Certain biological factors related to tallowiness in milk and cream, PH Tracy, HA Ruehe, RJ Ramsey

Tags: incubation, development, defect, room temperature, Oxidation-reduction, raw milk, R. J. RAMSEY, contaminated, Cream By P. H. TRACY, H. A. RUEHE, metal contamination, bottled milk, hot milk, Biological Factors, PASTEURIZED MILK, experiment, FRED REUEL Alfalfa Wilt, LLOYD, REDUCTION POTENTIAL, measurements, Sweet Cream, streptococcus lactis, cows' milk, market milk
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Certain Biological Factors Related to Tallowiness in Milk and Cream By P. H. TRACY, R. J. RAMSEY, and H. A. RUEHE University of Illinois AGRICULTURAL EXPERIMENT STATION BULLETIN 389
CONTENTS PAGE
Definition of Tallowiness
579
Relation of Incubation of Milk After Contamination With
Metal to the Development of Tallowiness
581
Relation of Incubation of Milk Previous to Contamination
With Metal to the Development of Tallowiness
582
Variation in Tendency of Milk to Become Tallowy
583
Yeast Cells as a Retarder of Tallowiness
583
The Homogenizer as a Retarder of Tallowiness
584
Incubation of Cream as a Retarder of Tallowiness in Butter 585
Relation of Oxidation-Reduction Potential to the Develop-
ment of Tallowiness
587
Method of Measuring Oxidation-Reduction Potential
588
Oxidation-Reduction Potential of Milk
588
Oxidation-Reduction Potential of Cream
592
Summary
593
Conclusions
594
Literature Cited..
. 595
Urbana, Illinois
April, 1933
Publications in the Bulletin series report the results of investigations made by or sponsored by the Experiment Station
Certain Biological Factors Related to Tallowiness in Milk and Cream By P. H. TRACY, R. J. RAMSEY, and H. A. RUEHE' BOTH producers and distributors have spent considerable effort in improving the bacterial quality of city milk supplies. Thru the adoption of milk grading systems and the establishment of sanitary inspection services the bacterial quality of raw milk has been greatly improved. Coincident with this improvement, however, there has been an increasing tendency for bottled milk to have a tallowy flavor. Tho in most of the instances of this flavor defect brought to the attention of the authors, metal contamination has been found to be an important cause of the difficulty, the present greater occurrence of tallowiness cannot logically be attributed entirely to this cause. There probably is but little more opportunity for metal contamination to occur now than formerly, and as a matter of fact, some of the most troublesome cases of tallowiness have been found to occur in those plants where special efforts were made to reduce the amount of copper and iron contamination to a minimum. This suggests that there is some factor other than those already studied that is related to the development of this off-flavor. In an earlier study Tracy and Ruehe11 * found that tallowiness in market milk was more common in winter than in summer. They also noted that the tallowy flavor developed to a greater extent when the milk containing metallic salts was stored at 40 F. than when stored at 68 F. These observations led to a further study of the problem, the results of which are set forth in this publication. Definition of Tallowiness The confusion in the literature in the matter of flavor nomenclature has made it difficult to correlate the work done on tallowiness in dairy products by the different investigators, both in this country and in Europe. Tallowiness has been described in various ways, possibly because of the different degrees of development that may occur. Such terms as oily, cappy, papery, astringent, and metallic have been used. Tallowiness is recognized as a defect due to the oxidation of the butter fat. Not only is the oxidized fat flavor modified by the intermediate 'P. H. TRACY, Associate Chief in Dairy Manufactures, R. J. RAMSEY, Assistant in Dairy Manufactures, and H. A. RUEHE, Chief in Dairy Manufactures.
580
BULLETIN No. 389
[April,
and end products formed, but it is also influenced by the presence of
certain metallic salts which may be detected by taste before the true
tallowy flavor is evident. This fact undoubtedly has led to the use of
different terms in the description of this defect.
