OCTOBER,
1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Literature Cited (1) Arup, Paul, AnaEyst, 53, 641-4 (1928). (2) Assoc. Official Agr. Chem., Official and Tentative Methods, 4th ed., p. 414,Washington, D. C., 1935. (3) Atkinson, H.,Analyst, 53, 520-30, esp. 525 (1928). (4) Barthel, Chr., and SondBn, Klas, 2. Untersuch. Nahr. u. Genussm., 27,439-53 (1914). (5) Cranfield, H.T.,Analyst, 40, 439-42 (1915). (6) Crowther, Charles, and Hynd, Alexander, Biochem. J., 11, 139-63 (1917). (7) Currie, J. N., J. Agr. Research, 2, 1-14 (1914); 2, 429-34, esp. 431 (1914). (8) Dhingra, Das Ram, Biochem. J . , 27, 851-9, esp. 855 (1933). (9) Doane, C. F., and Matheson, K. J., U. S. Dept. Agr., Bull. 608 (1934). (10) Dons, R. K.,2.Untersuch. Nahr. u. Genussm., 15,72-4 (1908). (11) Fahrion, W., Z . angew. Chem., 31, 1219-28 (1907). (12) Faltin, A., and Dedinszky, G., KisSrletZlgyi Ktizlem6nyek, 33, 62-76 (1930). (13) Funder, Ludwig, Molkerei-Ztg. (Hildesheim), 49, 78-9 (1935). (14) Jamieson, G. S.,J. Assoc. Oficial Agr. Chem., 13, 255-8 (1930). (15) Johnson, R. C. H., Analyst, 58,469 (1933).
1171
(16) Lewkowitsoh, J., “Chemical Technology and Analysis of Oils, Fats and Waxes,” 6th ed., New York & London, MacMillan Co., 1923. (17) Marre, E., “Le Roquefort,” Rodez, E. CarrBre, 1906. (18) Marres, Paul, “Les grandes causes,” Tours, Arrault et Cie, 1935. (19) Martin, Ann. fals., 6,662 (1913). (20) Palmer, L. S.,J . Biol. Chem., 27, 27-32 (1916). (21) Palmer, L. S.,and Eckles, C. H., Ibid., 17, 191 (1914). (22) Ibid., 18,261 (1915). (23) Polenske, Ed., 2. Untersuch. Nahr. u. Genussm., 7,273 (1904). (24) Reubenbauer, Henryk, Przemysl Chem., 14, 169-78 (1930). (25) Rogers, L. A,, Associates of, “Fundamentals of Dairy Science,” A. C. S. Monograph 41, 2nd ed., p. 87, New York, Reinhold Pub. Corp., 1935. (26) Schlag, Hanna, Molkerei-Ztg. (Hildescheim), 49, 176-7 (1935). (27) Siegfeld, Z . Untersuch. Nahr. u. Genussm., 13,516 (1907). (28) U. S. Dept. Agr., Food and Drug Administration, Service and Regulatory Announcements, Definitions and Standards for Food Products for Use in Enforcing the Food and Drugs Act, No. 2, Rev. 5, Nov., 1936. RECEIVFID June 10, 1937.
Fish as a Source of Vitamins
A and D Herring, Brisling, and Their Products GULBRAND LUNDE, VALBORG ASCHEHOUG, AND HANS KRINGSTAD Research Laboratory of the Norwegian Canning Industry, Stavanger, Norway
Fresh, smoked, and canned brisling and herring, caught in different localities, in different years, and a t different periods of the year, were tested for their vitamin and D potency. Brisling oil contains 8 t o 64 I. U. of vitamin A per gram and 70 to 140 I. U. of vitamin D. No loss of vitamin A and D occurs as a result of the smoking and canning process or of the storage of the canned product. Canned brisling contain 90 to 960 I. U. of vitamin A and 1000 to 3000 I. U. of vitamin D per 100 grams. The vitamin A content of the body oil of herring is 2 t o 38 I. U. and of the liver oil, 3600 to 11,000 I. U. per gram. The vitamin D content of body oil of fresh winter herring is 90 to 150 I. U. per gram. The vitamin A content is not affected by the smoking process but is considerably decreased by the canning process; the
vitamin A content of canned kippered herring ranged from a trace t o 50-60 I. U. per 100 grams. The vitamin D content, however, is unchanged by smoking and canning; canned kippered herring contain 840 t o 2000 I. U. per 100 grams.
