Method of Fish Preservation

Firstly, we already know that, fish is highly perishable commodity, which spoiled very rapidly due to the infection of the various types of micro-organism.

            So, for this, we have to manage strong and peculiar method fish preservation, so that its frequency of spoiling can be greatly decreases. For the prevention of fish spoilage, there are many types of process in which some are very popular methods of preservation like, drying, canning, icing, etc. All this process are categorized under physical and chemical method of fish preservation and they are as following,

Type of preservation:- 

1)      Physical method

2)      Chemical method

Chemical methods of preservation is nothing but the preservation of fish like commodity by the application of different types of chemical substance, which we are using from earlier day of preservation like, benzoic acid and sodium benzoate etc.

Similarly physical method of preservation is also very common and some of them are very much popular to fisherman and their crew member.

Physical methods of preservation:-

1)      Drying and dehydration

2)      Canning

3)      Freezing / icing

4)      Salt curing

5)      Smoking  / smoke curing

6)      Marinades

These are some of the method of physically preservation of fish.

1)      Drying and dehydration:-

It is the method of fish preservation in which the moisture content of fish is removed by drying and then process called dehydration. As we know that, for any microbial reaction their must a wet / moist medium to flourish them. So they cannot perform these types of activity after dehydration process. By this action of dehydration almost 90-95% of moisture is removed from the fish. Then they are packed in the specific packaging material.

2)      Canning:-

It is very popular type of physical preservation in which selected food material are prepared for the consumer table, packed in tin or glass container capable of being sealed air tight, heated sufficiently to destroy the spoilage organism within the container and cooled rapidly. It is similar to the drying, but in it food is heated in a sealed and air tight metal chamber to destroy the micro-organism and rapidly cool down.

Unlike other method of preservation canning alter the nature of material significantly forming almost new products because of various treatment, the raw material are subjected to and various additives used in processing. Containers for canned foods are normally made of tinplate, but aluminum and other modification are now a day’s popular.

3)      Icing / Freezing:-

It is a method of food preservation employing low temperature, icing and chilling can maintain fish fresh only for a very limited period. Quality deterioration takes place in chilled fish. Freezing is a method low temperature preservation of fish that can ensure very long shelf life and can also provide a processed product very much similar to fresh fish. Most methods of long term preservation bring about major changes in the physical, chemical, textural and organoleptic characteristic of fish.

Main principle behind this method is cool temperature do not favors the all activities of microorganism and also its enzymatic activity becomes inactivates, due to low temperature. Icing is done in 1:1 ratio, means one layer ice and one layer fish and so on. So that it does not make contact in other fish and also the weight should not be increased so much to lower side of fish. It is done in a plastic caret of about 40 Kg of its capacity.

4)      Salt curing:-

It is traditional method of preservation of fish plasticized as such or in combination with drying or smoking.

Salt curing is an important method of preservation. Main concept regarding this techniques, is when the some amount of salt solution is entered into the fish flesh, it can delay the activity of microorganism or even inactivate them by reducing the water activity by process called “exosmosis” this forms the basis of the salting preservation. Moisture is very necessary to flourish the bacteria at any place.

Concentration of salt at 4-10% level in fish flesh is known to prevent the action of most spoilage bacteria as well as autolytic decomposition. When the concentration of salt is 20% or more in flesh, the decomposition process in the fish proceeds only very slowly.

5)      Smoking / smoke curing:-

Smoking or smoke curing, like drying and salt curing is ancient methods of preservation of fish. In early method of smoking, heavily salted fish used to smoked for long duration and even few weeks and the resultant products were called “hard cures”. This product has long shelf life at ambient temperature. Owing to the high salt concentration and long smoking and drying period, this lowers the water activity considerably.

Smoking is also employed as an intermediate step in processing canned smoked fish. Lightly smoked fish is considered as an alternate to fresh fish having slightly pleasant smoke flavor. In course of time the “hard cures” gave a way to milder production with less salt and lower duration of smoking. Such products however, have short shelf life.

6)      Marinades:-

It is nothing but the preservation of the fish or fish protein processed by treatment with edible acid (acetic acid) and salt and put up in brine, sauce or oils. Fish marinades are characterized by the typical marinades odour and flavor. Treatment with acetic acid and salt brings about a short refinement in fish simultaneously developing typical marinated odors and flavor. Further improvement brought by addition of various spices and covering liquids. Generally pelagic fatty fishes such as sardine, herring etc. used for this preservation method.

Chemical methods of preservation:-

            Chemical methods of preservation is mainly based on the various type of chemical substance either it is organic acid or oxide of metal or non-metal etc. this chemical substance generally acts on the internal physiology of the micro-organism and alter them greatly.

            These chemical substances are as follows,

1)      Organic acid and esters

2)      Nitrite

3)      Sulphur dioxide

1)      Organic acid and esters:-

The most important organic and esters that are used as food preservatives are organic acid such acetic and lactic acid are used for retarding the growth and antimicrobial effect of spoilage organism.

Organic acid and esters are as follows,

1)      Ascorbic acid

2)      Benzoic acid

3)      Acetic acid

4)      Lactic acid

5)      Propionic acid

2)      Nitrite :-

The antibacterial action of nitrite was first described in the 1920. Nitrite is inhibitory to a range of bacteria. Early works showed that a level of 200 mg/ Kg at pH 6.0 is sufficient to stain of E. coli, Micrococcus, pseudomonas and nitrite have ability to inhibit spore forming bacteria such as  C. botolinum bacteria inhibition by nitrite increases with decreasing pH. Nitrite also contributes to the typical cured meat flavor.

3)      Sulphur dioxide:-

Sulphur dioxide has a reputation for its disinfecting properties and its earliest use in the food industry was when sulpher candle were burn to disinfectant the vessel use to produce and store wine. It is also used as an antioxidant and inhibits enzymic and nonenzymic browning reaction in food product.

SO₂ is a reactive molecule can disrupt microbial metabolism in number of ways. As a reducing agent, it can break disulphide linkage in protein and interferes with redox process.