Flavors caused by fat oxidation should not be confused with those
flavors, commonly called rancid, that are brought about thru fat hy-
drolysis. It is evident from studies conducted by the authors that the
reaction responsible for hydrolysis is progressive, intermediate
products being formed that give different taste reactions. Samples of raw milk having a normal flavor when freshly drawn from the udder
may sometimes acquire a "cowy" taste upon storage. This defect
later develops into the characteristic rancid flavor and finally reaches
a degree of development in which a soapy flavor predominates. Oxi-
dation-reduction potential measurements indicate that oxidation plays
no part in the formation of these flavors. That the reaction is hydroly-
sis is suggested by the increase in titratable acidity that occurs simul-
taneously with the development of the flavor. Milk evidently contains
an enzyme or other substance responsible for the reaction, since heat-
ing the milk to 142 F. renders the agent inactive. Homogenizing the
raw milk at low temperatures (90-100 F.) hastens the reaction and
intensifies the defect, possibly because in the homogenized milk a
greater fat surface is exposed to the agent responsible for the hydroly-
sis. Furthermore, an antagonistic reaction between the agents of tal-
lowiness and rancidity in raw milk containing copper salts has been shown to exist. This antagonistic reaction makes it necessary in flavor
studies to pasteurize samples of milk and cream so as to destroy the
cause for rancidity in order to produce a tallowy flavor.
Another flavor defect that may be confused with tallowiness is the
flavor caused by the action of sunlight upon milk proteins. Tracy and Ruehe11 * have shown that a short-time exposure of milk in uncolored
glass bottles to sunlight will result in the characteristic tallowy flavor. As the time of exposure of the milk to sunlight is increased, however,
a point is eventually reached where the tallowy flavor is overshadowed
by a burnt flavor. Metallic salts are not a factor in this reaction. Skim
milk and low- fat milks develop more pronounced burnt flavors than
whole milks or cream. Tracy and Ramsey10 * have studied a similar
A flavor defect in cottage cheese.
disagreeable burnt flavor was shown
to result from the exposure of cottage cheese in uncolored glass con-
tainers to either direct or indirect sunlight, the flavor being more pro-
nounced in the curd exposed to direct sunlight. The defect was not
so highly developed in the creamed curd as in the plain curd. The
1933]
TALLOWINESS IN MILK AND CREAM
581
occurrence of a more pronounced flavor in the plain curd is contrary to the result expected if the flavor were due to the oxidation of butter- fat. In the production of tallowiness oleic acid is thought to be the main constituent concerned. This unsaturated fatty acid has the ability to combine with oxygen to produce aldehydes and acids, some of which have the characteristic tallowy flavor and odor. The butterfat does not become oxidized immediately but passes thru an induction period during which there is practically no absorption of oxygen. The duration of this period depends upon such factors as the amount of oxygen present, heat, light, acidity, and the presence of certain metals such as copper and iron. It thus becomes apparent that the problem of tal- lowiness in dairy products is related to those procedures which may affect the length of the induction period that precedes the rapid ab- sorption of oxygen by the fat. The term tallowiness will be used in this bulletin to refer only to those flavors that result from such reactions.
Relation of Incubation of Milk After Contamination With Metal to the Development of Tallowiness When tallowiness occurs in market milk, the first milk thru the system usually has the most noticeable off-flavor, which is undoubtedly due to the fact that the soluble metal oxids which form on the plant
TABLE 1. INCUBATION OF PASTEURIZED MILK AS A RETARDER OF TALLOWINESS
Milk held at
582
BULLETIN No. 389
[April,
held at 40 F. for 24 hours, will become tallowy, whereas a companion sample held at room temperature two or three hours and then placed at 40 F. will have little or no tallowiness 24 hours later. Representative data are given in Table 1. The milk used was the first of a day's run (200 gallons) bottled at the University creamery. Raw milk to which a copper salt had been added was found to respond to incubation in the same way as pasteurized milk.
Relation of Incubation of Milk Previous to Contamination
With Metal to the Development of Tallowiness
As previously mentioned, a tallowy flavor in pasteurized University milk was not noticeable in the summer but was usually pronounced during the winter. This was particularly true of the first milk run thru Benedict nickel internal tubular coolers. This condition was par-
tially corrected by eliminating the Benedict nickel coolers and passing the hot milk over a new tinned copper surface cooler. However, even
in this case, enough metal was apparently added by passage of the milk
thru sanitary pipe lines and thru a bronze piston pump to cause the first milk bottled during cool weather to acquire a distinct tallowy flavor after being held at 40 F. for 24 hours. The defect was much worse during extremely cold weather. With the return of milder outdoor temperatures, the tallowy flavor would be less noticeable and with the arrival of warm weather would disappear entirely. In the fall, however, the trouble would recur. The apparent correlation between climatic conditions and the oc-
currence of tallowiness suggested a relation between the extent of
Biological activity in the raw milk and the tendency of the bottled
product to become tallowy.
