ADVANTAGES AND DISADVANTAGES The greatest advantage of the electrical depth telemetering system is its simplicity and practicability. Since it is a direct-reading instrument with a simple offon range selector switch and line control rheostat to set, no specially-trained operator is needed. Likewise, no special handling on deck is required as the sensing unit is attached as a permanent part of the fishing gear. Being electrical, the system is not affected by distance, directivity, water currents, wake, ambient sea noises, etc., as are acoustic telemeters. The 225-fathom range can be increased with the installation of a suitable pressure potentiometer, and recalibration. Use of the system on bottom trawls is feasible due to the small size and rugged construction of the sensing unit and housing. Routine maintenance can be performed by relatively unskilled personnel. The accomplishment of connecting an electrical circuit from the pilothouse of a fishing vessel to a trawl deep beneath the ocean surface makes possible the transmission of other types of desirable information to the vessel operator. Constant monitoring of water temperature at trawl depth is possible with the addition of a small thermistor inside the pressure housing of the sensing unit, similar to the S-T-D used by oceanographers (Collias and Barnes 1951). Ink pen recordings of depth and temperature can be made if permanent records are desired. Also, graphic presentation of telemeter depth readings onto the echosounder recording paper used during fishing operations is entirely practical. Even some form of automatic or adjustable controls on the fishing gear could be installed if found to be desirable and practical in the future (Fryklund 1956). Apparent possible disadvantages of the electrical depth telemeter are few and may prove to be of minor importance with continued use of the system. Splicing the electrical trawl cable is more difficult and time-consuming than splicing standard cable used on fishing vessels. A 50-foot long-splice is required, which was found to be not unduly difficult after some experience. The 3,000-foot cable in use on the John N. Cobb is made up of two sections which were spliced together by two staff members in approximately two working days. Present cost of the electrical cable is roughly 60 percent higher than the cost of regular plow steel trawl cable, but this cost differential cannot be properly evaluated until the life expectancy of a new cable is determined through actual service over an extended period of time. LATEST REFINEMENTS Certain refinements to the electrical telemeter hook-up were made on subsequent field trials to provide more accurate lead-line depth when midwater trawling very near the bottom. The depth sensing unit was moved from in fig. 12). This necessitated use of Some breaking of the electrical conductors in the core of the trawl cable was experienced during later bottom trawling operations. This was caused by the stresses created as the electrical trawl cable passed around the standard size 9-inch diameter towing blocks (see fig. 2). The use of specially-design ed and fabricated 20-inch diame- I Fig. 14 Large Block--20-inch diameter, aluminum --used with electrical trawl cable. ter aluminum trawl blocks has apparently remedied this condition (see fig. 14). LITERATURE CITED Barraclough, W. E., and Johnson, W. W. 1956. A New Midwater Trawl for Herring. Bulletin No. 104, Fisheries Research Board of Canada, Ottawa. Collias, E. E., with Barnes, C. A. 1951. The Salinity-Temperature -Depth Recorder. University of Washington Oceanographic Laboratories, Seattle, August. Dow, Willard 1954. Underwater Telemetry: A Telemetering Depth Meter. Woods Hole Oceanographic Institution Ref. 54-39, Woods Hole, Mass. Fryklund, Robert A. 1956. Controllable Depth Maintaining Devices. U. S. Patent Office publication, Patent No. 2,729,910, Washington, D. C., January 10. Richardson, I. D. 1957. Some Problems in Mid-Water Trawling. World Fishing, vol. 6, No. 2, John Trundell, Ltd., London, Feb ruary. Smith, Keith A. 1957. An Experimental Air-Pressure Depth-Meter for Use with Midwater Trawls. Commercial Fisheries Review, U. S. Fish and Wildlife Service, Department of the Interior, Washington 25, D. C., vol. 19, no. 4 (April), pp. 6-10. (Also Sep. No. 474.) Stephens, F. H. Jr., and Shea, F. J. 1956. Underwater Telemeter for Depth and Temperature. Special Scientific Report.- Fisheries No. 181, U. S. Fish and Wildlife Service, Department of the Interior, Washington 25, D. C., June, 15 pp. FOOD FOR FITNESS - A DAILY FOOD GUIDE Food for Fitness A Daily Food Guide, Leaflet No. 424, compiled by the Institute of Home Economics, U. S. Department of Agriculture, which supercedes The Basic Seven is now available to the public. In this guide, the main part of the daily diet is selected from these four broad groups: Milk Group: Some milk for everyone. Children 3 to 4 cups; teen-agers 4 or more cups; adults 2 or more cups. Meat Group: Two or more servings of beef, veal, pork, lamb, poultry, fish, or eggs. Alternates may be dry beans, dry peas, and nuts. Vegetable Fruit Group: Four of more serving including: A citrus fruit or other fruit or vegetable important for vitamin C. A dark-green or deep-yellow vegetable for Vitamin A--at least every other day. Other vegetables and fruits including potatoes. Bread-Cereal Group: Four or more servings of bread and cereals that are whole grain, enriched, and restored Choose at least the minimum number of servings from each of the four food groups. Make choices within each group according to suggestions given in the leaflet. Choose