REAT advances have been made FREDUS N. PETERS, JR. This paper is a preliminary report during the past ten years in the The Quaker Oatscampany, Chicago, Ill., regarding edible a n t i o x i d a n t s with protection of perishable foodparticular emphasis on oat flour. A AND SIDNEY MUSHER stuffs from spoiling. More rapid transnumber of investigations on these prodDortation. better control of humiditv. Faundatian3 New N. y* ucts are in progress. W h i l e some hew and ’ improved refrigerants, and will be reported in the near future, better methods of handling and packaging have all served to the purpose here is to give a historical background for future papers as well as t o indicate some of the lines of study now make available fresher and more wholesome foods. However, while spoilage due to bacterial and mold growths has been being followed. greatly reduced, comparatively little has been done to deOver an extended period the Musher Foundation has been crease oxidative deterioration. As far as loss of flavor alone studying the value of cered flours as antioxidants in fats, oils, is concerned, deterioration due to oxidation is probably as and fat-containing foods. This work has already been partially described in certain United States and foreign patents. important as the biochemical changes just mentioned. In foods the most easily recognized sign of oxidative deBroadly, these patents describe a food product carrying a terioration is rancidity. Studies of rancidity and the role “coating of vegetative antioxidative substance” (16), an animal tissue carrying such a coating ( I S ) , a packaging maplayed by oxygen in its development (6, Q), as well as in the loss of vitamin (10, 20), have been made. Digestive disturbterial coated with antioxidative cereal or seed materials (14), ances have been traced to the ingestion of partially oxidized and the stabilization of fatty glycerides with cereal antiand rancid fats (21). However, rancidity is merely the final oxidants (16). From the standpoint of flavor and frequently result of a comparatively long series of reactions. Loss of of effectiveness, oat flour has advantages as an antioxidant aroma is the first stage. This is followed by development of over other vegetative materials such as corn flour, barlejflour, rice bran, etc. a bland or insipid flavor, and eventually the point of rancidity Special grades of oat flour are being marketed for different is reached. In this paper these progressive steps are grouped products under the brand name of “Avenex,” for application under the general classification of “rancidity” since they are to food materials by: (a) intimate mixing or infusion, as in all associated with oxidation. The logical means of preventing them is by either the use of antioxidants or prolard, oleomargarine, peanut butter, etc.; ( b ) dusting or coating, as on potato chips or salted nuts; or (e) coating paper or tection from oxygen, as exemplified by vacuum packaging. Many patents have been issued claiming that fats and oils other packaging material which comes into contact with foodcan be stabilized by substances such as carotinoid pigments stuffs such as butter, lard, bacon, coffee, etc. Products ( 1 7 ) , lecithin (4), hydroxy-polybasic aliphatic acids (19), treated with oat flour or Avenex are for convenience rehydroquinone (18), furfural (11), unsaturated polybasic ferred to in this paper as “Avenized.” aliphatic acids ( 7 ) , and gum guaiac (16). Intimate Mixing The use of many of these antioxidants is prevented by lack of approval of food administration officials and by the reTREATMENT OF FATS AND OILS.The effect of oat flour luctance of the public to buy focrds treated with such soupon the development of rancidity in lard is given in Table I. called chemicals. In the samples marked “unfiltered” the oat flour was added
G
“
I
146
INDUSTRIAL AND ENGINEEKIKG CHEMJSTKY
FEBRUARY, 1937
to the lard and allowed to remain in suspension during the test period. In the samples marked "filtered" the oat flour and lard were kept thoroughly mixed for 15 minutes at 150" F., following which the suspended material was removed by filtration. To determine the resistance to rancidity, air was bubbled through the lard a t 208" F., until a rancid odor was noted. In the following table the second column indicates the time required for a sample of lard to become rancid under these accelerated conditions. TABLE
r.