2* Davies,
working
independently
in
Eng-
land, has also come to the conclusion that bacteria are a factor in pre-
venting tallowiness, for he states "conditions favoring the develop- ment of taint are low temperature of storage and low bacterial count." Kende7 * believes "oiliness" of whole milk is caused by an oxidizing enzyme in the milk. He also has found that microorganisms will
counteract the oxidation reaction, and he advances the theory that a "factor" is formed in the milk which has the power to counteract the action of the enzyme. The theory that bacteria when present reduce the tendency of the milk to become tallowy is further substantiated by the fact that tallowiness seems to be most prevalent in the milk sold by those distributors who are able to control the bacterial quality of their milk from the time of its production until bottled.
In order to determine whether incubation of the milk previous to
metal contamination might be a factor in the retardation of tallowiness,
1933]
TALLOWINESS IN MILK AND CREAM
583
a series of experiments was performed by the authors, representative results from which are given in Table 2. The incubation of raw milk previous to contamination with metal proved to be a very important factor in retarding tallowiness. In some cases of incubation the increase in numbers of bacteria, as determined by the plate count, was very slight, yet the retarding effect upon fat oxidation was marked.
TABLE 2. RELATION OF INCUBATION OF MILK PREVIOUS TO METAL CONTAMINATION TO DEVELOPMENT OF TALLOWY FLAVOR
Treatment of millc*
584
BULLETIN No. 389
[April,
A heavy suspension of yeast cells was prepared by using Fleishman's yeast cake and distilled water. The suspension was then added to milk in the manner indicated in Table 3.
TABLE 3. EFFECT OF YEAST CELLS ON DEVELOPMENT OF TALLOWY FLAVOR IN MILK
Method of preparing sample"
1933]
TALLOWINESS IN MILK AND CREAM
585
remained free from tallowiness after 24 hours of incubation altho both the control milk and that to which the copper was added and which was passed thru the machine without pressure were strongly tallowy. This effect of the homogenizer is thought to be apparent rather than actual. Homogenization changes the physical consistency of the milk, which may affect the taste. When varying amounts of gelatin were added to milk that was contaminated with copper, the degree of tal-
TABLE 4. EFFECT OF HOMOGENIZATION ON DEVELOPMENT OF TALLOWY FLAVOR IN MILK
Treatment
586
BULLETIN No. 389
[April,
weighed and sampled, is usually stored at 40 F. in 10-gallon milk cans for one to three days before being prepared for churning. On several occasions churnings composed almost entirely of sweet cream have been found to produce a butter having the characteristic fat- oxidized flavor. To determine whether incubation of the cream might be a factor in preventing the flavor defect, the writers arranged to have the cream as it was received from the farmers and the surplus pasteurized cream dumped daily into a glass-lined forewarming vat. The cream was kept at room temperature until enough had been received to make a churning. This usually meant storage of the cream for one to three days. With this change of procedure a marked improvement in the quality of butter was noted. For a period of several weeks during the winter this practice of mixing the creams and holding them at room temperature for one to three days was continued, with a resulting improvement in the butter score from the usual 89-90 to as high as 92. As a result of this practical demonstration of the beneficial effect (from the standpoint of avoiding metallic and tallowy flavors in the butter) of incubating cream to be churned, a series of experiments was conducted under controlled conditions to determine to what extent biological activity in the cream may aid in preventing tallowiness in butter. In these experiments 40-percent cream direct from the separator was cooled to 70 F. and 2.6 parts per million of soluble copper was added. The cream was placed in five glass milk bottles. One bottle was stored at 40 F. and the remaining four bottles were placed at 68 F. At the end of the first day and each succeeding day one bottle was removed from the 68 F. incubator to the 40 F. refrigerator. At the end of five days all the incubated samples were standardized to .3 percent acidity and all lots were pasteurized in the bottles by heating to 142 F. for 30 minutes. After cooling, the samples were stored over night and churned. With the above differences in treatment there was a marked differ- ence in the flavor of the creams and a similar difference in the flavor of the butters. The data in Table 5 are representative of the results obtained. The butter made from cream stored continuously at 40 F. was by far the poorest in flavor, being very tallowy. It was evident that excess incubation would also cause a tallowy flavor to occur in the butter. Sometimes one-day incubation was insufficient, whereas holding the cream at about 70 F. for two days prevented the tallowy flavor from occurring in the fresh butter. It should not be construed from the above findings that proper
1933]
TALLOWINESS IN MILK AND CREAM
587
cooling and storing of cream to be made into butter is of no value. As a matter of fact, the incubation of cream when the cream was not contaminated with metal was of no benefit. The data, however, do offer a possible explanation for the fact that practical buttermakers often have difficulty, particularly in the winter or during cool weather,
TABLE 5. EFFECT OF INCUBATION OF CREAM ON DEVELOPMENT OF TALLOWY FLAVOR IN BUTTER
Cream held at
588
BULLETIN No. 389
[April,
Thornton
and
9* Hastings
have
reported
that
milk
has
reducing
proper-
ties as it comes from the udder, and Skar8 * has suggested that the
leucocytes may play an important role in causing a reducing potential. The part that these cells play in the reducing of milk in the reductase test is well known. Coulter1 * has observed the reducing properties of
sterile bouillon and ascribes this to a removal of molecular oxygen.
