Maintaining Quality Of The Catch

Quality is a term that has many definitions, depending on the background and interests of those queried. To some,

Figure 5. Static fishing gear. Crab traps—framed with iron rods and covered with polyethylene rope webbing, crab trays are usually fished on single lines. Size varies according to fishery; ie, small traps are used for blue crab, large traps are used for king crab. Source: Courtesy of Seafood Leader.

Figure 7. Static fishing gear. Inshore lobster fishing—wooden or wire traps with cotton or nylon twine are set on the ocean floor at various depths, either individually or in strings on a line, baited with either fresh or salted fish. Source: Courtesy of Seafood Leader.

Figure 5. Static fishing gear. Crab traps—framed with iron rods and covered with polyethylene rope webbing, crab trays are usually fished on single lines. Size varies according to fishery; ie, small traps are used for blue crab, large traps are used for king crab. Source: Courtesy of Seafood Leader.

Figure 7. Static fishing gear. Inshore lobster fishing—wooden or wire traps with cotton or nylon twine are set on the ocean floor at various depths, either individually or in strings on a line, baited with either fresh or salted fish. Source: Courtesy of Seafood Leader.

Figure 6. Static fishing gear. Weir fishing—rigid poles are driven into the mud bottom to form a heart-shaped configuration; a straight line of poles, leading from the shoreline to the weir, acts as a barrier directing the fish into the weir. Using skiffs, fishermen first seine the catch, then use a brailer or dip-net to collect them. Source: Courtesy of Seafood Leader.

Figure 6. Static fishing gear. Weir fishing—rigid poles are driven into the mud bottom to form a heart-shaped configuration; a straight line of poles, leading from the shoreline to the weir, acts as a barrier directing the fish into the weir. Using skiffs, fishermen first seine the catch, then use a brailer or dip-net to collect them. Source: Courtesy of Seafood Leader.

the measuring of the product degradation by biological factors such as microorganisms or enzymes is the only means of determining quality. To others the aesthetic values that make a product look good are just as important in defining quality. In reality the biological factors determining safety and nutritional values and the physical factors used in a grading system (ie, size and weight uniformity, color, and blemished surfaces) are integrated to mean quality to most people.

The maintenance of quality or the fresh nature of landed seafood depends on many operations from the catching, landing, and shipboard handling to the transporting, storing, processing, and distributing. A biological specimen can only decrease in quality as it travels through the various steps of a commercial venture. Enzymes and microorganisms cause spoilage and degradation that are irreversible. Physical damage not only affects the appearance of a product, but such damage as skin ruptures allow microorganisms to invade the tissue and cause earlier deterioration. Therefore, all participants in the commercial seafood chain are important for maintaining high-quality products.

The Impact of Fishing Methods

Fishing gear is usually designed to give maximum efficiency in catching fish. The total cost of catching a given amount of fish includes vessel cost and operation, fishing gear cost and maintenance, manpower required, and other

Figure 8. Towed or dragged fishing gear. Otter trawling—a method of fishing in which a large wedge-shaped net is dragged along the ocean bottom; an otter door is attached to each side of the net to hold the net open and keep it horizontal. Fish collect in the cod end (the back) of the net. Source: Courtesy of Seafood Leader.

Figure 8. Towed or dragged fishing gear. Otter trawling—a method of fishing in which a large wedge-shaped net is dragged along the ocean bottom; an otter door is attached to each side of the net to hold the net open and keep it horizontal. Fish collect in the cod end (the back) of the net. Source: Courtesy of Seafood Leader.

Figure 9. Towed or dragged fishing gear. Scallop dredging—a method of fishing which involves raking a metal frame with teeth and a chainmesh bag across the ocean bottom. Source: Courtesy of Seafood Leader.
Figure 10. Towed or dragged fishing gear. Trolling—a method of fishing in which several fishing lines with numerous lures are dragged slowing through the water.

