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DEPARTMENT OF THE INTERIOR
HAROLD L. ICKES, Secretary
FISH AND WILDLIFE SERVICE
IRA N. GABRIELSON, Director
Applications for FISHERY MARKET NEWS, which is mailed free to members of the fishery industry and allied interests, should be addressed
to the Director, Fish and Wildlife Service, United States Department of the Interior, Washington 25, D. C.
of the five species of Pacific salmon, only pink salmon (Oncorhynchus gorbuscha) is not generally frozen commercially. The freezing preservation of this species has been limited because of the development of discoloration and rancidity of the frozen fish after comparatively short storage periods. If a successful method of storing it in the frozen state could be developed, it is believed that a large market would be available. The canning process causes the color of pink salmon to fade from the deep pink of the fresh flesh to a pale pink, Freezing, however, causes no change in the normal attractive color, yielding a product having an appearance comparable to the more highly prized chinook salmon.
Very little work has been done on the freezing of this fish, Stansby and Harrison (1942) found that frozen pink salmon lost its flavor after one month's storage, and that in only two months' time, rancidity and discoloration had developed to make the fish almost unsalable. After four months, all samples were definitely rancid, Brining the fish not only did not inhibit rancidity, but actually accelerated its development.
In a recent report (1944) from the Fishery Products Laboratory in Ketchikan, Alaska, it was found that commercially prepared pink salmon steaks were definitely yellow along the skin edges after two or three months in storage at 0° F., and the flavor was slightly rancid, whole glazed fish, however, kept for seven or eight months, and five-pound blocks of iceglazed steaks could be stored for at least six months. Ice-glazed steaks in vacuumized cryovac latex bags were still good after 12 months.
In order to store frozen pink salmon satisfactorily, it is necessary to delay the rapid oxidation of the oils. Past experiments in this laboratory have indicated that antioxidants and oil dips had very little effect in retarding rancidity, but that when air was kept away from the fish, considerable improvement in keeping quality resulted. Accordingly, a series of experiments was conducted to study various methods of keeping the fish out of contact with air.
For control samples (A), duplicating the usual commercial practice, steaks were individually wrapped in a moisture-vapor-proof cellophane paper and packed into five-pound fillet boxes.
Two sets of samples were packed in one-half pound flat tinplate cans and sealed under 25 inches vacuum, One of these (B), was packed without water and to the second (c), was
C added sufficient water to cover the salmon steaks.
Since, at the present time, some locker-plant operators are recommending that their patrons freeze fish covered with water in glass jars, tests were made to determine the effectiveness of this method. Pieces of fish fillets were packed into two lots of glass jars. The first (D), was sealed immediately, while before sealing the second (E), just enough water म
Chemist, Seattle Fishery Technological Laboratory.
was added to cover the fish and still leave a head space of about one and one-half inches. In no case did the jars break during the freezing or storage periods.
An effective means for preventing oxidation of fish fillets or steaks consists of covering them with an ice glaze and then wrapping in moisture-vapor-proof paper or otherwise protecting the glaze from evaporation. One series of pink salmon steaks was handled by a recently developed simplification of this procedure (F). The steaks were packed into 5-pound waxed-fibreboard fillet boxes, which had two 3/4-inch holes punched in each end. Each package was placed in a freezer until the contents were frozen, and then the entire box was immersed in water, which formed a glaze around the fish--the excess water running out of the holes.
All samples were stored in a refrigerated locker such as is available to the general public, and examinations were made periodically. The storage temperature was approxinately 100 F. but varied considerably. The fish were examined in both frozen and thawed condition; thawed samples were wrapped in parchment paper, cooked in boiling water for twenty minutes, and examined organoleptically.
At the end of seven weeks, all samples were in good condition except sample (A) (control in cellophane) where the steaks were faded in color and were slightly rancid. Top steaks of sample (D) (glass jars) also had begun to fade and become rencid. Sample (f) (glazed sample) was in fair condition, but was also beginning to show signs of incipient deterioration.
After three months, sample (A) (control in cellophane) was definitely rancid while top slices of (D) (glass jars) were slightly rancid as was sample (F) (glazed sample). Both of the last two were rancid at the 5 months' examination period,
Samples (B) (vacuumized tin cans) and (c) (vacuumized tin cans with water) were still in very good condition at the end of nine months' storage, In sample (C), there seemed to be a general bleaching, and the flavor was not quite as good as in those cans which did not contain water. Top pieces of (E). (glass jars with water) showed slight rusting while the lower pieces had faded to a pale peach color. The fish was still edible although the flavor was flat. In sample (D) (glass jars), top pieces showed a good deal of rusting. Bottom slices, however, had good color, showed no visible signs of deterioration and tasted almost as good as the vacuum packed samples. Results of these storage tests are given in Table 1.
