copper.
3. Avenex (1.5%), avenex concentrate (0.1%), and trypsin
(0.003%) were effective antioxidants in frozen cream stored 7
months. When the frozen cream was used in ice cream the
flavor scores of the latter indicated that the 3 antioxidants were
of about equal value.
4. The effectiveness of added ascorbic acid, hermetic sealing
of the can, or a surface layer of ice as antioxidative treatments
was not established by this experiment, due to the fact that the
control samples failed to develop any oxidized flavors.
5. Apparently the ascorbic acid was a factor contributing to
the production of an objectionable custard-like or cooked flavor
in the cream.
6. Oxidized flavor may reach its maximum intensity in frozen
cream at any period from the first to the seventh month of
7. The cooked flavor resulting from pasteurization was greatly
reduced, usually eliminated, if 1.5 parts per million of copper
was added to the cream following pasteurization. It is not rec-
ommended, however, that copper be added to the cream for this
8. The oxidation-reduction potential in frozen cream increased
during the first 4 months of storage, after which it remained
fairly constant.
9. There is no definite relationship between oxidized flavor
and oxidation-reduction potential in stored cream, when the 2
are determined at the same time.

Florida Agricultural Experiment Station

10. The change in Eh of the cream brought about by process-
ing is of little value for predicting the keeping quality of the
cream when stored in the frozen condition.
11. There is a direct relationship between the change in po-
tential during storage and the intensity of the oxidized flavor
at the end of the storage period.
12. The flavor of stored frozen cream is an important factor
in determining the flavor of ice cream prepared from it. How-
ever, when stored frozen cream is used for ice cream manufac-
ture, the degree of oxidized flavor in the finished ice cream is
not always proportional to the degree of oxidized flavor in the
frozen stored cream.
13. Ice cream prepared from stored frozen cream containing
added copper to the extent of 1.5 p.p.m. will probably develop
an oxidized flavor in less than a week, even though the frozen
cream itself is free of oxidized flavors.
14. Cream which is to be placed in frozen storage should be
produced and handled in such manner as to minimize the danger
of metallic contamination, especially by copper.


1. BROWN, W. C., and R. B. DUSTMAN. Cause and prevention of oxidized
flavor in milk. W. Va. Agr. Expt. Sta. Bien. Rpt. Bul. 298. 1940.
2. BROWN, W. C., R. B. DUSTMAN and C. E. WEAKLEY, JR. Oxidized flavor
in milk. VIII. Effect of degree of saturation of fat in the ration of
the cow upon the iodine number of the butterfat and the susceptibility
of the milk to metal-induced oxidized flavor. Jour. Dairy Sci., 24:
265-275. 1941.
3. BROWN, W. C., and L. M. THURSTON. A review of oxidation in milk
and milk products as related to flavor. Jour. Dairy Sci., 23: 629-
685. 1940.
dized flavor in milk. IX. The effect of the quality of the hay and
early stage of lactation on the carotene content of butterfat and on
the ascorbic acid content of the milk and their relationship to the
development of metal-induced oxidized flavor. Jour. Dairy Sci., 24:
925-935. 1941.
dized flavor in milk. X. The effect of feeding potassium iodine sup-
plements to dairy cows on the carotene content of the butterfat and
on the ascorbic acid content of the milk and the relationship to metal-
induced oxidized flavor. Jour. Dairy Sci., 24: 1035-1039. 1941.

Storing Frozen Cream 23

6. BRUECKNER, H. J., and E. S. GUTHRIE. Another source of "oxidized"
flavors of milk. Internatl. Asso. Milk Dealers, Lab. Sec. Proc., pp.
3-16. 1934.

7. DAHLE, C. D. Tallowy flavor in milk. Pa. Agr. Expt. Sta. Ann. Rpt.,
Bul. 320: 22. 1935.

8. DAHLE, C. D. Frozen cream: A review. Jour. Dairy Sci., 24: 245-264.

9. DAHLE, C. D., R. K. LAWHORN and J. L. BARNHART. The effect of cer-
tain factors on the keeping quality of frozen cream. Proc. Internatl.
Asso. Ice Cream Mfrs., 2: 7-23. 1940.

10. FREEMAN, T. R. Oxidized flavor of milk produced in Florida. Milk
Dealer, 32: 3: 26. 1942.

11. GARRETT, O. F., R. B. ARNOLD and G. H. HARTMAN. Some factors
affecting the stability of certain milk properties. IV. A comparison
of seven different roughages on the color and flavor of milk. Jour.
Dairy Sci., 24: 71-83. 1941.

12. GOULD, I. A. Control of flavor in milk heated to high temperatures.
Milk Dealer, 29: 8: 70. 1940.

13. GREENBANK, G. R. Variation in the oxidation-reduction potential as
a cause for the oxidized flavor in milk. Jour. Dairy Sci., 23: 725-744.

14. GUTHRIE, E. S. The effect of feeding cod liver oil on the goaty and
oxidized flavors, and vitamin C in milk. Jour. Dairy Sci., 22: 415.

15. GUTHRIE, E. S. The effect of feeding cod liver oil on the goaty and
oxidized flavors, and vitamin C in milk. Jour. Dairy Sci., 23: 501-
502. 1940.

16. HENDERSON, J. L. The relation of nutrition of the cow to development
of oxidized flavor in milk. Milk Plant Monthly, 28: 12: 26. 1939.
Abs. in Jour. Dairy Sci., 23: A52. 1940.

17. HENING, J. C., and A. C. DAHLBERG. The flavor of milk as affected by
season, age, and level of feeding dairy cows. Jour. Dairy Sci., 22:
883-888. 1939.

18. JOSEPHSON, D. V., and C. D. DAHLE. The importance of the fat globule
membrane in the freezing of ice cream. Proc. Internatl. Asso. Ice
Cream Mfrs., 2: 100-115. 1936.
19. JOSEPHSON, D. V., and C. D. DAHLE. Preventing oxidized flavor in
milk. Milk Dealer, 30: 11: 29. 1941.

20. JOSEPHSON, D. V., and F. J. DOAN. Observations on cooked flavor in
milk-its source and significance. Milk Dealer, 29: 2: 35. 1939.

Florida Agricultural Experiment Station

21. The effect of feeding vitamin A and carotene to
cows on the flavor and color of their milk. Kans. Agr. Expt. Sta.
Bien. Rpt., 1938-1940, p. 86.

22. MATTICK, A. T. R. Oiliness in milk. Jour. Agr. Sci., 17: 388-391.

23. PROKS, J., and J. GROH. Defective flavor (oily-rancid, tallowy and
bitter) of milk. Le Lait, 15: 370-381. 1935.

24. ROGERS, L. A. Ice cream investigations. U. S. Bur. Dairy Indus. Ann.
Rpt., p. 41. 1941.

25. THURSTON, L. M. Oxidized flavor in milk. Internatl. Asso. Milk Deal-
ers, Lab. Sect. Proc., pp. 121-141. 1935.

26. TROUT, G. M. Freezing cream for storage. Ice Cream Field, 39: 4: 42.

27. TROUT, G. M., and E. C. GJESSING. Ascorbic acid and oxidized flavor
in milk. I. Distribution of ascorbic acid and occurrence of oxidized
flavor in commercial grade A raw, in pasteurized irradiated, and in
pasteurized milk throughout the year. Jour. Dairy Sci., 22: 271-281.

28. WEBB, R. E., and J. L. HILEMAN. The relation of the oxidation-
reduction potential of milk to oxidized flavor. Jour. Dairy Sci., 20:
47-57. 1937.

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