EFFECT
017
OAT FLOUR
Product Meached refined lard: Coni;rol Plus 1% oat flour unfilteied Plus 2 % oat flour unfiltered Plus 3% oat flour unfiltered Plus 4% oat flour unfiltered Plus 5% oat flour unfiltered Plus 10% oat flour unfiltered Plus 6p/, oat flour filtered Plus 10% oat flour filtered Prime steam lard: Plus 5% oat flour unfiltered Plus 10% oat flour unfiltered
ON
RANCIDITY OF LARD Elapsed Time, Hours 1.5 2.5 3.25 4 4.75 5.5 9 3 6.25
16 22
147
comparable to the improveinent obtained by the use of oat flour as an antioxidant when added directly to fats. When used in excess of 1 per cent, the oat flour develops a slight greenish cast in the oleomargarine and an objectionable mealy taste. A study is under way to determine the DAIRYPRODUCTS. value of oat flour in dairy products. It has been observed that, when 0.25 to 0.5 per cent oat flour by weight is added to liquid milk and it is subsequently spray dried, or when the oat flour is mixed mechanically with milk following the spraydrying operation, a substantial retention of fresh flavor and aroma and retardation of rancidity occur. SPECIALFOODPRODUCTS. Candies containing butter, milk, coconut oil, or other fatty ingredients, and mayonnaise, salad dressing, powdered egg yolk, peanut butter, p.repared pie crust mixes, doughnut flours, and ice cream mixes are products in which loss of flavor and development of rancidity frequently occur. Complete analytical data are not available to indicate the exact value of adding oat flour to such products, although experiments have been made with all of these and the indications are generally favorable to the use of oat flour as an antioxidant.
Dusting or Coating of Food Products
Preliminary tests with rice bran and rice polish indicate that these may be even more effective than oat flour as far as rancidity protection of lard is concerned, but they impart more color and flavor than the latter. Table I1 indicates the comparative activity of white and yellow corn flour and oat flour in cottonseed oil compound shortening. A similar study was made on refined castor oil.
The second method of applying oat flour is as a continuous or discontinuous surface coating over food products subject to the development of rancidity. POTATO CHIPS . ~ N D SALTEDKuT6. The processing 6f potato chips in hot oil followed by exposure of the flake to air makes this product particularly susceptible to rancidity. Oat flour may be dusted over potato chips to the extent of TABLE11. COMPARaTIVE ACTIVITY O F CORN AND OAT FLOURS 1 to 3 per cent of the total weight of the chips, or it may be mixed with salt and both ingredients can then be added a t IX COTTONSEED OIL SHORTENING AND REFINED CASTOR OIL once. To be effective, the dusting should be done while the Product Elapsed Time, Hours chips are very hot. This allows the antioxidant to be ab6 sorbed by the oil, thereby spreading it over the entire surface 14.5 12.5 of the chip. A comparison is made in the following table 13 of the peroxide numbers of fat extracted from untreated chips Refined castor oil: 3 Control and chips treated with oat flour: 32 Plus 67' oat flour unfiltered Plus 5 oat flour filtered Plus 6$ white corn flour unfiltered Plus 6 white corn flour filtered
12 15