Bacteria differ widely in their ability to induce low reducing potentials. Hewitt6 * believes that this ability depends upon the ease with which the organisms form peroxid and catalase. Peroxid-forming organisms such as pneumococci and haemolytic streptococci are not able to induce extremely low potentials. The formation of catalase, accord-
ing to Hewitt, prevents the complete dying off of organisms which
results from the formation of peroxids, thus maintaining a reducing potential. Frazier and Whittier4 * have studied the effect of various
pure cultures on the oxidation-reduction potential of milk. They found
that each organism produced potentials characteristic of that particu-
lar species.
In
another
5* study
they
found
that
Escherichia
coli,
Es-
cherichia communior, and Aerobacter arogenes when grown with
streptococcus lactis, all exerted a restraining influence upon the rapid drop in Eh values usually caused by pure cultures of streptococcus
lactis.
Method of Measuring Oxidation-Reduction Potential To determine to what extent the oxidation-potential reading of milk might be correlated with certain flavor changes, a series of experiments was performed to study the significance of those factors already found to be related to the development of tallowiness. The potentials were determined by observing the E.M.F. exerted on bright platinum electrodes, using a saturated KC1 calomel cell as the reference electrode. The burnished platinum foil electrodes were one centimeter square and .003 inch thick. Connections were made from the reference electrode to the samples under measurement by means of a saturated KC1 liquid junction and saturated KC1 agar bridges. Potential readings were reduced to the conventional hydro- A K gen scale. Leeds and Northrup Type potentiometer and a sensi- tive galvanometer were used to measure the E.M.F.
Oxidation-Reduction Potential of Milk The variation in the oxidation-reduction potential of milk subjected to certain conditions previously found to affect the development of tallowiness is shown in the data in Tables 6, 7, and 8. In Table 6 are the measurements taken on mixed cows' milk of
1933]
TALLOWINESS IN* MILK AND CREAM
589
the University herd. In comparing the Eh value of the milk held at 70 F. for 5 hours, and then stored at 40 F., with the measurements made of some of the same milk held at 40 F. continuously, it will be noted that the reading on milk held at 40 F. continuously changed
TABLE 6. OXIDATION-REDUCTION POTENTIAL OF MIXED Cows' MILK
Time elapsing after setting sample
590
BULLETIN No. 389
[April.