Figure 11. Encircling gear. Purse seining—a method of fishing involving a long, deep net that stands like a fence in the water, supported at the surface by floats and held down by lead lines at the bottom. A person in a skiff takes one end of the net around the school of fish and joins it at the other end, and the vessel hauls in the wire purse line strung through the bottom of the net, forming a purse under the fish. Source: Courtesy of Seafood Leader.

Figure 11. Encircling gear. Purse seining—a method of fishing involving a long, deep net that stands like a fence in the water, supported at the surface by floats and held down by lead lines at the bottom. A person in a skiff takes one end of the net around the school of fish and joins it at the other end, and the vessel hauls in the wire purse line strung through the bottom of the net, forming a purse under the fish. Source: Courtesy of Seafood Leader.

costs involving machinery and equipment. All factors are combined to give the cost of a given harvest known as the catch per unit effort (CUE). However, the best CUE does not insure good quality in the fish landed, and a processor is somewhat at the mercy of the fishing operation for initial quality of raw materials from the sea.

The type of gear used in fishing has a definite bearing on the quality. When a fish dies after or during vigorous exercise, such as struggling on a hook and line, metabolic activity including that of protein and lipid degrading enzymes, adversely affects the subsequent spoilage rate of the dead animal. If a fish has been feeding and has food in its stomach, the increased metabolic activity greatly ac-

celerates the loss of quality in the slaughtered animal. The so-called soft belly of a fish is caused by this enzyme activity after the fish is dead. Because the amount of time that a hooked fish struggles is directly related to the subsequent spoilage rate, troll-caught fish are often of better quality than longline-caught fish that are allowed to die thrashing in the water.

The quality of gill net-caught fish is extremely variable depending on the length of time that the net is in the water. Hence, there can be a tremendous difference in the quality of fish taken from a given set, the last caught often being of higher quality. This factor is certainly realized by the wholesale buyers in that troll-caught fish consistently command a higher price than gill net-caught fish.

Certain visual or aesthetic factors also affect the market price of fish even though there may not be any real difference in the quality of the flesh. Marks from the web of a gill net are often caused when the fish struggles back and forth to release its entrapped gills. Unless the web causes cuts that allow bacteria to enter the flesh, these marks normally do not adversely affect the biological quality of the flesh. Hence, the word quality has different definitions, depending on whether it refers to the biological state of the edible portion or the visual appearance of the fish.

There are several types of fishing gear that cause abrasions and punctures during the catching and subsequent handling. Trawling, dredging, spearing or harpooning, and gillnetting all cause different degrees of damage. Trawling, which accounts for ca 40% of the world's fish catch, exerts extreme pressure on the fish as the cod end becomes full. In addition to scale abrasion, ruptures in the skin and internal portions release gut bacteria and decrease shelf life of the subsequent product.

The best quality is maintained in fish that are caught by trapping. As long as the trapping device is emptied on a reasonable cycle, the fish remains alive and is quickly killed prior to sale or processing. Some species, such as crabs, must be kept alive prior to butchering or there will be a blue color in the meat. This is due to the blood chemistry of crabs; they have a copper complex instead of the heme, or iron, complex found in most animals. If the crab is not butchered live and the blood removed prior to processing, the copper will oxidize, giving a blue color to the meat. Although the aesthetic value of the crab is impaired, the eating quality is not affected. However, as in the case of abraided fish skin, the consumer is not willing to consider blue crabmeat as anything but a low-grade, poor-quality product.

Aquaculture is somewhat akin to catching wild fish in trapping devices. The fish or shellfish are raised in an enclosed area and then removed when ready for market. As in the case of trap-caught fish, farmed fish are live when harvested.

Shipboard Handling of the Catch

The proper handling offish during harvesting and on shipboard can minimize the adverse effects of gear. Of utmost importance when fish are first landed is that they are segregated and placed in a sanitary chilled environment. Minimizing the bacterial and enzymatic activity by fast reduc tion of temperature in freshly landed finfish and shellfish is probably the most important step in the entire chain of events that takes a fish from the water to the table.

