Sorting of dried fish

Fish is an extremely perishable food item and required preservation for future uses. Several preservation methods are followed over the world for preserving fish. Aim of all these methods is same- to extend the shelf-life of fish so that the fish can be used in future properly. One of these methods is "drying” which is the oldest known method of preserving perishable food items including fish. In Bangladesh, sun drying is the most widely used method of fish preservation. This method is also considered as the least expensive method of preservation.

Generally two terms are now being commonly used in drying of fish viz. "sun drying” and "dehydration”. These two are both the methods of preserving fish, almost similar but with little differences. Drying involves removal of water content from the fish body. In Sun drying this process is carried out by exposing target fish directly under the sun. This is usually done in the open air using solar energy to evaporate the water content in the fish. Natural air carried away the evaporated water from fish body.

Dehydration, almost same as sun drying, except that this process is practiced under controlled operational parameters like air temperature, relative humidity, air velocity etc. Common practice is to dry fish in an enclosure provided with facilities to control these parameters.

Household fish drying

Drying of Silver carp

Advantages of dried fish:

• Dried fish processed through sun drying or dehydration is highly concentrated fish compared to other preserved form of fish.
• As water content become reduced so microbial activity can not run at normal rate thus reduce the spoilage of fish.
• Less expensive method and comparatively simple procedure.
• Reduced water content, enzymatic and many chemical process which are responsible for fish spoilage retarded.
• In this method, complicated machinery and equipment are not required.
• Dried fish remain stable at most ambient temperature.

Disadvantages of sun drying:

Though drying has some positive sides, but it has some disadvantages too. The major problem of sun drying is efficiency and quality of final product remain at the mercy of nature (i.e. operational parameters). In improper sun drying, dried product suffers from many disadvantages. Some of these problems are-

• This process is can only be carried out when bright sunlight is available. Also no control over the operational parameters.
• Long duration required. Sometimes under unfavorable operational parameters it takes several days to complete which affects the quality of final product.
• In sun drying, possibility of contamination with dust, sand; infestation with insects, their eggs and larvae is high.
• Shelf life of the final product is not too long and poor quality final product is produced in most cases.

In Bangladesh, some other problems are very conspicuous which are as follows-

• Low or poor quality raw materials (fish) are used.
• Inadequate washing and dressing of raw materials.
• Place of dressing, drying is not hygienic and also people associated with this process used unclean intensives.
• Use of insecticides at a high rate to avoid insect infestation which damage the quality of the product and this is very harmful for human health.

Advantages of Dehydration over Sun drying:
In dehydration process, as drying is carried out under controlled environment, most of the disadvantages faced in "sun drying” can be overcome and desired quality of final product can be maintained. Dehydrated product have comparatively long shelf-life than sun dried product.

Drying of Boal (Wallago attu)

Driers:
Driers are devices used to dry fish under controlled environment. A variety of driers are used for drying fish, e.g. Cabinet drier, Kiln drier, Tunnel drier, Spray drier, Solar tent drier etc.

As huge amount of fish is caught is made during season and other time of the year in the country, it is so hard to consume all the catch fresh. So preservation is essential for extra catches. Considering the economic and other conditions of dry fish farmers and existing facilities and weather of the country Bangladesh, sun drying of fish is considered best way to preserve fish. But dry fish farmers need financial support and training on basic knowledge of scientific drying process. Government and associated organizations should take proper steps to train them all with financial support and also introduction of monitoring them and proper monitoring of quality maintenances is required.

Tent for storing dried fish