Since the objectionable characteristic flavor of refined castor oil is a result of oxidative rancidity, the addition of edible antioxidants to castor oil is of definite value from the standpoint of palatability. An outside research laboratory studied the effect on peroxide values of refined corn and soybean oils when treated with various cereal flours. In these tests 100 cc. of the oil were exposed in an open flask a t room temperature and in diffused daylight. Peroxide values, expressed in milliequivalents, were determined at the end of the indicated periods (Table 111). The filtered samples were prepared by infusing tke flour in the oil for 15 minutes at 150"F. (66' C.) followed by filtration. Much of the unpalatability of fish oils is a direct result of oxidative changes which not only affect the flavor but cause .I serious loss of vitamins A and D. The value of oat flour ns an antioxidant in fish liver and fish oils is being studied under a fellowship of the Musher Foundation established at the Seattle Technological Laboratory of the United States I3ureau of Fisheries. From 0.5 to 1 per cent of oat flour may be used in oleoiiiargarine to retard rancidity or undesirable oxidative changes. The oat flour may be added to the fat, and the mixture of rat and oat flour used in the manufacturing operations in the regular way; or the oat flour may be added with the salt. The improvement in the oleomargarine containing oat flour is
Peroxide No. after 30
Potato Chips Untreated Aveniaed
8
Dayb
30.42 7.36
Similar results are obtained with roasted and salted nuts. A batch of jumbo peanuts was divided into two portions. One was treated with 1.5 per cent oat flour while still hot. Twenty-four hours later there was a marked difference in the odor of the two products: the treated sample had the original fresh aroma, whereas the untreated was already becoming TABLE111. PEROXIDE ,--Refined Time, Weeks 0 1
Control
VaLTJEs
Coni Oil--Refined Soybean Oil-Plus 7.5y0 Plus 7.5% Plus 7.5% oat flour Plus 7.5% oat flour oat flour unoat flour unfiltered filtered Conti 01 filtered filtered
2 3
4 5 6
Refined Corn Oil Plus 7.5%
Time, W'eekn 1 4 5 6
rye
flour
Control filtered 7.1 7.0 48.0 33.5 51.0 70.0
36.5 53.0
Plus 7.5% rye flour
unfiltered 6 0 34.0 34.5 35 0
Plus 7.5%
whole wheat flour
filtered 9 2 43.7 47.5 56 0
PIUS - .--
Plus
7.5%
whole wheat flour unfiltered 4.0 31.7 30.5 44.0
Plus 7.5'%
7.5%
32:5
a:O
oat oat flour flour unfiltered filtered 1.2 0 9 .. ...
VOL. 29, NO. 2
INDUSTKMI. 4NL) ENGINEERING CHEMISTRY
148
bland. Peroxide numbers of the oil expressed from the% s&mples were determind. Some of these nuts were made into candv bars. and similar Deroxide determinations were made. The results of these tests are as follows:
TABLE IV,
CoMk'~RrsoN OF EFFECT 08' BRINE SOLUTIONR ON SPANISH MACKEELEL
~~
samoie ~ e e n u t suntreated ~ ~ pius oat ~ nour~ ~ CBndy with untreated nuts Csndy with treated nub
No. alter:-38 davi 64 deya
--Peioxide 13 . davs
5.26 1.96 t 4.22 2.13
a
5.16
4.81 1.95 3.83
7,
..
7
9
1:46 4.80
The application of this process to potato chips and salted nuts wm the fist commercial sonlieation of Avenex and the fact that most of the original purchasers are continuing the use of the product is convincing evidence of tho effectiveness of oat flour as an antioxidant for the production of such products. FATTYFISH AND FISHERY PROD~JCTS. The "fishiness" of fatty fish, such as mackerel, sarclies, salmon, herring, tuna, etc., is almost entirely due to the oxidation of the fish oils. Upon exposure the oil in the outer surfaces of fatty fish bo comes separated from the tissues, causing rapid oxidation and rancidity. The characteristic indigestible reaction that frequently comes from eating salt mackerel, smoked fish, or canned fish may be due to oxidative deterioration, which also causes the loss of vitamin A in fish oils. Hart (6') observed that oat flour has value as a means for retarding deoom p o s i t io n of fattymackerel held under room temperature conditions. A number of e x p e r i m e n t s with Spanish mackerel were made to compare the action of ordinary hrinc with brine plus oat flour (Table IV). feet of variation of
..
Time, Days
1. 1 .
% '
*Iter days' Pqroxide No. I I aays
A.
