Views: 210 Author: Wendy Publish Time: 2023-05-31 Origin: Site
Compared to meat and eggs, fish is a far more nutrient-dense diet, but it also spoils quickly due to its high moisture content (approximately 80%). Fish must be preserved as soon as possible after being caught to extend its shelf life. Fish can be transported and stored more easily and its nutritional value is preserved for a longer amount of time thanks to preservation techniques that also assist to keep it from spoiling and decomposing. Techniques for preserving fish differ depending on the kind, nature, size, and condition of the fish. When fish is handled and processed improperly, it immediately spoils and becomes of low quality. For fish preservation, traditional methods including chilling, freezing, drying, and chemical preservation are frequently used across the world. Among the different methods of preserving The earliest method of fish preservation is drying, which is the process of preserving fish by heating it to remove its water. Drying extends shelf life and reduces weight, volume, transportation, and storage space by removing moisture up to a particular point to stop microbial development. Natural drying and artificial drying are two frequently utilized drying techniques. Natural drying methods include the use of the sun and solar energy, while artificial drying methods include the use of microwaves, fluidized beds, spouted beds, infrared, connective drying, desiccant drying, freeze drying, osmosis, vacuum drying, pulsed electric fields, high hydrostatic pressure, superheated steam drying, heat pumps, and spray drying, among others.
The use of natural drying techniques has drawbacks such as contamination and damage from dirt, insects, rats, birds, and animals. Since sun drying of fish is slow and often takes five to seven days, the products are frequently of substandard quality. Therefore, in order to produce a high-quality product, a sophisticated drying technique must be used. Artificial drying techniques include benefits such faster drying times, more capacity, better process control, and better drying quality.
Drying involves the evaporation of moisture from the surface of the fish and the migration of moisture from inside the fish to the surface. Drying is affected by the movement of air over the surface of the fish as well as the temperature and humidity of that air. Sun drying of fish, with or without the addition of salt, is practiced in many tropical countries, and is a low cost form of preservation.
Vacuum drying is a process in which materials are dried in a reduced pressure environment, which lowers the temperature required for rapid drying. Major advantages of vacuum drying are as follows: less energy is needed for drying, it is highly suitable for heat sensitive food materials, faster method than other drying methods, it retains integrity of materials etc. In general, vacuum drying is performed in combination with other drying techniques.
Freeze drying or lyophilization is a dehydration process used to preserve a material and make it into more convenient for transport. It is a method of water removal from material by sublimation. This drying process is divided into three stages: pre-freezing of wet material, primary drying (sublimation of frozen water under vacuum) and secondary drying stage (desorption of residual found water from material). Freeze drying is initially freezing the material and then reducing the surrounding pressure to allow the frozen water in the material to sublimate directly from the solid phase to the gas phase. It is one of the best methods of water removal and results in a final product of much higher quality compared to any other drying technique.
A heat pump is a device that transports energy from a low temperature source to a higher temperature sink. This transfer requires an input of work which may be supplied mechanically as in a Vapour-compression cycle.
Dried fish processed through sun drying or dehydration is highly concentrated fish compared to other preserved form of fish.
As water content becomes reduced so microbial activity cannot run at normal rate thus reduce the spoilage of fish.
Less expensive method and comparatively simple procedure.
Reduced water content, enzymatic and many chemical processes 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.