additional foods to round out your meals both from foods in the four groups and from foods not listed in these groups. Try to have some meat, poultry, fish, eggs, or milk at each meal. Leaflet No. 424 is sold for 5 cents a copy by the Superintendent of Documents, U. S. Government Printing Office, Washington 25, D. C. COLOR AND QUALITY OF CANNED GULF OF MEXICO By Arnold W. Tubman* and Lynne G. McKee** ABSTRACT Both color (Munsell value attribute) and flavor score of canned yellowfin tuna from the Gulf of Mexico became less desirable with increasing weight of the fish from which the product was made. The dominant factor controlling quality is the weight of the fish and not one or more of the experimental handling variables studied. On two successive years, yellowfin tuna caught and landed by the U. S. Bureau of Commercial Fisheries exploratory fishing vessel Oregon were shipped frozen to the Fishery Technological Laboratory, College Park, Md., for canning. The first shipment consisted of 31 yellowfin landed in July 1956; the second shipment consisted of 8 yellowfin landed in August 1957. The Gulf of Mexico tuna industry was a new industry in 1956. Yellowfin tuna, the principal catch, had not, prior to that year, been critically examined in the canned state and the results publicly reported. Accordingly, advantage was taken of the availability of the tuna landed by the Oregon. The purpose of the present work was to can the yellowfin tuna in a commercial manner, note the color and general acceptability of the pack, and note also whether these factors were related to any observable characteristics of the fish. PRECOOK TIME AT 216° F. IN HOURS w WEIGHT OF WHOLE FISH IN POUNDS Fig. 1 Relationship of precook time at 216° F. to the weight of the whole frozen fish. PROCEDURE After the frozen tuna were received at the laboratory, they were wrapped individually in waxed freezer paper, overwrapped in burlap, and stored at 3 F. in commercial cold storage. The first shipment of 31 fish was not canned until 8 months after receipt; the long delay was necessitated by the fact that canning equipment had first to be installed at the laboratory. The second shipment was canned within a month of receipt. Fish were removed from cold storage as needed, thawed overnight in fresh water, and precooked the following day at 216 F. Owing to the comparatively large size of the tuna, the fish were sawed into right and left halves before being precooked. The halves were placed exposed meat side down on a wire tray covered with punctured kraft paper. The relationship of the precook time used to the weight of the whole frozen fish is presented in figure 1. The fish, after being precooked, were removed from the retort on the wire trays and cooled at room temperature through the night. The following morning--the second day after the tuna had been placed in the thaw tank--the fish were skinned and cut into loins, and the dark meat was removed. The afternoon of that second day the loins were cut and packed. From each fish, 36 cans of solid pack and 10 cans of flake meat were prepared in 307 x 113 "C" enamel cans. 4 To each can of packed tuna were added 14 ounces of corn oil and one heaping teaspoon (an average of 2.3 grams) of salt. While the tuna meat was being packed, * Mechanical Engineer, Fishery Technological Lab boratory, College Park, Md. **Fishery Products Technologist, Fishery Technological Laboratory, Seattle, Wash. } Division of Industrial Research and Services, U. S. Bureau of Commercial Fisheries. observations were made of the color, texture, degree of honeycombing, and moisture. Immediately after the meat of the tuna was placed in the cans, the cans were steamed under vacuum and then processed at 250° F. for 55 minutes in a retort controlled with a Taylor Instrument system SP-1. The cans were cooled under pressure at 17 psi. and then removed to storage at room temperature. None of the cans was stored less than 1 month before being opened, at which time the vacuum was 13 inches of mercury. The lightness or darkness of the canned meat (Munsell value at 555 millimicrons) was evaluated according to the proposed tuna standards (Federal Register, August 28, 1956) by one of the authors at the laboratories of the Food and Drug Administration in Washington, D. C. Three cans (solid pack) packed from each fish were opened in the prescribed manner, and the meat was compared with neutral reflectance standards (Munsell value scale) under an optical comparator. One can packed from each fish (solid pack) was examined organoleptically at College Park MUNSELL VALUE AT 555 MILLIMIC RONS 10 Fig. 2 Munsell value as related to weight of the whole frozen fish. by three persons. The organoleptic test sample of one can was adequate as the solid pack cans were uniform when packed. Scores of 0 to 100 were given for appear Table 1 Canned Product Evaluation Data on 31 Gulf of Mexico Yellowfin Tuna ance, flavor and texture. A maximum score of 100 was assigned to represent excellence. RESULTS AND DISCUSSION QUALITY CHANGE NOTED WITH INCREASING WEIGHT: The weight of fish was apparently the most important factor in determining the lightness or darkness and the flavor of the canned product. The data in tables 1 and 2 indicate that the meat in all of the cans examined would grade "light meat" according to the proposed standards; that is, the Munsell values determined on the opened cans all were above 5.3 at 555 millimicrons. Yet the data also indicate that some of the fish were of much lower quality than were others. The data in figure 2 indicate an inverse correlation of Munsell value at 555 millimicrons |