The Journey of Sea Herring: From Ocean to Table

Sea herring, a versatile and widely utilized fish species, plays a significant role in both domestic and international markets. Larger herring are often exported, catering to a global demand for human consumption. Meanwhile, smaller herring are typically processed into canned sardines, a staple in many households.

The preparation of smaller herring for canning is meticulous. Initially, these fish are held in a purse seine for over 24 hours to ensure their stomachs are free from feed. This crucial step prevents enzyme reactions that could degrade the fish's quality. Once the herring are ready, they are loaded onto boats using a large vacuum pump and salted to begin the preservation process.

At the processing plant, the fish undergo further salting after being beheaded and eviscerated. Following this, they are reheated and placed in small rectangular cans. The herring are then steamed for 18-20 minutes to ensure proper cooking. After steaming, the liquid in the cans is drained and replaced with vegetable oil, tomato sauce, or mustard sauce, depending on the desired final product. The cans are sealed, heat-processed, and cooled, resulting in a shelf-stable product.

Larger herring are also canned, often whole, in larger oval cans with tomato sauce. Alternatively, they can be cut into bite-sized pieces and packed similarly. These products are designed to be shelf-stable, offering a convenient and long-lasting food source.

Beyond canning, herring are also pickled. This process involves using salt, vinegar, sugar, and spices, with additional ingredients like sour cream and onions sometimes added before sealing in glass jars. Pickled herring variants include rollmops (pickled herring strips wrapped around pickles or onions) and kippered herring (salted and lightly smoked). These products, however, require refrigeration to maintain their quality.

Another preservation method involves heavily salting and smoking herring, producing a shelf-stable product. Additionally, the scales from herring skins are collected in large quantities to manufacture pearl essence, a valuable by-product used in various industries.

In summary, sea herring's journey from ocean to table encompasses a range of processing techniques, each ensuring the fish's quality and longevity. Whether canned, pickled, or smoked, herring provides a versatile and essential food source, demonstrating its global significance and multifaceted utility.
The Journey of Sea Herring: From Ocean to Table

Fish canning process

The canning of fishery products may be divided into a number of definite steps applying equally well to all types, although details of methods and processes vary with the individual product.

Defrosting
If frozen fish are to be processed, they must first be defrosted. The thawing process involves the elevation of temperature of the fish to 0 °C, at which temperature it may be manually cut or otherwise prepared as necessary.

Butchering
The splitting and evisceration process is normally the only butchering operation

performed on the tuna while it is in the raw condition. This operation involves the scaling, evisceration, removal of parts not to be canned, and thorough washing in either salt or fresh water. The scaling may be done by hand with serrated-edge scrapers, the edges of knives or other means devised by the technician.

Salmon is traditionally filled into cans in the raw state. After grading, fish are fed into an iron chink butchering machine for the automatic removal of head, fins and viscera.

Pre-cooking
Sardines, mackerels and tuna are normally pre-cooked prior to sterilization. The object of pre-cooking, particularly in the case of tuna, is to facilitate the removal of flesh from the carcass.

Typically, sardines are packed into quarter club cans, which are placed in square plastic trays. The trays may hold some 4 x 7 cans each. A thin sheet of metal is placed over the tray and the whole inverted and placed on racks on a trolley which is then wheeled into a batch pre-cooker.

Functions of pre-cooking:
• Firm texture of fish
• Reduction in bacterial load
• Inhibition of enzymatic reaction
• Shrinkage for better filling
• Removal of cellular gases

The time for pre-cooking in steam at a temperature of 105 °C is about 30 minutes depending on the size of the fish.

Can filling
Before being canned, the cans and jars are rinsed with water under pressure of steam before being filled.

Filling may be accomplished either by hand or by machine. Can filling in large tuna factories is undertaken by high-speed machinery. The tuna is formed into a tube within the machine and sliced to the correct height and fill weight on presentation to the can. Smaller fish and meat scraps are generally canned as flakes after being pressed into moulds.

Sardines are traditionally filled manually into cans prior to pre-cooking, but automatic machines are also available.

