I. Preservation Process and Further Process of Fish

Fish processing is the fish and fish products processes involved between the time fish are caught or harvested, and the time the final product is delivered to customers. And the preservation process that is to retain quality increase the shelf life of fishes, and the further process for value-adding to produce a wide range of fish products can be involved in fish processing.

1. Fish preservation process

Fish is a kind of perishable food, so the first and most obvious handling should be preserving the quality of fish to keep them alive for as long as possible before cooking and consumption.
And a number of methods and techniques are developed and used for fish preservation. Among the preservation methods, some are completed based on temperature control, using ice, refrigeration or freezing; others are completed on the control of water activity, including drying, salting, smoking and freeze-drying. Techniques may rely on the chemical control of microbial activity and loads by adding acids, for example, to fish products; or rely on the physical control of using heat to kill the bacteria that causes decomposition, and the heat can be produced by cooking, blanching or microwave heating in a manner that realizes pasteurizing and sterilizing fish and fish products; techniques are also used that are based on oxydo-reduction, such as vacuum packing. Most often a combination of different techniques is used to preserve fishes.

1). Drying fish

Drying fish is to reduce the moisture of fish to a proper degree to realize preservation. Sun-drying is using the heat of the sun and movement of air to remove the moisture of fish, and this is a traditional way which is still in use today. Sun-drying does not allow much control over drying time. The moisture percentage will depend on the oiliness of the fish and whether it has been salted.

2). Salting fish

A concentration of 6-10% salt can prevent the bacteria activity in the fish flesh because most bacteria in food cannot live in salty condition. The fish preserved by salting has a longer shelf life. However, a group of halophilic bacteria is salt-loving and their activity cannot be controlled even at a concentration of 6-10%. So, some further processing of removing water by drying is necessary to inhibit these bacteria.
Salting needs minimal machines or equipment, but how salting is applied is important. The traditional method is rubbing salt into the flesh of the fish or making alternate layers of fish and salt. To improve the situation of fish preserving insufficiency caused by not using salt uniformly, a better technique of brining is utilized. Brining involves immersing the fish into a pre-prepared solution with a concentration of 36% salt, and its advantage is that the salt concentration can be more easily controlled and salt penetration is more uniform. Brining is usually applied combining with drying.

3). Smoking Fish

Smoke produced by burning wood contains a number of compounds which inhibit bacteria. Heat from the fire causes drying, and if the temperature is high enough, the flesh becomes cooked. Both of these factors prevent bacteria growth and enzyme activity which may cause spoilage.
Smoking is not only done as a preservative but also done for the unique taste and flavor imparted by the smoking process in recent times. Smoking has two types of methods: cold smoking, of which the temperature is not high enough to cook the fish; and hot smoking, of which the temperature is high enough make the fish cooked.

2. Further process of fish

The further process includes processing fish into a wide array of value-added products, which is more important nowadays due to societal changes that have led to the development of outdoors catering, convenience products ready to eat or requiring not much preparation before serving; as well as proper waste management after intensive processing.
Further processing of fish can make the fish products have different flavors and textures, increase their economic value, and allow the fishing industry and exporting countries to get the full benefits of their fish resources. At the same time, further processes with value-adding generate further employment and hard currency earnings.

II. Final Products after Fish Processing

Fish processing can be subdivided into fish handling, which is the preliminary processing of raw fish, and the manufacture of fish products.

1. Fish products for preservation

As mentioned above about fish preservation, this kind of fish products is dried fish, salted fish, and smoked fish.
—Products of raw fish
1). Drawn fish: a whole fish has its internal organ removed
2). Dressed fish: fish that has been scaled and eviscerated, and ready for the cook
3). Pan-dressed fish: a dressed fish with no head, tail and fins to fit in a pan
4). Filleted fish: boneless fish flesh that is cut lengthwise from the fish along the backbone; it is popular in western countries for its little preparation for cooking
5). fish steaks: large dressed fish can be cut into cross-section slices, usually half to one inch thick, and usually with a cross-section of the backbone
6). Fish sticks: pieces of fish cut from frozen fish fillet blocks into portions of 3/8-inch thick
7). Fish cakes: packed or frozen cake-shaped product that is prepared from flaked fish, potatoes and seasonings
—Products with value addition:
Surimi and surimi-based products are prepared from the mechanically deboned, washed and stabilized fish flesh, and they are an intermediate product used in the preparation for some ready-to-eat seafood.
Fish meal is a product made from fish, and bones and offal of processed fish. It is a kind of brown powder or cake obtained by drying the fish or fish trimmings. If the fish is fatty, it can be pressed to get fish oil.

III. Mechanical Fish Processing Machines and Equipment

1. Fish Refrigeration Equipment for Transport

For supplying the distant market, fish and fish products are chilled and frozen and then transported by road, rail, sea or air. So it is essential that the cold chain is kept operating throughout, which requires the utilization of transport vehicles or insulated containers with adequate quantities of coolants or mechanical refrigeration. Container technology has made it possible to combine refrigeration with a modified or controlled atmosphere.
—Processing Machines for Fish Products
The need for higher productivity and the increase in labor cost have driven the development of automatic scaling, skinning and filleting machines, etc.
1). Fish grading machine: it can finish sorting fish by sizes. Grading by species has to be done the manual operation.
2). Automatic fish scaling machine: fish scale has to be removed before serving, it is the work that the fish descaling machine does.
3). Fish cleaning machine: this facility is able to have a full cleaning of fish by fish back dissecting, fish guts removing, membrane cleaning, etc.
4). Fish cutting machine: to meet the different processing requirements, usually fish needs to be cut into different shapes of fillets, slices, segments, strips, blocks. etc., and the fish cutting machine can help this.
5). Fish flesh separator machine: it can achieve collecting fish flesh from fish bones, which is a requisite management for the fish ball, fish noodle, fish gelatin, etc.
6). Fish drying machine: with demands for the improvement in the quality of dried fish, there has been a great deal of research on the development of the advanced drying machine with mechanical function. Microwave meat drying machine and hot-air drying oven are the two kinds of mechanical dehydrating equipment used in industrial fish processing.
7). Fish brine injector: this machine works by injecting saline and seasonings into fish flesh evenly and continuously to complete fish salting and pickling.
8). Fish smoking machine: Due to the aquaculture production increase as well as the request for high-quality products of people, the need for developing modern fish smoking machinery and techniques is necessary. The automatic fish smoking machine has replaced the traditional smoking machine and technology by employing an improved smoking method to process fish in a more health and sanitary way than the traditional smoking method.

IV. Fish Waste Management

There will be a lot of fish waste after processing, such as fish head, fish skin, fish scale, fish tail, fish bone and residual fish meat, which account for 40-50% of raw fish weight. These fish waste are rich in protein, fat, minerals, and to avoid waste of resource, they have been developed to use in the fields of the chemical engineer, food, biology, medicine, environment protection, etc.