expected to stop bacterial reproduction. This offers a possible expla- nation for the great difference between the tendency of summer milk and winter milk to become tallowy. The data in Table 7 show rather conclusively that the rapid development of a tallowy flavor in milk may be brought about by the
TABLE 7. OXIDATION-REDUCTION POTENTIAL OF MILK FROM AN INDIVIDUAL Cow
1933]
TALLOWINESS IN MILK AND CREAM
591
TABLE 8. EFFECT OF YEAST ON THE OXIDATION-REDUCTION POTENTIAL OF RAW MILK
Time elapsing after setting sample
592
BULLETIN No. 389
[April,
Oxidation-Reduction Potential of Cream As previously noted, incubation of cream contaminated with metal at temperatures high enough to permit bacterial growth was found to improve the flavor of butter made from the cream as compared with the flavor of butter made from some of the same cream stored at 40 F. Eh measurements of such cream revealed much the same situation as exists in the case of milk (Table 10). With incubated cream,
TABLE 10. OXIDATION- REDUCTION POTENTIAL OF RAW CREAMS CONTAINING 35 PERCENT BUTTERFAT
Time elapsing after setting sample
1933]
TALLOWINESS IN MILK AND CREAM
593
Summary Data presented in this study show that milk contaminated with a copper salt is more likely to become tallowy if stored immediately at 40 F. than if held at higher temperatures (68 -90 F.) for 1 to 6 hours before being placed at 40 F. It was also found that milk incubated previous to contamination with metal is less likely to become tallowy than milk cooled immediately to 40 F. after being drawn from the udder of the cow. Milks from individual cows differed in their tendency to become tallowy. This difference is thought to have been due to cells or other antioxidizing substances contained in the milk. Living yeast cells retarded the development of tallowiness in milk stored at 40 F. Dead cells or the filtrate of a yeast suspension had no such effect. Homogenization was found to retard the development of a tallowy flavor in milk. This retardation is thought to have been due to certain physical change in the milk which made it less possible for the judge to detect the development of tallowiness organoleptically. Incubation of cream to which copper had been added raised the score of the butter 3.5 points. Holding the cream at room temperature for one to two days resulted in a butter free from tallowiness, while the butter made from cream stored at 40 F. was very tallowy. Oxidation-reduction studies showed a normal tendency toward reduction in freshly drawn milk. Upon the introduction of copper the potential was found to move toward the side of oxidation. Incubation of the milk usually caused a rapid drop in potential. Yeast cells likewise caused a reduction in potential. Eh values of cream showed much the same effect of metal and temperature variables as Eh values of milk. It is evident that oxidation-reduction potentials are related to fat oxidation in dairy products. Bacteria and yeast result in a change of potential towards the reduction phase, which suggests that a removal of oxygen occurs thru the metabolism process of the organisms. This undoubtedly explains why milk of very good quality, from a bacterial standpoint, is more likely to become tallowy than is milk more highly contaminated. Winter milk, especially that from certified dairies and other careful producers, may be expected to become tallowy readily when contaminated with copper salts.
594
BULLETIN No. 389
[April,
Conclusions 1. Incubation of milk contaminated with copper at 68-90 F. retards the development of tallowiness which normally occurs in such milk stored at 40 F. 2. Incubation of milk at 68-90 F. previous to contamination with copper retards the development of tallowiness. 3. Growth of bacteria in milk will retard the development of tallowiness. 4. Yeast cells will retard the development of tallowiness in milk stored at 40 F. 5. Milks differ in their tendency to become tallowy. 6. Homogenization of milk contaminated with copper causes the tallowy flavor to be less apparent. 7. Incubation of cream contaminated with copper greatly re- duces the degree of tallowiness in the butter. As much as 3.5 points difference in the score of butter may be effected by ripening metalcontaminated cream one or two days before churning. 8. Oxidation-reduction measurements on milk show that: a . Aseptically drawn milk will develop a lower Eh reading upon storage at either 40 F. or room temperature. b. The addition of a copper salt will cause the potential to rise rapidly toward the oxidation phase. c. Bacteria or yeast cells cause a rapid reduction to take place in the milk. 9. Oxidation-reduction measurements on cream show the same general effects of metal contamination and incubation as in the case of milk. 10. The metabolism of bacteria and yeast cells in dairy products plays an important part in the control of tallowy flavors. The effect is probably that of oxygen removal. 11. Bacterial metabolism in the raw milk probably accounts for the general absence of tallowy flavors in pasteurized milk produced during the summer months. 12. Lack of bacterial metabolism in raw milk probably accounts for the tendency for some pasteurized milk to become tallowy during the winter, especially in the case of those dairies that are able to control the quality of their milk from the time of production until it is placed in the bottle.
1933]
TALLOWINESS IN MILK AND CREAM
595
13. Lack of bacterial metabolism in the surplus sweet cream of milk plants and ice-cream plants during the winter months is probably the reason this cream, when churned, often produces a butter with a metallic, tallowy flavor.
Literature Cited
1. COULTER, C. B. Oxidation-reduction equilibria in biological systems. I. Reduction potentials of sterile culture bouillon. Jour. Gen. Physiol. 12, 139-146. 1928.
2. DAVIES, W. L. The action of strong sunlight on milk. Certified Milk 6,
No. 61, 4-5. 1931.
3. DAVIS, J. G. The oxidation-reduction potentials of ripening cheddar cheese. Jour. Dairy Res. 3, 241-253. 1932.
4. FRAZIER, W. C., and WHITTIER, E. O. Studies on the influence of bacteria
on the oxidation-reduction potential of milk. I. Influence of pure cul-
tures of milk organisms. Jour. Bact. 21, 239-251. 1931.