Figure 12 shows the extreme variation in storage life of fresh and frozen commercial fish prepared for the market. This curve has been compiled from many published sources that give the shelf life offish as related to the handling methods (6). It has been shown that landed high-quality fish that is chilled rapidly and carefully handled, processed, and packaged can be acceptable for up to three weeks after being caught. On the other end of the scale, a fish that has undergone poor handling on shipboard (eg, 70% of as caught quality) and subsequent marginal handling during the processing and marketing stages is inedible after four days.

Fish that has been properly handled, processed, packaged, and frozen can be held up to one year without significant deterioration. However, there are many factors that must be considered in discussing shelf life of a fresh or frozen product. The species, the oil content, the catching technique, and the state of the fish when harvested are all uncontrollable factors that have a major bearing on the shelf life of a seafood product.

PROCESSING SEAFOOD Inspecting As-Received Seafoods

Seafoods received in the processing area of a vessel or in a shore-based plant vary tremendously in the state and form. This is the situation when batches of product from different sources or catching vessels are mixed in the received lot. A sensory inspection must be made to insure that the raw material passes the criteria specified by the buyer or processor.

A sensory evaluation utilizes touch, odor, and sight to determine the acceptability of a given lot of seafood (7). An on-site inspection should concentrate on microbial contamination, enzymatic degradation, and other chemical and physical factors that reduce the marketability of the seafood. A faint fresh, nonfishy odor; firm and elastic flesh; bright and full translucent eyes; bright pink gills; and bright and moist skin surface with no heavy deposits of mucus or slime are all properties of a good fresh fish.

In addition to microbial and enzymatic degradation that can take place in improperly handled seafood, the oil in fatty fish that have not been chilled rapidly or adequately protected from the environment are subject to oxidative rancidity. This is both an aesthetic and nutritional problem. Oxidation from the air (and sometimes autooxidation within the seafood) not only affects the odor and taste acceptability of the product but also destroys the omega-3 (n - 3) fatty acids in the oil that are so important for human nutrition.

Preprocessing As-Received Seafoods

Preprocessing begins on shipboard where the seafood is, at the minimum, segregated and chilled. Many fish destined for the fresh market are butchered and washed. The minimal butchering operation consists of removing the visceral portion and often the gills. The ultimate in shipboard celerates the loss of quality in the slaughtered animal. The so-called soft belly of a fish is caused by this enzyme activity after the fish is dead. Because the amount of time that a hooked fish struggles is directly related to the subsequent spoilage rate, troll-caught fish are often of better quality than longline-caught fish that are allowed to die thrashing in the water.

The quality of gill net-caught fish is extremely variable depending on the length of time that the net is in the water. Hence, there can be a tremendous difference in the quality of fish taken from a given set, the last caught often being of higher quality. This factor is certainly realized by the wholesale buyers in that troll-caught fish consistently command a higher price than gill net-caught fish.

Certain visual or aesthetic factors also affect the market price of fish even though there may not be any real difference in the quality of the flesh. Marks from the web of a gill net are often caused when the fish struggles back and forth to release its entrapped gills. Unless the web causes cuts that allow bacteria to enter the flesh, these marks normally do not adversely affect the biological quality of the flesh. Hence, the word quality has different definitions, depending on whether it refers to the biological state of the edible portion or the visual appearance of the fish.

There are several types of fishing gear that cause abrasions and punctures during the catching and subsequent handling. Trawling, dredging, spearing or harpooning, and gillnetting all cause different degrees of damage. Trawling, which accounts for ca 40% of the world's fish catch, exerts extreme pressure on the fish as the cod end becomes full. In addition to scale abrasion, ruptures in the skin and internal portions release gut bacteria and decrease shelf life of the subsequent product.