A
REVIEW of the literature shows that very few and incomplete investigations have been made of vitamins A and D in canned fish products. T o determine the
vitamin potency of American canned salmon, Tolle and Nelson (23) subjected samples of oil from canned offal of five species of salmon to biological assay. The vitamin A potency of herring and brisling oil was determined by Lunde, Kringstad, and Vestly (9),the vitamin A content of herring by Notevarp (16). The Schmidt-Nielsens (20) tested the vitamin potency of herring body oil and of canned kippered herring and brisling. Scheunert and Schieblich (18) determined the vitamin A content of herring. Lunde (8) tested the vitamin D content of raw and canned brisling in this laboratory. Ahmad and Drummond ( 1 ) determined the vitamin A potency of the body and liver oils of herring. Of the species of fish related to the brisling and herring the Swedish Xtroming (Clupea harengus) was examined for its vitamin content ( 3 ) . Several investigators (9, 4, I S , 16, 21, 22, 24) tested the vitamin A and D potency of the California sardine and of menhaden oil. The Japanese sardine was tested by Matzko (14).
INDUSTRIAL AND ENGINEERING CHEMISTRY
1172
VOL. 29, NO. 10
These citations represent scattered investigations from which no conclusions regarding the vitamin potency of fish oils can be drawn. The vitamin A and D potency of oils from the same species of fish seemed to show considerable variation. To obtain a true picture of the vitamin content of marine oils, therefore, it was decided that a great number of samples must be examined.
The contents of four to six tins of brisling in olive oil were used. The oil was poured off and the fish was mixed in a mortar with anhydrous sodium sulfate as described above; afterwards it was extracted with ether in a Soxhlef apparatus. The extracted oil was then mixed with the olive oil poured from the tin. I n this way was obtained the total fat content of the canned product.
Preparation of Fresh Samples
Determination of Vitamin A
Samples of herring (Clupea harengus) and of brisling (Clupea sprattus) were taken from the most important fishing grounds several times during the season. The samples brought from a distance were packed in ice, and the preparation of the oil samples was carried out as quickly as possible after their arrival in the laboratory, in the two following ways:
Three methods are in use for the determination of vitamin A : (a) the spectrographic method which measures the extinction coefficient a t 328 mp, (b) the color reaction with antimony trichloride (Carr-Price method), and (c) the biological method. The spectrographic method is found to give accurate results only for concentrates and for oils of high vitamin A potency, in spite of attempts of several investigators to adapt the procedure to oils with a low vitamin A potency where the absorption of other substances in the oil is large in comparison with the vitamin content (6, 6, 7, 12, 21). Consequently, vitamin A in herring body oils have to be determined either by the biological method or the Carr-Price reaction. The Carr-Price reaction was carried out on the unsaponifiable matter; the blue color was measured in the Lovibond tintometer in a dilution that gave readings of about 5 blue. Serious objections have been raised by many workers as to the reliability of this reaction. Substances other than the vitamin -for instance many carotinoids-give this color reaction with antimony trichloride, I n the present investigation, however, there is no reason to believe that enough of these substances are present to have any effect on the reaction. When the reaction is carried out on the oil itself, substances may be present that will inhibit it and give too low values. All the determinations were therefore made with the unsaponifiable matter. The determinations on the herring liver oils of high vitamin A content were made spectrographically (absorption a t 328 mk) as well as colorimetrically in the unsaponifiable matter, and give satisfactory agreement. The unsaponifiable matter was prepared according to the method recommended by the International Committee on Vitamin Standardization, taking 5 to 10 grams of the oil for saponification. The work was done in an atmosphere of nitrogen or carbon dioxide. The vitamin content was calculated in International Units according to the method of the committee.