5. -
Studies on the influence of bacteria on the oxida-
tion-reduction potential of milk. II. Influence of associated cultures of milk organisms. Jour. Bact. 21, 253-262. 1931.
6. HEWITT, L. F. XXIII. Oxidation-reduction potentials of pneumococcus cultures. II. Effect of catalase. Biochem. Jour. 25, 169-176. 1931.
7. KEXDE, SIGMUND. Reasons for and combating of "oily" milk defects ("Olei- nase," a new enzyme in the milk). Internat. Dairy Cong. Paper No. 137 (Summary), Section 3, Supplement, p. 55. 1931.
8. SKAR, OLAV. Verhalten der Leukozyten der Milch bei der MethylenblauReduktaseprobe. Ztschr. Fleisch u. Milchhyg. 23, 442-447. 1913.
9. THORNTON, H. R., and HASTINGS, E. G. Studies on oxidation-reduction in milk. I. Oxidation-reduction potentials and the mechanism of reduction. Jour. Bact. 18, 293-318. 1929.
10. TRACY, P. H., and RAMSEY, R. J. Sunlight develops off-flavors in cottage
cheese. Milk Dealer 21, No. 8, 48. 1932.
11. -
and RUEHE, H. A. The relation of certain plant processes to
flavor development in market milk. Jour. Dairy Sci. 14, 250-267. 1931.
AUTHOR INDEX
597
AUTHOR INDEX
1. ANDERSON, H. \V., and KADOW,
K. J. Anthracnose and Gray
Bark of Red Raspberries. .281-292
2. ASHBY, R. C. Shrinkage of Hogs
From Farm to Market by
Truck and by Rail
557-576
3. ASHBY, R. C. See NORTON 16
4. BAUER, F. C. Crop Yields From
Illinois Soil Experiment Fields
in 1931
225-280
5. BURLISON, \V. L. See STEWART 21
6. DORSEY, M. J. and POTTER, J. S. A Study of the Structure of the
Skin and Pubescence of the
Peach in Relation to Brushing 405-424 7. JONES, FRED REUEL See KOEHLER 9
8. KADOW, K. J. See ANDERSON 1 9. KOEHLER, BENJAMIN, and JONES, FRED REUEL Alfalfa Wilt as
Influenced by Soil Tempera-
ture and Soil Moisture
37-80
10. LEWIS, E. P. See LLOYD 1 1
11. LLOYD, J. W., and LEWIS, E. P.
Fertilizer Experiments With
Ten Market-Garden Crops in
Cook County, Illinois
1-36
12. LLOYD, J. W., and NEWELL, H.
M. Causes of Damage to
fruits and vegetables During
Shipment
81-120
13. LLOYD, J. W. See NEWELL 14 14. NEWELL, H. M., and LLOYD, J. W. Air Circulation and Tem-
perature Conditions in Refrigerated Carloads of Fruit . . 157-224 15. NEWELL, H. M. See LLOYD 12
16. NORTON, L. J., and ASHBY, R. C. Price Differences Between Four
Hog Markets Used by Illinois
Stockmen
121-156
17. NORTON, L. J. See STEWART 21
18. POTTER, J. S. See DORSEY 6
19. RAMSEY, R. J. See TRACY 23
20. RUEHE, H. A. See TRACY 23
21. STEWART, C. L.; BURLISON, W.
L.; NORTON, L. J.; and WHALIN,
O. L. Supply and Marketing
of Soybeans and Soybean Pro-
ducts
425-544
22. TRACY, P. H. How to Make
Honey-Cream, a Mixture of
High-Test Sweet Cream and
Extracted Honey
545-556
23. TRACY, P. H.; RAMSEY, R. J.; and RUEHE, H. A. Certain
Biological Factors Related to Tallowiness in Milk and Cream
577-596
24. WHALIN, O. L. See STEWART 21 25. WOODWORTH, C. M. Genetics
and Breeding in the Improve-
ment of the Soybean
293-404
598
INDEX
INDEX
Air circulation in refrigerated fruit
cars, experiments on
157-224
See Contents
158
Aledo experiment field yields. . .246-247
Alfalfa, growth of, influence of soil
moisture
59-61
of soil temperature
48-53
roots, Chemical Composition of. . 72-74
development of wilt bacteria in
68-71
modifications in structure of. .62-68
Alfalfa wilt, characteristics of
39-40
influence of soil temperature and
soil moisture on development
of
37-79
Anthracnose of red raspberries. .281-292 See also Gray bark
Antioch experiment field yields. . . . 247
Apples, tests with refrigerated trans-
portation
170-197
Beans, fertilizer experiments with . .