Mackerel are processed in both rectangular and cylindrical cans and the filling operation may take place manually or by suitable machinery according to the size of the operation.

Covering liquid, oil, brine or sauce is added to fish within shallow cans to overflowing. The excess liquid is screened and returned to the filling head.

Fish and the liquid added to the can should be packed tightly to prevent it from shaking around and braking up into undesirable looking pieces, requires the fish to be packed in an orderly fashion.

The weight is checked at this point to prevent excessive filling that could lead to the foodstuff not being processed appropriately, swelling of the tin or even bursting of the seams.

The can may then be closed using steam flow to remove air and provide a vacuum within the can. Then the can is sealed. The sealed cans are cleaned to eliminate any remarks of filter and they are prepared for sterilization.

Heat Processing
Fish products and other low-acid foods are usually processed in steam at temperatures of 115° to 120°F. This operation is usually carried out in heavy metal airtight receptacles (retort) that will stand internal pressures of 20 and 30 pounds or more to the square inch.

Can coding
Coding may be applied to the ends of cans by use of embossing machines, or more frequently nowadays, by the use of ink jet machines.
Fish canning process

Fish sausage

Sausage is a product widely consumed worldwide and contains basically meat and fat (solid phase) dispersed into ice/water (liquid phase) forming a stable mass that will be submitted to a moderate heat treatment.

Fish sausage is one of the nutritious, whole-some, palatable, flavoursome, and low priced. The addition of fish meat in sausage formulation could improve nutritional quality of the product and can be a way to insert fish meat in human diet.

Conventionally, fish sausage is prepared by mincing and grinding fish meat (70%) with other ingredients such as starch (9% ), sugar (1.5%), salt (2.5%), vegetable fat (5%), spices (1%), preservatives (1.1%), colouring substances (0.13%), and stuffing the paste into casings and processing it at 90°C for 1 h.

The raw materials for fish sausage are not necessarily certain particular species of fish. Fish sausage can be made of fish flesh that has little elasticity. Many kinds of fishes are now used as raw materials for fish sausage, for example, tuna, marlin, skipjack and bonito, salmon, and whale.

The overall quality of fish sausage includes acceptability of mechanical properties and appearance. Appearance is affected by the extent of packaging, color additives, and sensory properties, which are determined by flavor and texture in the emulsion sausage.

Textural properties are changed by biochemical degradation due to the storage time and farinaceous filler content, which often leads to softening over time. Texture is a vital sensory characteristic that determines the quality and acceptability of a fishery product.

Fish is known as a rich source of long-chain n-3 fatty acids, and those fatty acids are known to have a range of health benefits. Especially potential roles in reducing the risk of coronary heart disease, inflammatory disorders, and immune disorders have resulted in interest among consumers and manufacturers.
Fish sausage

Canning of fish

Canning is a method of storing food in airtight containers in a way that destroys potentially harmful microorganisms such as bacteria.

Most canned fish products are composed of ingredients that result in finished product with pH above 4.6 and water activity greater than 0.85.

These characteristics result in canned fish products being considered ‘low-acid canned food’. Canned fish have a shelf life of one year while frozen, oily fish should be used within two months.

Canned fish is conventionally covered with a liquid such as brine, vegetables oil tomato sauce or other sauces.

The canning process depends on the size of the fish. Small fish species such as sardines and pilchards are generally canned whole, with only the heads and tails removed. These whole-fish products are cooked in the can after it has been filled with brine or oil.

Canned fish is that it’s already cooked and ready for many easy dishes such as fish cakes, quiche, loaf, salads, sandwiches and appetizers.
Canning of fish

Tuna fish canning

At the processing plant, the fish are thawed in holding rooms at ambient temperature or in tanks with running water.

When thawed, the fish are eviscerated and washed. They are then cooked in steam, under pressure, and then cooled.

Precooking removes most of the strong flavored oils. The strong flavor of dark tuna flesh affects the delicate flavor of white flesh. When cooled, the heads and skins are removed.

The fish then cut longitudinally after which all bones and the dark meat are removed.