1. HIATINGAND PRESSINQ. Two to three kilograms of fish were ground in a meat chopper; the mass was heated with brine in an atmosphere of carbon dioxide to 80" C l in a water bath and ressed through a cloth. The oil was separated from the water gy centrifuging, filtered, transferred to amber colored flasks, and stored at a low temperature. 2. EXTRACTIONS WITH ETHER. One hundred to two hundred grams of the ground mass were mixed with anhydrous sodium sulfate in a mortar until a dry owder was obtained. This powder was transferred to a flask w i d a ground-glass stopper, the flask was filled with carbon dioxide, and 200 to 300 cc. of peroxidefree ether were added and shaken for 20 minutes in the shaking machine. The ether solution was filtered through a cloth and dried for 3 t o 4 hours with anhydrous sodium sulfate, and then filtered into a distilling flask; the main portion of ether was distilled off and the rest was evaporated in vacuum.
Both methods yielded oils of the same vitamin potency. Method 2 was quicker and was preferred for the small samples of oils in the vitamin A determinations.
Preparation of Canned Fish The contents of four to six tins of the kippered herring were used. The same method as described above was employed; that is, the material was subjected to cooking, and then the oil was expressed or extracted.
TABLEI. Sample No.
SUMMARY O F
Fishing District
Date of Catch
DATAON BRISLING EXAMINED Av. Length of Fish
Av. Weight of Fish
Cm.
Gama
Fat Content. of Fish Fresh Smoked
%
% 15.5 14.6 20.5 15.5 l4:7
1933 1 2 3 4
Ryf yl ke Ryfylke H ardanger Ryfylke
8/6 15/6 l6/6 14/6
l0:l
.. ..
7:0
.. ..
11.4 9.8 16.5 11.4
5
6
7 8
Sogn Sogn Hardanger Ryfylke
23/6 5/7 11/7 13/7
10:3 9.6 10.2
7:9 6.4 7.7
8:Q 8.6 9.0
9 10 11 12
Romsdalen Romsdalen Romsdalen Romsdalen
20/7
11.1 10.6 10.6
9.8 9.1
..
8.6
..
12.2 14.2 12.5 13.0
13 14 16 16
Sogn Hordaland Sogn Sogn
25/7 31/7
10.2 10.7
6.6 8.4 7.7 6.5
7.2 6.6 8.1 7.3
17 18 19 20
Hordaland Oslof j ord Hordaland Sogn
12/9 21/9 26/9 27/9
10.5 11.3 12.3 11.1
7.8 11.6 13.5
10.0 14.6 15.2 12.4
21 22 23 24
Ryfylke Ryfylke Ryfylke Ryfylke
20/5
1936 9.1
25 26 27
Sogn Sogn Sogn
8/7 14/7 18/7
18/7
21/7 22/7
$;:
3: 16/6
l::;
9":;..
9:3 10.0
10.0
..
.. .. ..
.. ..
..
.. .. .. ..
lk:4 (9.8)
.. ..
13.5
.. .. *. ..
8.8 9.9 9.7 8.4
12:s
5.:4 14.6
8: 4 20.8
..