I600 g. water. 200 s. B . 1800 g. water, 200 g. Belt, 200 8. oat Ao"r ss1t 5 observers sgresd that A was aupeiior 6 of 7 obaarvers deelsred A 8uperior in odor and appearsnoe 5 of 6 observers pronounced A superior in odor and BppeaisnOB
A l l ohservera daolsied A far ~uoerioi ~~. ~
~
~~~
0.025
.^
4."
~~~
~
."
0.073
I"."
concentration is given in Table V. Table VI presents data on treatments with several types of mixtures. The fish used for these tests came from different lots, and hence the data
FEBRUARY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY OF VARIATION IN OAT FLOUR CONCBNTRATION TABLE v. EFFECT
1800 g. water, 200 g. salt, 50 g. oat flour Best Best Best Good shape Best 0.000030 0.039
Time, Days 2 5 8 10
13 HaS on 13th day % NH, on 13th da;, % '
ON
Submerged in S o h . of: 1800 g. water, 200 g. salt, 100 g. 1800 g. oat flour Beat Best Best Good shape Best 0.000030 0.041
149
SPANISH MACKEREL
water, 200 g. salt, 200 8. oat flour Inferior Sour oat odor Sour oat odor Bad oat odor Sour odor 0.000030 0.041
-
1800 g. water, 200 g. salt Inferior Definitely fishy Strong fishy odor Strong flshy odor Putrid 0.000070 0.063
TABLEVI. EFFECTOF VARIOUS MIXTURES ON SPANISH MACKEREL Time, Days 2 4
6 10
A.
-Submerged in S o h . of: 1600 g. water, 200 g. oat flour, B. 1800 g. water, 200 g. salt C . 1800 g. water, 200 g. oat flour 200 g. salt A and B about same Slightly superior t o IV ... Stale Slightly k&erior t o B ... Stale Putrid ...
D.
2000 g. water
Fair condition Putrid
...
.. .
TABLEVII. EFFECT OF DUSTING EVISCERATED SPANISH MACKEREL WITH OAT FLOUR Time, Days
0
TreatedQ
-Per
Odor
7
B . Untreated 1 Best Inferior; when first out open a strong odor which disappeared on standing 2 Superior Fishy 3 Slightly fishy but muoh superior t o B Putrid Sprinkled with 0.8% by weight whole pulverized oats. A.
for one table cannot be compared with those for another. The results obtained by dusting Spanish mackerel with pulverized whole oats are shown in Table VII. I n the determination of hydrogen sulfide present, a modification of the Eber test was used (1). The ammonia present was determined by the standard A. 0. A. C. method for fish and fishery products. Anderson (8) observed that the addition of 1 to 2 per cent of pulverized whole oats to salmon waste previous to the drying operation resulted in meals whose fat content showed markedly lower peroxide numbers. Anderson's studies are being continued to determine the relation between the chemical changes and biological values of the treated us. untreated meals. Other studies have been undertaken by the Musher Foundation to determine the value of ground oats and oat flour in retarding oxidation and development of rancidity in fish liver and body oils, and in frozen, canned, cured, and fresh fatty fish. These studies are being made principally with salmon, herring, and sardines that present the most serious problems to the industry. COFFEE. The highly oxidizable coffee bean oil is recognized as being responsible for the rapid deterioration in quality of ground roasted coffee. The addition of 3 per cent of oat flour retards this development of staleness and rancidity. The flour was dusted over the surface of the coffee beans as they left the roaster and were still hot. Under these conditions the oil, which exists in a thin film over the surface of the coffee bean, is exposed to oat flour in a manner similar to that described in the discussion of roasted nuts and potato chips. The coffee beans were then ground in the regular manner. Tests were conducted in an effort to determine the comparative improvement in roasted coffee to which oat flour was added. Following the method proposed by Bengis (S), in which the so-called oxidizability value was used to determine the degree of staleness, tests were conducted with Avenized and untreated coffee. The results indicated that the Bengis method may be used in correlating changes in the flavor of coffee treated with oat flour. Fairly good correlation between coffee flavor and the Reichert-Wollny number has been obtained in some cases.
