TECHNICAL NOTE NO. 6--VITAMIN-A POTENCIES OF LIVER OILS
OF BERING SEA COD AND FLOUNDER

Oil and vitamin-A analyses were made of the livers of certain species of
Bering Sea cod and flounder. The fish were obtained by the Exploratory Fishing
and Gear Development Section of the Branch of Commercial Fisheries while con-
ducting exploratory fishing in the northern Bering Sea area during June-July 1949
(Ellson, Powell, and Hildebrand 1950). The livers of the following species of
fish were analyzed: Pacific cod (Gadus macrocephalus), flathead sole or flounder
(Hippoglossoides robustus and H. elassodon), lemon sole or Alaska plaice (Pleu-
ronectes quadrituberculatus), rock sole or flounder (Lepidopsetta bilineata),
and yellowfin sole or mud dab (Limanda aspera).

Table 1 Data on the Type of Fish, Sex, and Number of Fish Examined, and Average Value of the Measurements Obtained on Fish
Length, Fish Weight, Liver Weight, Cil Concentration in Liver, and Vitamin-A Potency of Liver Oil

The livers were analyzed by the "shaking method," using ethyl ether as the solvent (Anonymous 1947). The data are reported in Tables 1 and 2.

The livers of the flathead sole, lemon sole, rock sole, and yellowfin sole were, on the average, less than an ounce in weight and contained only a small amount of oil, which was of a relatively low vitamin-A potency. Such livers are of only marginal value.

Oil concentrations and vitamin-A potencies of the cod livers reported here are similar to those of livers taken commercially in 1947 from fish caught in the Bering Sea off the Alaska Peninsula (Sanford and Nilson 1949). Northern Bering Sea cod livers may, therefore, be of potential commercial value. This conclusion, however, is contingent upon the price of vitamin A rising at least to the 1947 level.

Data on the Lowest and Highest Values Obtained in the Measurement of Fish Length, Fish Weight, Liver
Weight, Oil Concentration in Liver, and Vitamin-A Potency of Liver Oil

Vitamin-A potency
of liver oil
Low

"Spec" units "Spec" units

Oil concentration

High
Percent

High

1/Fish length was the distance from the tip of the nose to the fork of the tail. 2/2,000 x e (1 percent, 1 cm., 328 mmu., isopropanol, whole oil).

}

LITERATURE CITED

ANONYMOUS

1947. PRELIMINARY PROCEDURES FOR THE ANALYSIS OF VITAMIN A IN FISHERY BY PRODUCTS. COMMERCIAL FISHERIES REVIEW, VOL. 9, NO. 1, (JANUARY) PP. 40-2.

ELLSON, J. G., POWELL, DONALD E., AND HILDEBRAND, HENRY H.

1950.

EXPLORATORY FISHING EXPEDITION TO THE NORTHERN BERING SEA IN JUNE AND JULY 1949.
U. S. FISH AND WILDLIFE SERVICE FISHERY LEAFLET 369.

SANFORD, F. B. AND NILSON, H. W.

1949. VITAMIN A AND D POTENCIES OF THE LIVER OIL OF PACIFIC COD. COMMERCIAL FISHERIES REVIEW, VOL. 11, NO. 5, (MAY) PP. 13-5.

--F. Bruce Sanford, Chemist,

John A. Dassow, Chemist,
Ernest F. Dietrich, Laboratory Aide,
Fishery Technological Laboratory,
Seattle, Washington.

INFORMATION SOURCES FOR STUDENTS OF
COMMERCIAL FISHERIES

Fishery Leaflet 362, Information Sources for Students of Com-
mercial Fisheries, is a 20-page publication designed to show the
student various means of obtaining information on the commercial
fisheries of North America. It is not meant to be a complete bib-
liography--only the principal contributions or bibliographies are

listed.

References in this publication are listed under the following major categories: Agar; byproducts; canning; cookery; directories; employment; fish and fisheries; freezing; gear; libraries; marketing; oils, rancidity, antioxidants; salting; sanitation; smoking; spoilage; statistics; technical journals; trade journals; visual aids; and vitamin oils. Items which are recommended as basic sources are indicated.

By R. Paul Elliott

--Fishery Leaflet 362 (January 1950)

TECHNICAL NOTE NO. 7--RESULTS OF SOME TESTS WITH

FROZEN LOBSTERS AND LOBSTER MEAT

INTRODUCTION

Very little information is available regarding the freezing characteristics of lobsters and lobster meat. Although the quantity available for freezing would undoubtedly be quite limited due to the heavy demand for live lobsters, it may be desired at times to freeze this product on a small scale. This is evident by the inquiries on freezing of lobsters received by the Fish and Wildlife Service from locker plant operators, and manufacturers and owners of home freezers.