Determination of Vitamin D by Biological Assay The same samples of oils were used in the vitamin A determination and for the biological test of vitamin D. * The numbers originally assigned to the oils were kept for the biological assay. A modified Poulsson and Lovenskjold procedure ( 1 7) was used for determining the vitamin D potency of the oils. The princi le involved is the measurement of the initial degree of rickets anxof the subsequent healing through calcification b the use of radiographs. However, the test period was extendelfrom 6 to 10 days. Rats weighing approximately 60 grams and about a month old were fed the diet 84 of Sherman and Pappenheimer, consisting of patent flour, 85 er cent; egg albumin, 10; calcium lactate, 2.8; sodium chlori&, 2; and ferric citrate 0.2. In addition, each rat was fed 2 to 3 grams of spinach per day as a source of vitamin A. At the end of 3 weeks the hind legs of each rat were x-rayed. Occasionally one or more rats in a litter proved less rachitic than the others and they were discarded, so that the same degree of rickets was obtained in all the experimental animals. The oil t o be examined was diluted with refined peanut oil and given in doses of 3 t o 5 standard drops (70 to 117 mg.) per day per rat. The international vitamin D standard prepared at the National Institute for Medical Research, London, was diluted
OCTOBER,1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLE11. VITAMIN A CONTENT OF FRESH, SMOKED, AND CANNED BRISLINQ
1933
I
12
11
2 3 4 5
11 11 11 27
11
6 7 8 9 10
29 10 44 15 32
29
50
11 12 125 13 -_ 14 15
30 26
26
43 64 32
.. 64 ..
1"
16 17 18 19 20 21 22 23 24 25 26 27
..
..
46
za SY
49 36 1936 8 26 12 32 32 57 26
5 5 3 3 5 11
..
11 10
..
.. ..
.. .. ..
14
.. ..
..
..
..
.. ..
490
..
..
..
... ...
... ...
320 300
18
59
530
..
... ... ... ... ...
.
.. .. .. *. ..
. I
..
35
.. .. ..
23 21
I
^ ^
150 150 90 90 160 330
13 11
..
u
11 11 8 6 10
..
.. .. .. .. ..
...
...
vitamin potency of the fish oils seems to increase as the fishing season progresses, and the concentration of vitamin A seems to be highest in fish with the lowest fat content. Later in the summer the latter relation seems to be less evident, as the later figures for vitamin A of the samples are rather high and seem to be independent of the fat content of the fish. Schmidt-Nielsen and collaborators also found a certain regularity in the variation of the vitamin content and the fat content of the liver of teleosts (19). T Examination of the vitamin content of oil from ten samples of smoked brisling showed the same amount of vitamins in the smoked fish as in the raw. The vitamin A content of ten samples of brisling canned in olive oil and also of the total oil (fish oil and olive oil) was determined. The relation between the fish oil and the olive oil in canned brisling was reported by Lunde and Mathiesen (11). Table I1 shows that vitamin A was not influenced by the canning process. I n order to determine the effect a t storage, seventeen samples of brisling stored for 2 to 4 years were tested. The following results show evidence of no destruction of vitamin A during storage: Vitamin A Content I U
..
.. .. 32 .. ..
1173
Q
Packed in an aluminum can.
..
in the same manner with peanut oil, and doses of this standard were given to the rest of the rats. After 6 days all of the rats were x-rayed, and the experiment was continued. At the end of the 10 days a new radiograph was taken of each rat, and the degree of healing was estimated by comparing the radiographs of each animal given the oil to be examined with those given graded doses of the international standard. The rats were weighed regularly during the test period. Preliminary tests were made t o determine the approximate vitamin D potency of the oils. The test was then repeated with different doses of the sample and of the standard. A large number of animals was used t o obtain concordant results.
Examination of Brisling The samples of brisling were taken from twenty different catches in 1933 and seven catches in 1936. The catches were made in different localities and a t different dates during the fishing season. The length, weight, and fat content of the fish were examined for most of the samples. The fat content of the smoked fish was also determined whenever this and the corresponding canned product were used for the vitamin determination. Table I gives a summary of the data. The fat content of the smoked fish is somewhat higher than that of the raw fish because of evaporation during the smoking process.
Vitamin A in Brisling The vitamin A content of brisling oil from the raw and smoked product is given in Table 11. I n the twenty-seven samples of raw brisling a varying vitamin A potency (from 8 to 64 I. U. per gram of fat) was found. Comparison of Table I1 with Table I shows that the lowest figures for vitamin A are obtained early in the season and seem to increase later in the summer. Also the vitamin A potency seems to be inversely proportional to the fat content of the samples of fish caught a t the same time. However, these experiments are not numerous enough to justify any conclusions, but two factors are important: The
Sample No.