Cent H2S-Per Cent "3--Peroxide UnUntreated Treated@treated Treateda
Treateda
0.000005 0.000010 0.019 0.000005 0.000010 0.032 0.000005 0.000020 0.036
0.021 0.032 0.034
0.0 0.0
2.4
No.Untreated 2.2 3.4 8.2
The following table gives results obtained by Reichert; Wollny determinations on treated and untreated coffeethe treated coffees contained 3 per cent by weight of oat flour: Coffee Untreated Treated Untreated Treated
Method of Packing I n carton I n carton Under vacuum Under vaouum
-Days 0 0.463
0.370 0.442 0.487
after Openin-. 8 0.473 0.477 0.279 0.466 0.462 0.578 0.509 0.545
4
12 0.623 0.538 0.647
0.1308
Organoleptic observations were made by Florence (6) on different grades of coffee treated with different amounts of oat flour. Particular attention was given to Santos coffee to which 3 to 4 per cent of oat flour was added to the hot coffee beans immediately following roasting. An artificial system of scoring was established, based upon 100 for freshly roasted coffee with its full flavor as against 0 for coffee totally lacking in flavor. The scoring of Santos coffee treated with varying amounts of oat flour is given in the following table; all coffee was stored in the ground form: Untreated coffee Coffee 6% oat flour
+
Untreated coffee Coffee 4% oat flour
+
-Score 1 day 95 98a
a t End of:-3 days 5 days 90 75 986 900 4 days 87 97d
15 days 50 85d
1 day 3 days 4 days Untreated coffee 87 80 75 Coffee 37, oat flour lOOd 98" 85d Predominant oat flavor; no change in appearance of brew. Very slight oat flavor. No oat flavor. No oat flavor; no change in appearanoe of brew.
+
a
b C
d
SPECIALFOOD PRODUCTS. Whole-wheat biscuits treated with oat flour are improved both in flavor and keeping quality. Preliminary reports indicate that oat flour dusted over the surface of frozen cream delays the development of tallowy flavors.
Packaging Materials From the commercial point of view the addition of oat flour to coffee, lard, and similar products has one great disadvantage because its presence must be declared on the
MACHINEFOR MAKINGGREASE-PROOF PAPER
label. However, if such products are wrapped in paper carrying a surface coating of oat flour, some protection is given to the product and no special labeling is required. A number of paper manufacturers are now making Avenized papers which carry a coating of oat flour amounting to from 1 to 5 per cent by weight of the total packaging material. Oat flour is applied to unwaxed papers by surface sizing and to waxed papers by incorporating 35 parts of flour with 65 parts of wax by weight. In products such as lard or butter all surfaces are in direct contact with the packaging material; consequently, the use of oat flour as a sizing will result in complete coverage of the product by the flour. I n order to determine the effectiveness of Avenized parchment for the wrapping of lard as a means of retarding rancidity, the following observations were made at an outside laboratory and are published with permission : One-pound packages of bleached lard were wrapped with regular 40-pound parchment, Avenized 30-pound parchment, and Avenized $£ parchment. The packages were held a t room temperature in diffused daylight. At intervals the three different types were opened, and a physical inspection was conducted for odor and flavor. Samples were then taken (a) from the sides and top where the lard had been exposed to the parchment, (b) from the center, and (c) from the remainder of the sample after (a) and (b) had been removed. These were tested for peroxides, and result? are given in milliequivalents per gram in Table VIII.
Weeks from Start of Test 0
--Side
Kegular ParchmentCenter Balance
-
Whole"
Courtrslj, Rhanelonder P a p e r C o m p a n y
Judging from the peroxide values alone, these data indicate an improvement, particularly after %week storage on the samples wrapped in treated paper. The peroxide numbers of lard thinly coated on sheets of Avenized and untreated glassine were determined. The results were as follows: Days of Storage --.