17-21,33-36
Beets, fertilizer experiments with. . .
13-15,33-36
Bloomington experiment field yields 247
Butter, tallowy flavor in, effect of incubation of cream on . . . .585-587
Carlinville experiment field yields. . 248-249
Carthage experiment field yields. 249-251 Carrots, fertilizer experiments with .28-29,33-36
Cauliflower, fertilizer experiments
with
31-36
Chicago hog market, prices compared
with East St. Louis, Indianap-
olis, and Cincinnati
127-147, 153-154
Cincinnati hog market, prices com-
pared with Chicago, East St.
Louis, and Indianapolis
128-134, 147-150, 153-154
Clayton experiment field yields. .251-252
Cream, high-test, use in making
honey -cream
547-552
Cream, tallowy flavor in
578-595
Crop increases from soil treatments,
net value of
240-241
Crop quality, influence of soil treat-
ment on
242-244
Crop residues, value of in soil treat-
ment
233-234
See also Index. .
. 245
crop rotations ending in 1931, sum-
mary of results of on experiment
fields
230-245
Crop yields on experiment fields in
1931
227-229,246-278
Dixon experiment field yields. . .252-253
East St. Louis hog market, prices compared with Chicago, Indianapolis, and Cincinnati
127-150, 153-154 Elizabethtown experiment field ....
yields
253
Enfield experiment field yields
254
Ewing experiment field yields. . . 255-257
Farm scales, accuracy of
561, 564
Fertilizers, organic manures, index to tables showing results from .... 245
mineral, index to tables showing
results from
244-245
Fruit, air circulation and tempera-
ture conditions in refrigerated
carloads of
158-224
causes of damage to during ship-
ment
81-119
Fertilizers, experiments with on market-garden crops in Cook county
1-36
Gray bark, disease of red raspberries 281-292
control
291-292
history symptoms
283 284-291
Hartsburg experiment field yields. . 257-258
Hog markets, price differences be-
tween
122-154
Hog prices, methods of reducing inter-market variations. . . . 151-153
Hogs, shrinkage of from farm to mar-
ket, comparison of by truck and
by rail
557-576
effect of feeding on
566-573
effect of method of handling on
565-570
Honey, use of in honey-cream
547,551-556
Honey-cream, description flavoring keeping qualities manufacture
547, 555 553 553-555 546-555
packaging use. .
552 . 555
INDEX
599
Indianapolis hog market, prices compared with Chicago, East St. Louis, and Cincinnati
127-134, 143-150, 153-154 Joliet experiment field yields.. . .258-260 Kewanee experiment field yields. 259-261 LaMoille experiment field yields. 261-262 Lebanon experiment field yields. 262-264 Lettuce, fertilizer experiments with
10-13,33-36
Limestone, as vegetable fertilizer. . .6-36 importance of in soil treatment. . 234-237
See also Index
244
Livestock, shrinkage of during ship-
ment
558-576
McNabb experiment field yields.. . . 265
Manchuria, production of soybeans
in
429^30,537,544
Manure, as vegetable fertilizer
6-36
variable response to
231-233
See also Index
245
Marketing, fruit, investigations of
refrigerated transportation. 159-224
fruits and vegetables, experiments
with
83-119
hogs, by truck and by rail .... 558-576
Markets, hog, factors influencing
choice of
124-127
price differences between. . . 122-154
Milk, effect of sunlight on flavor . 580-581
rancid flavor in
580-581
tallowy flavor in
578-595
Minonk experiment field yields. . . . 265
Morrow plots, yields on (1931)
278
Mt. Morris experiment field yields
266-267
Newton experiment field yields. .267-268
Nitrogen, as vegetable fertilizer. . . .8-36
See also Index
244
Oblong experiment field yields. .269-270
Odin experiment field yields. . . .269-271
Oquawka experiment field yields. . . 271
Paint, use ot soybean oil in
463-466
Palestine experiment field yields. 271-273
Peaches, brushing of
418-424
effect on keeping quality. . .422-424
effect on peach hairs
419-422
effect on skin
419
study of skin structure and pubescence in relation to brushing. . 405-124
tests with refrigerated transpor-
tation of
197-213
Peas, fertilizer experiments with. . .