The best quality is maintained in fish that are caught by trapping. As long as the trapping device is emptied on a reasonable cycle, the fish remains alive and is quickly killed prior to sale or processing. Some species, such as crabs, must be kept alive prior to butchering or there will be a blue color in the meat. This is due to the blood chemistry of crabs; they have a copper complex instead of the heme, or iron, complex found in most animals. If the crab is not butchered live and the blood removed prior to processing, the copper will oxidize, giving a blue color to the meat. Although the aesthetic value of the crab is impaired, the eating quality is not affected. However, as in the case of abraided fish skin, the consumer is not willing to consider blue crabmeat as anything but a low-grade, poor-quality product.

Aquaculture is somewhat akin to catching wild fish in trapping devices. The fish or shellfish are raised in an enclosed area and then removed when ready for market. As in the case of trap-caught fish, farmed fish are live when harvested.

Shipboard Handling of the Catch

The proper handling offish during harvesting and on shipboard can minimize the adverse effects of gear. Of utmost importance when fish are first landed is that they are segregated and placed in a sanitary chilled environment. Minimizing the bacterial and enzymatic activity by fast reduc tion of temperature in freshly landed finfish and shellfish is probably the most important step in the entire chain of events that takes a fish from the water to the table.

Figure 12 shows the extreme variation in storage life of fresh and frozen commercial fish prepared for the market. This curve has been compiled from many published sources that give the shelf life offish as related to the handling methods (6). It has been shown that landed high-quality fish that is chilled rapidly and carefully handled, processed, and packaged can be acceptable for up to three weeks after being caught. On the other end of the scale, a fish that has undergone poor handling on shipboard (eg, 70% of as caught quality) and subsequent marginal handling during the processing and marketing stages is inedible after four days.

Fish that has been properly handled, processed, packaged, and frozen can be held up to one year without significant deterioration. However, there are many factors that must be considered in discussing shelf life of a fresh or frozen product. The species, the oil content, the catching technique, and the state of the fish when harvested are all uncontrollable factors that have a major bearing on the shelf life of a seafood product.

PROCESSING SEAFOOD Inspecting As-Received Seafoods

Seafoods received in the processing area of a vessel or in a shore-based plant vary tremendously in the state and form. This is the situation when batches of product from different sources or catching vessels are mixed in the received lot. A sensory inspection must be made to insure that the raw material passes the criteria specified by the buyer or processor.

A sensory evaluation utilizes touch, odor, and sight to determine the acceptability of a given lot of seafood (7). An on-site inspection should concentrate on microbial contamination, enzymatic degradation, and other chemical and physical factors that reduce the marketability of the seafood. A faint fresh, nonfishy odor; firm and elastic flesh; bright and full translucent eyes; bright pink gills; and bright and moist skin surface with no heavy deposits of mucus or slime are all properties of a good fresh fish.

In addition to microbial and enzymatic degradation that can take place in improperly handled seafood, the oil in fatty fish that have not been chilled rapidly or adequately protected from the environment are subject to oxidative rancidity. This is both an aesthetic and nutritional problem. Oxidation from the air (and sometimes autooxidation within the seafood) not only affects the odor and taste acceptability of the product but also destroys the omega-3 (n - 3) fatty acids in the oil that are so important for human nutrition.

Preprocessing As-Received Seafoods

Preprocessing begins on shipboard where the seafood is, at the minimum, segregated and chilled. Many fish destined for the fresh market are butchered and washed. The minimal butchering operation consists of removing the visceral portion and often the gills. The ultimate in shipboard

Initial quality (time = 0)

Frozen quality

Initial quality (time = 0)

Frozen quality

6 8 10 12 14 18 20 v 2 3 4 5 6 7 8 9 10 Days Month

Storage time

Figure 12. Shelf life of fishery products. Source: Ref. 12.

butchering is heading and gutting, which consists of removing the viscera, head, and often the tail and fins. Shrimp are normally iced but sometimes the head is removed on shipboard. Crab are either delivered live directly to the shore plant or are kept alive in seawater tanks until delivery. In all shipboard preprocessing operations the most important procedure is to lower the temperature of the catch as soon as possible after it is taken from the water.