Age Months
Per gram of oil
Per'lob grams
of canned
product
Sample No.
Age Months
Vitamin A Content I U Per' lob Per granu gram of canned of oil product
Packed in aluminum.
Vitamin D in Brisling Eleven samples of raw brisling (1933 and 1936 catches) were tested for vitamin D content with the following results: 1933
Sample No. Daily dose
N o . Vitamin of D in
rata
Mo. 3 4 8 12
15, 20, 25
11 11 15
12 10 8 4
-.,---
oil
I. u./ gram 70 140 130 90
Sample No.
1936
Daily dose
No. Vitamin of rats
MQ. 21 22 23 24 26 26 27
11 14,22 15 13, 17,21 15 11, 16 14
4 8 4 10 4 8 8
Din oil
I. u./ gram 120 80 90 100 100 126 90
In contrast to the vitamin A content, there is very little variation in vitamin D which averages 100 to 120 I. U. per gram of fat. The vitamin content of four samples of smoked brisling showed figures of 60 to 120 I. U. per gram, indicating that the smoking process had no injurious effect on vitamin D: 1933
Sample No.
3 4 12
No. Vitamin of D.in
Daily dose rats Mu. 17,24 10,20 16
9 9 4
011
I. u./ gram 60 100 80
1936-
Sample No. Daily dose 24
Me. 12, 18
7
of rats
Vitamin Din oil
12
gram 120
No.
I. u./
Nine samples of canned brisling were examined, Eight had been already tested in the raw and smoked state, and one sample was 8 years old. The results are as follows:.
Sample No.
Age of Product
Daily Dose 7,15,30
8yr.
7 4.5 2.5 5 5
3 4 8 12 12"
No. of
Rate
Mu.
Months
X=
32 43 21:42 42,86 32 82
12 1933 8
11 12 3 3
-Vitamin
D ContentIn fish In oil total (calcd.) product I . U./IOO I . U. per gram gram 50 95 1850
In
total oil
30 60 35 50 45
90
110 100
1000 2000 1150 1650 1500
50 40 40
130 145 70
1650 1300 1300
60 130
1936 _...
24 26 27 a Packed
21,35,50 11 3 50 35 3 in aluminum.
22
6
8
The vitamin D content of fish oil from the canned product was calculated by the same method as was used for vitamin A. The vitamin potency of oil from canned brisling varied from 60 to 145 I. U. per gram, averaging 100 to 120 I. U. There is no evidence of destruction of vitamin D as a result of either canning or subsequent storage of the product. The total vitamin D content in canned brisling was calculated to be 1000 to 2000 I. U. per 100 grams of canned product. These results show that brisling is a valuable source of vitamin D; the oil is equal to good grades of cod liver oil in vitamin D content and contains about as much vitamin A as butter
.
Vitamin A in Herring
-1933Sample Vitamin A No. in Oil
-1936Sample No.
I . U./gram 1
3 4 5
13 4 8 2
11 12
1
Fishing District
Ryfylke
7
Hordaland
8 9
b
12 13 14 15 16 17
18 19 20
13/2 l6/2 20/2 21/2 2812 2/3
18/1 22/1 29/1 25/1
10
11
Date of Catch
21 Rogalsnd 22 Rogaland 23 Rogaland 10/2 24 M6re 23/2 Oil determined in whole fish.
if;
18 19 20 21 22 24
30
In
E. V.
%
Gram 1 0.92 0.85 0.78
0:66
..
4.5 3.75
.. ..
177 130 354 177
2:s 3.2
300 216
om.
I . u./ gram of oil 5 664
a t 328 mp
4'160 11:341 5,660
....
...
I. u./
gram of oil
9,600 6,900
3.5 2.42 6.42 3.07 2.25
5,600 3,872 10 272 4:912 3,630
4:64
7.260
....
18.8 19.2 15.1 15.0
.. .. *. ..
