Metodos Tecnicas Conservacion Pescado

Preservation Techniques

Many different techniques have been used to preserve fish quality and to increase their shelf life. They are designed to inhibit or reduce the metabolic changes that lead to fish spoilage by controlling specific parameters of the fish and/or its environment. These techniques can be classified as follows:
Techniques based on temperature control
These encompass a widearray of technologies used to decrease the fish temperature to levels where metabolic activities - catalyzed by autolytic or microbial enzymes - are reduced or completely stopped. This is possible by refrigeration or freezing where the fish temperature is reduced, respectively, to approximately 0 °C or < - 18°C.
Fish refrigeration can use cool air circulating around the fish (mechanicalrefrigeration) or icing. Fish icing and boxing on-board fishing vessels is not always possible in the case of small pelagics that are caught in large quantities. These are chilled using refrigerated seawater (RSW) or chilled seawater (CSW). Chilled or frozen fish products require additional cooling in cold store to avoid an increase in temperature.
The design (size, insulation, palletization) andmanagement of cold stores are key for fish quality and energy saving. A major environmental issue relates to the development of alternative refrigerants to replace the chlorofluorocarbons (CFCs) which are damaging to ozone layers.
Techniques based on the control of water activity
Water activity (aw) is a parameter that measures the availability of water in fish flesh. It is expressed as the ratioof water vapour pressure in fish/vapour pressure of pure water at the same temperature and pressure. Aw varies from 0 to 1.
Water is necessary for microbial and enzymatic reactions and several preservation techniques have been developed to tie up this water (or remove it) and thus reduce the aw. These include drying, salting, smoking, freeze-drying, the use of water binding humectants and acombination of these. Some of these techniques, such as drying, salting and hot smoking, have been used for thousands of years. They can be implemented very simply, e.g. by salting, solar drying, or using fully automated equipment with temperature control, relative humidity, etc.
Techniques based on the physical control of microbial fish loads, its chemical and enzymatic activity
These physicalmethods use heat (cooking, blanching, pasteurizing, sterilizing), ionizing irradiation (for pasteurization or sterilization) or microwave heating. Cooking or pasteurizing are processes that do not allow complete inactivation of microorganisms and thus often need to be combined with refrigeration to preserve fish products and increase their shelf life. This is not the case of sterilised products andwhich are stable at ambient temperatures (< 40°C). These require packaging in metal cans or retortable pouches before the heat treatment, thus the term "canning".
Techniques based on the chemical control of microbial activity and loads
These techniques are designed to add anti-microbial agents or decrease the fish muscle pH to levels that are inhibitory to microbial growth andproliferation. Most bacteria stop multiplying at pH < 4.5. The decrease of pH is obtained by fermentation, marinades or by adding acids (acetic, citric, lactic, etc.) to fish products.
In addition to the decrease in fish pH, fish fermenting lactic bacteria also produce anti-microbial compounds such as nisin, which improve preservation. This technique is often referred to as bio-preservation. Otherpreservatives include nitrites, sulphites, sorbates, benzoates or natural ones such as essential oils.
Techniques based on the control of the oxydo-reduction potential
Some spoilage bacteria and lipid oxidation require oxygen. Reducing the oxygen around fish will increase its shelf life. This is possible by vacuum packaging or by controlling or modifying the atmosphere around the fish. Specific...