Preservation of Fish

Preservation of Fish

	Preservation of Fish - The microflora of living fish depends on the microbial contents of the water in which the fish live. Fish microflora includes bacteria such as species of Pseudomonas, Alcaligenes, Vibrio, Serratia, Micrococcus etc. The level of contamination can increase with the type of processing and subsequent handling. Fish is also susceptible to autolysis, oxidation and lipolysis in addition to microbial spoilage. Its preservation, therefore, should involve a combination of treatments. Avisceration should be done immediately to prevent the gut enzymes from becoming functional.
Preservation of fish by chilling temperatures is only a temporary method and freezing is the best way to preserve fish for a longer time. Freezing kills most organisms but not the psychrophiles and the spores. Most of these survive freezing and grow during thawing. Fish preservation by radiation bas been tried and found successful specially when used in combination with freezing. Salting and drying method of fish preservation is an age old custom. Sodium chloride serves both as a chemical preservative as well as binds the moisture. This may, however, not affect the halophiles which sometime cause discolouration during drying. Other chemicals used in fish preservation to retard microbial activity include sodium and potassium nitrite and nitrate, benzoate and sorbate.
A dip in antibiotic solutions has been tried and found' successful but these days it is not encouraged.The kind and rate of fish spoilage varies with a number of factors, such as the kind of fish, the condition of the fish, the level of contamination, the storage temperature and other pretreatments. Bacteria causing spoilage of fish are a part of the natural flora and the predominant bacteria causing spoilage are species of Pseudomonas, Achromobacter, Flavobactrium, Micrococcus and Bacillus. Some of these bacteria can grow at low temperature, first on the surface and later penetrate into the flesh.It has been found that flat or fatty fishes deteriorate rapidly than round fish. Fish that has been excessively handled undergoes quicker spoilage.

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