35
273 287 284 299 238 315 273
14.3 11.2 15.1 12.4 12.1 13.6 12.1
The vitamin D content of the body oil of winter herring was determined in six samples from the 1933 catch and eleven samples from 1936. The vitamin D content is rather constant, the figures varying between 90 and 150 I. U. per gram of fat:
14:2 15.5 13.7 15.7 14.8 13.7
1937 32.7 32.0 31.7
270 247 260
13.1 14.8 12.8
32.7 34.2 33.1 33.3
258 286 271 277
10.8 10.6 10.04 12.6
1937.Vitamin A i n Oil
I . U./gram 18
32 38 9 16 16 12 Ca. 5
19 20 21 22 23 24
Oil Content
In raw In smoked Length
Weight
fillet
Cm.
@rams
%
1933
...
34
i4i
.. .. .. ..
.. 1936 31 34 28 34
35
11/1 12/1 21/1
1957
&L% Fish Liver
Vitamin D in Herring
No.
Ca. 2 3-4 Ca. 2 2 2 2
Ryfylke
Hordaland Hordaland Fjordane
Sample No.
Spectrographic
&%F& 1 %Detn. Reaction
Fat
13.4 12.0 12.8
Sample
TABLE111. SUMMARY OF HERRING SAMPLES Sample No.
Weight
of Liver
12.7 12.7
--
Vitamin A i n Oil
I . U./gram 7 8 9 10
The vitamin A content proved to be highest at the beginning of the season. I n ten samples of smoked fish tested, the vitamin A content was found to have decreased very little. Vitamin A was also determined in ten corresponding samples of canned kippered herring; traces of vitamin A were found in all of them. The accuracy of the chemical method for small amounts of vitamin A is, however, not great. The results seem to indicate destruction of vitamin A during the canning process. Biological assays are a t present being carried out. Notevarp (16) gave values for vitamin A in the body oil of winter herring of 10 to 50 I. U. per gram. These figures are in good agreement with the present results. The vitamin A content of the liver oil of winter herring was also examined with the following results:
The numbers of the oil samples correspond to the fish from the same lots as are given in the two preceding tables. The agreement between the antimony trichloride and the extinction coefficient methods is quite satisfactory. The results show that the herring liver oil is 250 times as potent in vitamin A as the body oil. This finding has been confirmed by the Schmidt-Nielsens (20) and by Ahmad and Drummond (1). During the preparation of kippered herring the fish is eviscerated. I n sample 30 we examined the viscera (which contains the liver), and its 3 per cent fat content showed a vitamin A potency of 768 I. U. per gram of oil. Therefore, the vitamin A content of oil from herring viscera equals that of a good grade of cod liver oil. Lunde, Kringstad, and Vestly (9) determined vitamin A in the total oil of fat herring and found the content to be 22 I. U. per gram, that of the body oil, 5 I. U., and that of the liver oil, 250 I. U. The total fish oil of small herring caught in September, 1933, contained 23 to 60 I. U. per gram of oil. The mixture of oils in canned herring (fish oil plus olive oil) was found to have from 6 to 11I. U. per gram, amounting to 180 to 330 I. U. per 100 grams of the total canned product.
Table I11 gives a summary of the samples of winter herring examined. The fat content has a tendency to decrease with the fishing season. The vitamin A content of the body oil of the raw fish varies widely:
2 3 4 5 6
VOL. 29, NO. 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
1174
9:s 8.7 11.8 9.0 10.5
... ...
... 223 280 286 150
-
fish
%
10.1
1933 Sample No. Daily dose
MU.
.. .. a .
13:3 12.2
..
15 20 30 15: 20: 25 15,30 25,40 1 5 25 15: 30
No. Vitamin of D in rats oil I . u./ gram 140 10 150 10 14 100 90 10 110 10 13 140
.-
1936
Sample
No. Daily dose 7 8
9 10 11 12 13 14 15 16 17
10 5 10, 1 5 10: 15 12 10 15 10: 15 10 15 10: 15,20 10 14 10' 15 10: 15
No. Vitamin of Din rats oil I . u./ 4 12 8 4 8 8
8 18 8 12 8
gram 100 130 120
120 140 135 125 105 145 145 145
-
OCTOBER. 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Smoked (kippered) samples from the 1936 catch were also examined with the following results: S*mde
Dsily DOae
NO.