...15-17,33-36
Peppers, fertilizer experiments with 25-27, 33-36 Phosphates, as vegetable fertilizers. . 6-36 Phosphorus, need for by some soils 237-239
See also Index. .
. 244
See also Phosphates
Phytomonas insidiosum
40
See also Alfalfa wilt
Plectodiscella veneta, causal fungus of
anthracnose
286-290
See also Gray bark
Potash, as vegetable fertilizer
6-36
importance in soil treatment
239
See also I ndex
245
Potatoes, fertilizer experiments with
29-31,33-36
Price differences between four hog
markets used by Illinois stock-
men
121-154
Prices, farm products, reasons for
variability in
150-151
Prices, hog, methods of reducing
intermarket variation
151-153
Pubescence of the peach, study of in
relation to brushing
406-424
Rail, use of in hog marketing. . .558-576
Raleigh experiment field yields
272
Rancidity in honey-cream, preven-
tion of
554-555
Raspberries, anthracnose and gray
bark of
282-292
Separator, cream, use in manufac-
ture of honey-cream
547-551
Shrinkage of hogs during shipment,
comparison of by truck and by
rail
.558-576
Soil, systems of treatment on Illinois
fields
....230-245
Soil experiment fields, crop yields
from in 1931
246-278, 227-229
Soils, variation in natural produc-
tivity
230-231
Soybean breeding, experiments with
295-404
improvement of oil and protein
content
357-371
quality of oil. . resistance to disease
371-373 373-377
yield of seed inheritance in
377-399 305-335
genes, list of plant characters linked characters
333-334 323-333 334-336
seed characters
305-323
method of reproduction
300-304
methods of breeding, selection . . .
344-351
cross-fertilization or hybridiza-
tion
352-357
variation in
336-344
Soybean cake, duties on
454-455
exports of
532-533
imports of
453, 532-533
Soybean oil, contracts for sale of .491-493
competition from other oils. . .469-473
duties on
454-455
exports of
533
600
INDEX
imports of prices of supply of
453-454, 531-532 509-510, 519-524 455-458
utilization of in paint, soap, edible
products
463-467
Soybean oil meal, contracts for sale
of
491-193
duties on
454-455
exports of imports of prices of effect on use
532-533 453-454, 532-533 509-510, 524-528 526-528
use-values of in feeding utilization of
507-509 462-463
Soybean products, industrial, list of 460
feed, list of
460
food, list of
460
See also Soybean cake, Soybean oil , and Soybean oil meal
Soybeans, consumption of
459-475
costs and returns in producing. 448-453
disposition of domestic crop. . .459 160
duties on
454-455
exports of
530-534
gathered, distribution by uses. 473-475
genetics and breeding in improve-
ment of
See Soybean breeding
imports of..
453-454, 531-534
increase in importance of .427, 537-541
marketing of, costs in
493-503
information on
477-482
practices of price risks in
475-493 528-530
systems of, federal inspection. . 503-507
federal grade requirements. . 505-507
place of in Illinois farming. . .534-536
prices of, effect on use
526, 528
processing of, methods for. . . .467-469
production of in Illinois in selected countries
443-446 432-433
in the United States
433-443
seed, industrial uses for
486-491
price of sale of
510-519 482-486
supply of use of as feed for livestock
432-458 536
use-values of in feeding varieties of in Illinois
507-5 10 446-447
Sparta experiment field yields. . .273-274 Spinach, fertilizer experiments with
6-10,33-36
Springvalley experiment field yields ....274-275
Strawberries, tests with refrigerated
transportation
213-222
Sunlight, effect on flavor of milk and
cheese
580-581
Tallowiness, in milk and cream, biological factors related to. . .577-595 in dairy products, definition of. . 579-581
in honey-cream
553-555
Temperature conditions in refriger-
ated fruit cars, experiments on
159-224
See Contents
158
Toledo experiment field yields. .275-276 Tomatoes, fertilizer experiments with
21-25,33-36 Train schedules, influence on differ-
ences in intermarket hog prices 150 Trucks, use of in hog marketing. 558-576 Unionville experiment field yields. . 277-278
Urbana experiment field yields
278
Vegetables, causes of damage to dur-
ing shipment
81-119
West Salem experiment field yields. 278
UNIVERSITY OF ILLINOIS-URBANA
Q 630 7IL6B BULLETIN. URBANA 377-3891932-33
C002
30112 019529228

PH Tracy, HA Ruehe, RJ Ramsey

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