Table 1. Summary of Storage Tests of Frozen Pink Salmon
L en Description
t b of Stora se
9 Months A. Cellophane-wrapped Color fading; be- Definitely discolored; Rancid; appearance Darkened; blood steaks packed in coming yellow; odor-rancid; flavor
spots very brown. 5# fillet boxes. very slightly rancid,
Large amount of rancid,
rancid, B. Steaks packed in Perfect condition, Flavor normal; ap- Texture normal; ap- No deterioration; vacuumized tin
flavor good. cans.
flavor-good (best). C. Steaks, covered Perfect condition. Flavor normal; ap- Texture soft; ap- General bleaching with water, and
pearance almost of steaks and packed in vacu
normal; flavor- sof tening. Flavor umized tin cans,
slightly flat. D. Fillets, packed Top slices be- Top slices slightly Appearance fair ex- Top pieces rancid
in pint glass ginning to fade rancid; also dis- cept top slices with good deal of jars. and be come rancidd colored,
which were very
rusting. Bottom much discolored, slices of good Rancid,
color. No visible signs of rancidity. Almost as good as
vacuum packed, E. Fillets, covered Good condition; Flavor normal; ap- Color good; flavor Top pieces slightly with water, natural color. pearance normal.
normal but not as rusting; lower packed in pint
good as tin packed. piece faded; pale glass jars.
flavor-flat. F. Glazed steaks Fair condition; Slightly rancid fla- Rancid; appearance Very rancid
odor. packed in 5# beginning to vor; discolored
Rusting around fillet boxes, fade. yellow spots-darken
sides of steaks; ing of dark areas,
light yellow spots, Conclusions--Although ordinary commercial methods of freezing and storing are not suitable for pink salmon, if this fish is vacuum packed it will keep in good condition in frozen storage for at least nine months.
It is possible that glazed fillets or steaks might be stored with some degree of success since such samples keep better than those wrapped in cellophane. Probably a glaze heavier than that used in the present experiments would be more effective, and in any case, the glazed block of fish should have some additional protection such as a waxed carton.
For freezing fish for home refrigerator locker use, reasonably good protection is afforded by packing the fish in glass jars, just barely covering the fish with water, but leaving a head space of about one inch, fastening on a tight lid and freezing. Pink salmon treated in this way will keep in good condition for about four months under average locker storage condition.
LI ERATURE CI TED
Fishery Products Laboratory, Ketchikan, Alaska, 1944. Freezing Studies on Alaskan Fish with Particular Reference to the Pink Salmon. Unpublished manuscript.
Maurice E. Stansby and Roger W. Harrison, 1942. Preliminary Investigation of Methods for Freezing and Storing Fillets of Some Pacific Northwest Fish. Special Scientific Report No. 15, U. s. Fish and Wildlife Service, Washington, D. C.
STUDIES ON THE ICING OF FRESH-COOKED AND PEELED SHRIMP
By E. F. Kapalka and S. R. Pottinger*
Due to restrictions on the use of metal (particularly tinplate) containers for the packaging and shipping of fresh-cooked and peeled shrimp, large quantities of this product have been packaged in fibre or paperboard containers. Although these packages have proven to be reasonably satisfactory from the standpoint of rigidity and resistance to crushing when packed in melting ice, there has been some question regarding the rate of cooling and maintenance of proper temperatures in the shrimp meat packed in these containers, When fresh-cooked and peeled shrimp are shipped under refrigeration to distant markets, the temperature of the product must be maintained at a low level to preserve the delicate flavor and insure sanitary quality. Therefore, studies were conducted to determine the rates of cooling of shrimp meat in various types of containers when iced under conditions similar to those which may be encountered in commercial practice.
Five-pound size containers of types now used by the industry for the packaging and shipping of fresh-cooked and peeled shrimp were employed. Containers used were:
1. Chemically-treated and lacquered blackplate--cylindrically shaped, having a capacity
of one gallon,
cover, and having a capacity of five pounds of shrimp meat.
Experimental Results--Five pounds of cooked and peeled shrimp. were placed in each of of the three types of containers and iced under varying conditions. Temperature changes occurring within the containers were followed by means of thermometers.
In the first series of tests, the containers were filled with shrimp meat at an initial temperature of about 80° F. and kept thoroughly surrounded with melting crushed ice throughout the test period. The rate of cooling was somewhat retarded in the fibre box, as shown in Table 1, and Figures 1 and 2. The walls of this container are considerably thicker than those of the other types of containers.
Technologists, stationed at the Technological Laboratory, College Park, Md. 1/ In the Gulf States, "cooked and peeled shrimp" usually are prepared by removing the heads and shells
and boiling the raw meats in a weak brine; the sand veins may or may not be removed. The cooked meats are sold either as a fresh-cooked product, in which case they may be eaten without further preparation, or they are further processed by freezing.