Vitamin D i n Oil I . Ii./ararn ." 135 115 140 125 145 130
No. of
Rats
MO.
12 13 14 15 17
8 12 12 S
a
10
The results show that the smoking process does not have any influence on the vitamin D content. The vitamin D content of the canned product was also determined after different times of storage. The figures varied from 70 to 140 I. U. per gram of oil: ssrnpie storaae No. Period Months
Daily Dwe
No. of Rats
MY.
Vitamin D Content I . U.fLO0 I . u./ mama wnm oil herring
1933
Xo 1 5 51
32
1.5
1 1
27.55 22.44 20,40 20,40
6 8 8 7
70 135
16 31
130 80 130 130 140 95
70 80
1400 1720 840 960
1930 12
3 6
11.15
10 15. 20, 25 10: 1.5 2 10 14 1 10: 15 17 6 10. 15 Padred in an alnminum can.
l3 14 15
6
a vitamin D potency equal to that of a good grade of cod liver oil. Since kippered herring contains about 12 to 13 per cent of oil (IO), the canned product is a food with a high nutritional value and a high vitamin D potency.
~
10.15 10,13 10, 13 10, 14 10 15 11: 16
10
1175
la
18 21 20
1850 1240 1780
2040 2070 la00
Thus the vitamin D content was not affected either by the canning process or by storage. It is apparent that the oil of canned kippered herring has
Literature Cited Ahmad and Drummond, Biochem. J.. 24, 27 (1930). Bills. J . Bid. Chcm.. 72, 751 (1927). Blix. Rydin, and Englund, Updala LlikereJoren. For/,., 40, 175 (1984). Broeklesby and Donstedt, Can. Chem. Met.. 14, 29 (1930). Chevallier and Chitbre, Bull. mc. d i m . Diol., 16, 1451 (1934). Chevallier, Guillot. snd Chabrc, Ibid., 15, 358 (1933). Eckelen, van. Emmeric, Julius, and Wolff. Proc. Acad. Sci. Amateidam., 35, 1337 (1932). Lundc, Tids. Hemetikind., 22, 138 (1936). Lundc, Kringatad. and Vestly, Zbid., 19, 305 (1933). Lundo and Methiesen. Zbid, 17, 176 (1931). Ibiii., 19, 87 (1933). MoWslter. Biochem. J., 28, 472 (1934). Manning, Nelson, and Tollo, U. S. Bur. Fisheries, Znoestigotionol Zlepi-".,3 (1931). Matuko, Z. Untersuch. Lebensm.. 67, 172 (1934). Noison and Manning. h n . Ex". CN~M., 22, 1361 (1930). Notwarp, Ti&. Kjemi Berpe.%en,25.49 (1937). Poulsson and IAvonskjoId, Biochem. J., 22. 135 (1928). Sahoonort and Sohieblich, 2. Unleruuch. Lehemm.. 68,409 (1934). Sohmidt-Nielsen, Astad, Flood, Stone, and Sarensen, Kgl. Noiske Videnskab. Selsknbs Sizrilter, 1935, 40, Schmidt-Nielsen. Signo, and Schmidt-Nielscn, Sigval, Kgl. Norske Vidmskob. Selsk. Forh., 1, 45 (1927); 2, 44 (1929);
". . .~~".,",. 9 76 ,10)9m
Shrmn and How, Can. J . Reseal.& 813, 93 (1935). Supploe, I ~ DENS. . CHEM.,29. 190 (1937). Toile and Nelson. Zhid.. 23. 1066 (1931). Trucsdnil and Ciilbertson. Ibid., 25, 563 (1933) R ~ C B ~ Y June E D 23. 1T317.