The white meat is shaped, mechanically into a cylinder, feed into cans and cut to length. To pack chunk style tuna, pieces are filled into cans with adjustable filler.

Vegetable oil or a broth containing hydrolyzed vegetable protein in water is metered into the cans, are then heated in steam, sealed, heat-processed. The sterilized cans are cooled in ruining water, wiped and kept in a cool place 10-15.5 °C. The cans then are labeled and stored.
Tuna fish canning

Frozen tuna aboard the boat

Most tuna fish fishing boats make trips lasting for several months and for this reason, the fish are usually frozen aboard the boat.

The freezing process depends on the type of tuna. For bluefin tuna as an example, fisherman first cut the tail and gills, then gut bled and freeze it t -65 C for 35horus before placing them in to the fish hold at -60 C.

Normally in freezing, the whole fish are cooled in large well with refrigerated sweater circulated through it at 28 F (-2.2 C). Once the fish are cook led, the refrigerated seawater is pumped out of the well, and it is replaced with refrigerated bone at 10 F (-12.2 C) or lower.

When the fish are frozen, the brine is pump out of the well, and the fish are kept frozen in the dry well by circulating mechanically refrigerated air.

In one system brine is sprayed on refrigerated pipe coils located in the hold of the vessels until a coating of ice one foot thick or more is frozen. The compartment is then filled with fish and is flooded with brine. Accumulated ice provides refrigeration capacity needed to chill the brine and freeze the fish.

They remain there until the boat arrives at port.
Frozen tuna aboard the boat

Canning of fish

Fish used for canning include sardine, anchovy, pilchard, tuna and mackerel.

The fish is received and unloaded in the plant by electric winches, washed, put in brine and transported to the heading, gutting and cutting machines.

Fish for canning must be of highest quality. In comparison with most animal products, fish spoil much more rapidly, and pelagic fish tend to be more susceptible than other species.

Small sized fish species are canned whole, whereas medium seized species are first nobbed and then cut into pieces before canning.  The can are weighted, the tops sealed and placed in a retort for cooking.

The number of stages, or their order within the canning process, can vary according to whether large or small species are being used, whether continuous or batch processes have been chosen, whether manual or mechanical labor is being utilized.
Canning of fish

Processing of Cod

Processing of Cod
At the processing pant, the cod are washed and filleted, skinless.

Fillets that are to be frozen for the retail trade are packed in 1 lb (454 kg) waxed carton with or without being first wrapped in moisture vapor-proof plastic.

The fillets may have been passed through a weak brine (10 – 45% saturated salt solution) prior to packaging. For purposes of freezing, retail sized cartons of fillets may be placed on trays, the trays placed on racks, and the racks wheeled on top a blast freezer where very cold air is blown over the product, or the cartons may be plate frozen by being placed in trays in contact with refrigerated plates at -28 degree F (- 33.3 degree C).

Some cod fillets are frozen, usually in a plate freezer, and then cut into fish sticks or fish portions that are then breaded in a batter of flour, dried milk solids, egg solids, spices, and flavoring.

The product is then packaged in retail-sized units and held frozen until sold to customers.

Salted cod was once a major export commodity of the United States, only very little cod is now salted in this country. To produce salted cod, the fish are beheaded and split longitudinally; the backbone and the abdominal cavity lining are remove, washed and layer salted in closed casks (brine salting), in open tubs, or simply in open piles on a low platform (dry salting).

Most of the salted cod is produced by dry salting that is done to produce either a lightly salted product or a heavily salted product. The lightly salted product requires many days to complete, has a relatively low salt content (less than 10%), has better organoleptic properties than the heavily salted once, but it is not shelf stable, the heavily salted product requires week to complete, has a high salt content (about 30%) and is shelf stable.
Processing of Cod

The Soft-Clam Shell

The Soft-Clam Shell
The soft-clam shell is found in the Western Atlantic as far as the Artic regions and as far south as Virginia, being most plentiful off the coasts of New England, New Jersey and Virginia.

In New England, soft-shell clams are harvested when the tide is low by digging into the mud with the short handled clam hoe and removing them by hand.

