Preservation and also can cause the loss of water

Preservation Techniques There are many preservation techniques widely used such as chilling, freezing, drying, curing, conserving, vacuum packing, modified atmosphere packing, acidifying, fermenting and adding preservations. A smaller number of techniques act by inactivating microorganisms e.g.: pasteurization, sterilization and radiation. Addition techniques such as processing and packaging prevent access of microorganisms to products. There are new and emerging preservation techniques which are under development or have recently been brought into use examples of new and improving techniques are, ultrahigh pressure, electro poration and the addition of bacterolytic enzymes.  Among the traditional processes are smoking, salting, drying and marinating. It is highly stressed that the quality of fish products will be influenced by each action during processing and preparation. It’s important to adapt the process to the special requirements that help prevent the spoilage of fish and fish products. If processing techniques are applied in the correct way products of high quality and nutritional value will be achieved.  Heating of fish products during cooking, canning or smoking, can disturb the cell membranes and aid lipid oxidation (Gray and Pearson,1870), which effects the nutritional value of the fish/ fish product. However, the addition of antioxidants during processing can reduce negative effects such as these. Quality of the final products is significantly influenced by the quality and the freshness of the raw product. Nowadays most fish are transported in a frozen state. The quality of the final product is influenced mainly on the freezing, thawing and storage times of the seafood. It’s very important to freeze the fish as quickly as possible after harvest. When freezing the fish, the fish should be frozen to –30 0C before transferring to storage (Fish processing technology- second edition). It’s very important to have a fast freezing process to avoid the formation of large ice crystals that may cause the destruction of cell membranes which leads to the risk of oxidation, damage to the texture of the fish and also can cause the loss of water holding capacity (Alizadeh, Chapeau, de Lamballerie, & Le-Bail, 2007). As the temperature drops, more water is converted to ice and the concentration of enzymes in solution is increased, therefore the freezing point of water, this indicated that temperature and freezing points are closely related. It’s very important to maintain a stable temperature in order to avoid the growth of crystals (Li & Sun, 2002). Thawing must have similar precautions similar to the importance of the precautions taken for freezing. (Li & Sun, 2002) present some modern thawing methods and their advantages to increase flesh quality and to help reduce thawing losses. Curing drying, salting and smoking Curing as a means of preservation has been used traditionally and perhaps has been practiced longer than any other form of preservation. Curing is known to be a flavoring process and preservation technique for foods, by the addition of salts, sugars, nitrates and the aim of curing is to achieve a reduction in the moisture of the food by a process known as osmosis. Osmosis is the movement of a solution from an area of high concentration to an area of low concentration, through a semi-permeable membrane. Salting, smoking and drying are techniques which have been used in the past for many generations and from the beginning has not been altered a lot since prehistory. Modern developments in these preservation methods are based around the areas of what causes the food product to spoil and to achieve a standardized product which is demanded by the consumers (Fish processing Technology written by George M Hall, second edition). Quality of the final product is influenced by many factors such as many salting techniques; ripening and drying time and their conditions and also the salt composition. In generally the salt which is used in this process is sea salt, as it is widely available and thus practical. Salt which has high proportions of calcium and magnesium ions which improves the texture (Lauritzen, Akse, Gunderse, & Olsen, 2004). Before consumption of the fish after salting the fish must be soaked in water for 24 hours and washed to ensure the desalting of the product.  The absorption of salt into the fish muscle depends on many factors such as the fish species, size, weight, fillet thickness and the composition, it is also based on the length of time the fish is salting for, the concentration of the salt and the salting procedure which has been carried out (Gallart-Jornet et al., 2004), (Fish processing Technology by George M Hall, second edition).  Drying of the fish as a process of preserving the seafood is one of the oldest traditions used, and dried fish have a storage life for several years. Traditionally the best form of drying was to let the wind and the sun dry it. As mentioned previously fresh fish have short storage life’s unless preserved correctly, with drying it removes water from the seafood, which inhibits the growth of microorganisms.