With this in mind, a limited study of the storage of frozen lobsters and lobster meat was made. Since the work was restricted to only a comparatively small number of samples held at only one storage temperature, it should not be construed that the results are conclusive. Possibly other methods of preparation and lower storage temperatures would alter the findings considerably.

PREPARATION OF SAMPLES

Live lobsters and freshly-cooked lobster meat were obtained and prepared for the tests in Gloucester, Mass. Five lots were prepared for freezing, as follows:

1. Whole live lobsters. These are designated later in this
report as the "uncooked" sample.

2. Whole cooked lobsters. These were live lobsters boiled
for 16 minutes in salted water (1 tablespoon of salt to
1 quart of water).

3. Whole cooked lobsters. Similar to (2), which were frozen
in blocks of ice after one month of storage at 0° F.

4. Cooked lobster meat packed without liquid in half-pound
tin cans and hermetically sealed.

5. Cooked lobster meat packed in 1 percent brine in half-
pound tin cans and hermetically sealed.

All samples were frozen in circulating brine at a temperature of approximately 0° F., followed by storage in a room at the same temperature. The whole lobsters were given an ice glaze to retard desiccation.

It had been planned to freeze several cooked lobsters in blocks of ice at the time the samples were being prepared in order to ascertain whether a minimum of desiccation during storage would prevent changes in the texture of the meat. Because of certain difficulties this was not done at the time of freezing but was done a month later (Lot No. 3). The samples were kept ice-glazed during this interval.

All of the lots were shipped with dry ice in an insulated container to the Service's Fishery Technological Laboratory in College Park, Md., and were received in a frozen condition. The whole lobsters were then reglazed and packaged individually in heavy metal foil wrappers. All samples were held in storage at 00 F.

At monthly intervals, samples from each lot were removed from frozen storage and allowed to thaw at room temperature. Those that were uncooked were thawed, then boiled in salted water for 16 minutes, and cooled before being tested. The meat was picked from the whole lobsters and cut into pieces for palatability tests. The meat from fresh-cooked live lobsters was used as controls. All samples were designated by a code unknown to the judges at the time of testing. Members of the laboratory staff, accustomed to making taste tests, served as judges. Scores were based on the appearance, flavor, and texture of the lobster meat. A score of 85 or over is considered satisfactory.

RESULTS AND DISCUSSION

The palatability scores obtained in the tests are given in Table 1. The frozen uncooked lobsters consistently received a satisfactory and relatively high score

Neither of the lots of frozen picked meat stored too well. The failed to receive an accept

meat that was frozen without added liquid (dry pack)
able score during any month of the storage period. The flavor of the meat was ob-
jectionable and the texture was described as watery and spongy. The meat frozen
with added liquid (brine pack) received somewhat higher scores but in general it
could hardly be considered satisfactory either. It is doubtful if this pack has
very much in its favor over the dry-packed product.

In all lots, the claw meat was sometimes found to have somewhat of an off flavor, even though the body meat was all right.

Considerable variation was found in the scores for the fresh controls. This may have been due to the manner in which the live lobsters were handled.

While the frozen uncooked whole lobsters received the highest palatability scores, there is one other factor that must be considered. After cooking the whole

lobster, the meat was found to stick very tightly to the shell and was difficult
to remove without breaking it into small pieces. This may or may not be objection-
able, depending upon the attitude of the consumer, since the meat is very often cut
into smaller pieces before being used.

Note: A UNITED STATES PATENT HAS RECENTLY BEEN GRANTED WHICH DEALS WITH THE FREEZING OF LOB-
STERS. IT IS CLAIMED THAT THE DIFFICULTIES ENCOUNTERED IN REMOVING THE MEAT FROM THE
SHELL OF LOBSTERS FROZEN ALIVE OR RAW AND THEN COOKED MAY BE OVERCOME BY A BRIEF HEAT
TREATMENT PRIOR TO FREEZING. THIS TREATMENT CONSISTS OF AN IMMERSION OF THE LOBSTER
IN BOILING WATER FOR AN INTERVAL OF NOT LESS THAN 15 SECONDS NOR MORE THAN 5 MINUTES,
DEPENDING ON THE SHELL THICKNESS. THE HEATING PERIOD SHOULD BE ONLY OF SUFFICIENT
DURATION TO PRODUCE A COOKING OF THE SURFACE OF THE MEAT NEXT TO THE SHELL BUT NOT TO
COOK THE MEAT BELOW THE SURFACE. A HEATING PERIOD OF ABOUT 1-1/2 MINUTES IS SAID TO
BE SUFFICIENT FOR A ONE POUND LOBSTER. AFTER HEATING, THE LOBSTER IS COOLED AND QUICK
FROZEN (U. S. PATENT NO. 2,501,655 "FROZEN LOBSTER MÉTHOD, PTD. MARCH 28, 1950).

Illustrator--Gustaf T. Sundstrom

Compositors--Jean Zalevsky, Carolyn Wood, Betty Coakley

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