Preprocessing operations not carried out on shipboard are completed in the processing plant. After a second visual inspection, fish are butchered. This primarily consists of eviscerating but also can include scaling, trimming, and further cleaning when necessary for a specific processing operation.

Finfish are portioned for processing or direct marketing by filleting, steaking, or dressing a whole fish or section for roasting or broiling. Depending on the size and sophistication of the processing plant, these operations are carried out either by hand or machine. Crustacea (eg, crayfish, lobster, and crab) and mollusks (eg, clams, oysters, and mussels) are handled and processed quite differently from finfish.

Shrimp are iced on shipboard and unloaded by basket and conveyor into the plant receiving area. In the plant they are segregated and graded as to size by machine, passed over a visual inspection table for removing substandard specimens, cooked, and then headed and peeled (normally by machine). Large prawns are sometimes headed and handled individually on shipboard or in the plant. Those destined for market in an unpealed condition are then frozen. Prawns with head off and not cooked are called headed green prawns in the trade. Shrimp, regardless of whether they are marketed cooked and peeled, green fresh or frozen, or in other forms are sold by the count to designate size. For example 21-25 count shrimp means that there are 21-25 shrimp per lb.

Crab is cooked prior to processing or marketing. It is important that the crab are alive when butchered just before being cooked whole. This is due to the high copper content in the crab blood, which oxidizes to a blue color if allowed to remain in the meat of a dead crab. Crab, depending on the species, are sold in the shell whole (eg, blue and dungeness), segregated with shell on into legs and body portions (eg, king and snow), or as leg and body meat. Meat is removed or shaken from the cracked shell portions by hand.

Bivalves must be alive when purchased and subsequently cooked in a plant, restaurant, or home. A healthy live oyster, clam, or mussel will have a tightly closed shell. Any gapers, eg, those with an open shell, must be discarded. This requirement for handling only live molluscs is important because they normally are not iced after being harvested by digging, picking, dredging, or tonging, but are delivered directly to the receiving station or plant.

Problems involving toxins (eg, paralytic shellfish poisoning) or communicable diseases being transmitted to the consumer by mollusks have become increasingly more prevalent as the coastal waters become more polluted (8). These animals are static so they are particularly vulnerable to any fluctuating environmental pollution problem that may exist. Furthermore, the conditions causing the meat to be inedible cannot be detected by simple in-plant inspection. This has resulted in an intricate system involving surveillance of mollusk-growing areas by federal and local government agencies who are responsible for closing harvest areas when there is a potential problem.

Total Utilization

There is a growing emphasis on improving the total utilization of seafood raw material (8,9). For many years, only the most desirable portion of the fish, often accounting for 20 or 30% (eg, fillets) of the fish, was used. The remainder was considered waste or a raw material for preparing cheap animal feeds. Environmental and economic considerations dictate that this gross misuse of base raw material must be stopped. Hence, the modern attitude is that there is no such thing as fish waste. The portions remaining after the initial edible portion is removed should be considered secondary raw materials that can often equal or exceed the amount of the primary edible portion. The initial preprocessing operation must consider the ultimate total utilization destination of all portions of the raw material. Some of the products that can be prepared or manufactured from secondary raw materials are outlined in Table 7.

The developing operations and markets that use minced flesh for human consumption are beginning to have an impact on the economics of operating and the market for seafood products. Minced fish is used in engineered and formulated foods, the fastest growing segment of the food industry. Sources of minced flesh include

1. Frames (remaining skeleton) from a fillet operation.

2. Industrial fish presently being used for meal and oil.

Table 7. Total Utilization of Secondary Raw Materials from the Sea

Product

Table 7. Total Utilization of Secondary Raw Materials from the Sea

Product

Raw material

Edible

Industrial

Finfish"

Steaks

Meal, oil, pet foods,

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