--
Glassine Untreated Avenized
0
1
2
3
6
8
1.25 1.25
3.56 2.44
6.00 4.78
8.90
12.50 6.60
19.70 12.60
4.90
Products such as butter, lard, or bacon keep better when wrapped in an Avenized than in an untreated paper because the surface of the product is in intimate contact with an oat flour surface. It is somewhat surprising, however, to note the protection sometimes conferred on other products. For example, potato chips packed in Avenized paper bags will generally remain free from rancidity for a longer time than when packed in ordinary bags. Differences have been observed in the odor of the fat adsorbed on the surface of the bag aiid also in the keeping quality of the chips themselves. Probably the catalytic activity of the rancid oils adsorbed on the surface of the paper is responsible for the rapid deterioration of potato chips packed in the ordinary paper bags. The use of Avenized papers for the packaging of caramels and candies, flour mixes, chocolate, ice cream, powdered whole milk, and other fatty foods, normally subject to surface oxidation, is being studied.
TABLEVI11 30-Lb. Parchment Treated with Oat Flour
Side
Center
2.2 4.6 4.3 4.1 4.5 7.8 9.3 10.8
Balance
Whole"
2.2 2.2 2.2 3.0 3.0 3.0 1 4.41' 3.6 3.6 4.8 4.3lJ 3.4 2 4.0 1.9 2.1 4.1 3.4 3.4 1.8 2.0 4.0 3.4 3.4 3 4.0 4 4.2 2.1 2.3 4.2 3.6 3.5 5 7.5 6.0 7.1 8.3 8.4 8.0 6 5.4 3.7 7.3c 6.8 5.9 5.3 8 7.4 12.3 12.0 6.4 6.5 7.7 * Calculated by assuming 5 per cent was used for the side sample, 5 per cent for the center, and 90
f o r these samptes were then averaged proportionately.
Center sample included top surface. Average of side and center only (balance sample is out of line).
150
3.0
3.5 J .5
40-Lb. Parchment Treated with Oat Flour Side Center Balance Wholea 4.0 4.5 3.6 3.5 3.7 6.9 6.7 6.7
4.0
...
3.4 3.4 3.7 7.0 5.9 7.6
3.5 3.6 8.0 5.4 7.5 per cent for the balance sample.
4.0 2.5 3.1
3.0 3.2 6.0 5.6 9.1
4.0 2.7 3.2 3.1 3.3 6.0 5.6 8.9
The peroxide values
FEBRUARY, 1937
INDUSTRIAL AND ENGINEEHING CHEMISTliY
It has been found that the use of Avenized cartons for whole-wheat shredded biscuits which are usually packaged without an inside paper liner is of value not only in delaying the development of rancidity but also in retarding the transfer of board odors and flavors to the food. Reichert-Wollny numbers on vacuum-packed coffee with and without Avenized liners were as follows: Vacuum Can Unlined W i t h Avenized liner
0
Days after Opening ---. 3 6 9
0.392 0.359
0.407
0.327
0,531 0,465
0 570 0.348
Enough data on the use of oat flour as an antioxidant have been given to indicate that here is a new field for investigation. More exhaustive studies may show that only with certain foods is the addition of oat flour sufficiently protective to warrant the additional expense involved. Oat flour does, however, offer possibilities of improving the quality of many products now being sold.
Literature Cited (1) Allen, “Commercial Organic Analysis,” 5th rev. ed., Vol. I X , p. 323, Philadelphia, P. Rlakiston’s Son & Co., 1932.