In the Chesapeake Bay area clams are harvested from boats using water jet dredges and escalator. They are placed in bags or basket and brought to the processing plant, where they are washed with sea water and sorted according to the size.

Specimen 3 in. (7.6 cm) in length or less are usually cooked by steaming. The larger size clams are removed from the shell by hand and placed in metal containers, after which the containers are refrigerated by being surrounding with crushed ice.

In this form, they are shipped to restaurants to be served as a breaded deep fat fried product. Soft-shell clams may be removed from restricted areas and depurated.
The Soft-Clam Shell

Processing of Hard Shell Clam

Processing of Hard Shell Clam
In preparing hard shell clam for the market, they are washed with sea water graded for size, and cooled. Some clams may be taken from semi polluted waters provided they are depurated.

In the shell, hard shell clams are marketed according to size. The different sizes are “chowders” (large size), which are used to prepare chowders, fritters, or stuffed clams; “cherrystones” (medium size), which are used for baking; and:”little necks” (small size), which are used as steamed clams or for eating raw on the half shell. Hard shell clams are neither canned nor frozen in significant quantities.

Hard Shell clams may be cultured. In such instances, the bottom is first prepared by removing thick grass, stones and other debris. Predators, such as starfish, cockles, conchs and welks, are removed by raking and by towing floor mops over the bottom (to entangle starfish). The young clams, raised in tanks, are then spread over the area by scattering them from the side of the boat, using a shovel. Once seeded, the area is left undisturbed to permit the clams to grow to harvesting size. Predators may be removed from times to time. After seeding, the area may seed itself naturally.
Processing of Hard Shell Clam

Oysters Processing

Oysters Processing
Oysters are harvested with rakes, tongs, dredges, or with water jet vacuum dredges. Oysters and other bivalves, except scallops, are able to live out of water at suitable temperatures for some times. Since they can obtain oxygen from that which is dissolved in the water retained within the shell in contact with the gills. Aboard boats, oysters and clams must be held under sanitary conditions away from the bilges. The boat used to harvest bivalves should be outfitted with a chemical toilet so that growing areas will not be polluted with the human discharges.

At the processing plant, oysters to be marketed in the shell are washed in seawater which may be chlorinated, packed in sacks or barrel, cooled and shipped to restaurants. They should be held at temperatures between 32 degree F and 40 degree F. Most oysters are shucked by hand with the aid of a knife. The meats are washed or agitated in fresh potable water by air blown into the wash tank, graded for size, and packed in glass or metal containers. The filled containers are cooled and shipped to market in crushed ice.

Oysters are eaten raw from the half shell or in stews (lightly heated in milk with some butter) or breaded and deep-fat fried.
Oysters Processing

Sea Herring Processing

Sea Herring Processing
The larger fish may be used for export, as there is a foreign market for this species where it is used for human food. The smaller herring, which are canned sardines, must be held in the purse seine (sometimes for longer than 24hrs) until the stomach is free from feed. This is done to prevent enzyme reaction, which would reduce the quality of the fish. Fish from nets are loaded on the boat with a large vacuum pump and are salted. More salt is added at the processing plant after the fish beheaded and eviscerated. The small herring are then reheated, placed in small rectangular cans, and subjected to steam for 18-20 min. The liquid in the cans is drained and replaced with vegetable oil. Tomato sauce, or mustard sauce; and the cans are sealed, heat processed, and cooled. The product is shelf-stable.

The larger herring are also canned whole but in larger oval cans, usually in tomato sauce. Some large herring are cut transversely into bite size pieces and packed in small cans in tomato sauces. This product is also shelf-stable.

Some herring are pickled (salt, vinegar, sugar, and spices) and packed in glass jars. Sour cream, onions, or other flavoring ingredients may be added before sealing the jars. Other pickled products include rollmops (pickled herring strips wrapped around a piece of pickle or onion) and kippered herring (salted and lightly smoked). These products must be refrigerated. Some herring are highly salted and heavily smoked, and this product is shelf stable. Large quantities of scales from the skins of herrings are recovered and used for the manufacture of pearl essence.

Sea Herring Processing