Table I-- Temperature of Cooked and Peeled Shrimp Packed in Containers
and Completely Surrounded with Crushed Ice Location of
Initial Temperature 50°F. Thermometer
elapsed Me tal can Fibre cylinder Fibre box Metal can Fibre cylinder Fibre box
OF. Center of container 3.5
35.5 14-inch from container 3.5
35.5 Inside surface of
Imia mia min
Since in the first series, the temperatures of the meats in each of the containers were still quite high after 3 hours' refrigeration, the effect on the rate of cooling of preliminary chilling of the meat was studied in a second series of experiments. Shrimp meat, pre-chilled to about 50 F., was placed in the three types of containers and iced as before. The data, also in Table 1, show that the meat in each of the containers reached a safe temperature in about 3 hours.
Two other series of tests were conducted in which only one-half of each container-including top, bottom, and sides--was surrounded with crushed ice, leaving the other half exposed to air temperature. In one series, shrimp meat at an initial temperature of about 800 F. was placed in the containers, and, in the other series, the meat was pre-chilled to about 500 F. before packing. The results are shown in Table 2. The differences in the rates of cooling in the three containers were not so marked in the series in which the shrimp meat had been pre-chilled. When warni shrimp meat was used, however, the cooling rate was much more rapid in the metal containers
Table 2--Temperature of Cooked and Peeled Shrimp Packed in Containers
and Only Partly Surrounded with Crushed Ice Location of
Initial Temperature 500F Thermometer
elapsed Me tal can Fibre cylinder Fibre box Metal can Fibre cylinder Fibre box
OF. Center of container 3.5
39 Center of iced portion 3.5
41 of container
36.5 37.5 Center of uniced 3.5
70 portion of container 7
59.5 Inside surface of 3.5
35.5 38.5 iced portion of 7.
34.5 container Inside surface of 3.5
48 uniced portion of
Discussion--Although fish and shellfish are generally shipped with a sufficient quantity of ice to provide adequate refrigeration until the destination is reached, there may be times when the containers are improperly packed and the contents remain at elevated temperatures for excessively long periods of time. Sometimes, in an effort to fill an order as quickly as possible, the shipper may be tempted to place warm shrimp meat directly in the shipping container, ice it, and then ship it out immediately, with the expectation that the temperature of the meat will drop rapidly enough to prevent spoilage. Unfortunately, the relatively large air spaces between the individual shrimp meats in the containers are poor conductors of heat and, therefore, seriously retard the cooling process.
The results of the experimental work conducted on the rate of cooling of warm shrimp meat packed in the three types of containers and kept surrounded and covered with crushed ice, indicate that the temperature in the metal can decreases at a slightly greater rate. Even in the metal container, however, it requires at least seven hours to reach proper refrigerating temperatures,
À proper storage temperature, irrespective of the type of container, was obtained much more rapidly by quickly pre-chilling the shrimp meat to 50° F. before packaging, and then thoroughly icing the package. Pre-chilling can be accomplished very simply by dipping the unpackaged shrimp meat in cold brine or holding it in a refrigerator.
When the containers are only partly covered with ice, the rate of cooling is considerably slower in the fibre containers than in metal. Metal being a better conductor, transfers the heat from the un-iced portion of the containers. While ample quantities of ice always should be used regardless of the type of container in which shrimp meat is packed, very special attention should be given the icing of fibre packages, particularly in warm weather when rapid melting of ice will occur. As the cost of ice is a minor factor in the total cost of a shipment of shrimp, more space in the shipping container should be allowed for ice and more ice should be used.
DRILL SAMPLING DEVICE FOR FISH LIVERS
I. CONSTRUCTIONAL DETAILS
L. G. McKee, F. B. Sanford, and G. C. Bucher*
Since publication of the article "Preliminary Report on a Drill Sampling Device for Fish Liversť/," constructional details have been modified to improve the operation of the sanpler, and considerable experience in its use has demonstrated that the device is practical for commercial adaptation. Another report2) gives instructions and precautions for most effective use of the sampler described here,
The sampler is designed specifically for use with livers in the standard five-gallon can employed on the Pacific Coast. Where the livers to be sampled are in containers of another size, appropriate modifications in the length and possibly other details of the sampler will have to be made. The design described here has given good results on fresh, unfrozen livers, and it will work well with soft-frozen livers. Sampling of hard-frozen livers, however, would require a more powerful motor.
The sampler (Figures 1 and 2) consists of five essential parts:
1. Drive unit.
4. Sample bottle to receive cores,
of liver can,
The drive unit is a standard model, 4 inch, heavy duty, electric drill with a rated speed of 1750 R.P.M. This type drill is particularly well adapted for use with the sampler because there is a convenient handle by which the device may be manipulated. Also the hous
Technologist and Chemists, respectively, Seattle Fishery Technological Laboratory. 1/Charles F. Shockey and F. Bruce Sanford, Fishery Market News, Vol. 6, No. 5, May 1944, pp. 9-10, /"Drill Sampling Device for Fish Livers," II. INSTRUCTIONS FOR USE. F. Bruce Sanford, Glenn C. Bucher,
and Maurice E. Stansby. This issue, page 9.