151
(2) Anderson, Lyle, unpublished progress report from Musher Foundation, Inc., a t U. S. Bur. Fisheries, Seattle, Wash ( 3 ) Bengis, R. O., IND.ENG.CHEM.,28, 280 (1936). (4) Bollmann, H . , U. S. P a t e n t 1,575,529 (March 2 , 1926). (5) Florence, E. B., N. Y . Coffee & Sngar Exchange, unpublished data. (6) French, R. B., Olcott, H . S.,a n d Mattill, H . A , , ISD. ENG. C H E Y . ,27, 724 (1935). (7) Greenbank, G . R . , U. S. P a t e n t 1,898,363 (Feb. 21, 1933). (8) H a r t , W. J., unpublished progress report from Musher Foundation, Inc., a t U. S. Bur. Fisheries, College P a r k , Md. (9) Holm, G. E., Greenbank, G. R , a n d Deysher, E. F.. IND.ENG. C H E M . 19, , 156 (1927). (10) Hopkins, F. G., Biochem. J.,14, 724 (1920). (11) H u b e r t , J . P., U. S. P a t e n t 1,680,047 (Aug. 7 , 1928). (12) Musher, Sidney, Zbid., 2,026,697 ( J a n . 7, 1936). (13) Ibid., 2,029,248 (Jan. 28, 1936). (14) Ibid., 2,038,752 (April 28, 1936). (15) I b i d . , 2,049,017 (July 28, 1936). (16) Newton, R. C., a n d Grettie, D . P., Ibid., 1,903,126 (March 28, 1933). (17) Newton, R . C., a n d Richardson, W.D., Ibid., 1,890,589 (Dee. 13, 1932). (18) Nitardy, F. R., Ibid., 1,879,762 (Sept. 27, 1932). (19) Rogers, T. H . , Ibid., 1,805,458 ( M a y 12, 1931). (20) Steenbock, H . , Boutwell, P . W., a n d K e n t , H. E., J. Hiol. Chem., 35, 517 (1918). (21) Whipple, D. V., J. Pediatrics, 8, 734 (1936).
RECEIVED September 14, 1936
Cereal Flours as Antioxidants for Fishery Products Halibut Liver and Salmon Oils LESLIE LOWEN, LYLE ANDERSON, AND ROGER W. U. S. Bureau of Fisheries, Seattle, Wash.
Various substances have been reported to be effective antioxidants. I n this investigation attention was given to the cereal flours because they are food materials of bland odor and flavor, readily available at low cost and, if effective, acceptable without question by food regulatory bodies. The antioxidant value of oat flour was tested on experimentally prepared halibut liver oils and commercia1 salmon oil. Oat flour was found to retard the initial peroxide formation, and its effectiveness in retarding rancidity increased as less accelerated conditions of exposure to air were used. The salmon oils showed a more pronounced retardation of oxidation and of off-odors and flavors than was noticeable in the halibut liver oils. There were sufficient favorable results in each case to warrant further investigation.
T
HE development of rancidity in fats and fat-bearing materials is associated with certain oxidative changes in the fat. The rate and exHARRISON tent of such reactions can be influenced by the presence or absence of oxygen, exposure to light, prevailing temperatures, and the incorporation or presence of certain prooxidant or antioxidant substances. The characteristic odors and flavors developed are attributed to the formation of various aldehydes, ketones, and acids. Food industries are concerned with rancidity because the development of oft-odors and flayors, together with chemical changes associated with them, decreases the quality, market life, and sales value of the product affected. As early as 1890 Langbein and Stohlman (18) reported that rancid lard was of lower calorific value than fresh lard. More recently Whipple (39, 40) obtained evidence of the formation of toxic compounds and loss in nutritional value in rancid oils, and Powick (%), Mattill (do), and Whipple (58) reported that rancidity tends to destroy vitamin A. The fishing industry is particularly confronted by the problem of rancidity because fish oils are, in general, highly unsaturated and are therefore extremely susceptible to oxidative deterioration. This pertains to both the extracted oils and to fresh and preserved fishery products. Such preservative methods as chilling, freezing, smoking, salting, and canning were developed primarily for retarding proteolytic decomposition and do not in all cases protide suitable protection against oxidative deterioration. On this account and because of further limitations in controlling oxidation during normal storage and distribution, there is need for
