Frozen fish [German version]

Table of contents

General:
Product information
Packaging
Transport
  Container transport
  Cargo securing


Risk factors and loss prevention:
Temperature Odor
Humidity/Moisture Contamination
Ventilation Mechanical influences
Biotic activity Toxicity / Hazards to health
Gases Shrinkage/Shortage
Self-heating / Spontaneous combustion Insect infestation / Diseases




Product information

Product name

German Fisch, gefroren, Gefrierfisch
English Frozen fish
French Poisson congelé
Spanish Pescado congelado
CN/HS number * 03ff.


(* EU Combined Nomenclature/Harmonized System)



Product description

Fish are cold-blooded, aquatic vertebrates. They usually have a streamlined body covered with scales which is divided into head, gill, trunk and tail parts. On the basis of body shape, saltwater fish are divided into round and flat fish. Important saltwater fish include herring, cod, rosefish, mackerel and tuna.

Fish reproduce by spawning, with only a few species bearing live offspring.

Fish is even more perishable than meat. This is attributable not only to the protein-decomposing enzymes which are still active at low temperatures and the large proportion of psychrophilic microorganisms associated with fish, but also to the low connective tissue content of fish. In comparison with lean fish (trout, codling, rosefish or pollack), oily types of fish, such as eel, herring or salmon are particularly at risk of spoilage.

Fish flesh contains on average [22]:

Fish species Protein [%] Oil [%] Water [%]
Eel 12 27 58
Herring 18 5 - 15 65 - 75
Pollack, cod, codling and other lean fish 18 < 1 80
Carp 20 8 77

Fish are frozen by the flash or rapid freezing process, sometimes while still on board the fishing vessels.


Quality / Duration of storage

Quality assessment covers:

size
fleshiness
oil content (for oily fish)


The best quality fish is that frozen by the flash or rapid freezing process. Rapid freezing results in the formation of only very small ice crystals which, unlike large crystals, do not rupture the cell walls and thus do not result in the loss of cell fluids (drip) on thawing.

The following criteria may be used to assess fresh fish: unobtrusive odor, firm and resilient flesh, brilliant red color of gills, bright, glossy color, glossy black pupils.

The fish must be properly deep frozen on loading. If it is not at the required core temperature, it will spoil during a long voyage. Checks must accordingly be carried out during loading. Properly deep frozen fish sounds like wood when struck. The core temperature should be measured for each batch by drilling a hole into the middle of the fish and measuring the temperature with a meat thermometer. In the case of (unpackaged) tuna, a spike is used to make holes 3 - 5 cm in depth in the fish so that the measurement can be made.

Occasionally, fish is delivered which, after freezing, has been exposed to higher temperatures. Such incorrect storage results in depreciation and may be recognized by the formation of frost on the cartons. Fish covered with a thick layer of ice or with brown discoloration or freezer burn must also be rejected prior to loading.

According to [1], the duration of storage for various types of fish is as follows:

Designation Temperature Rel. humidity Max. duration of storage
Frozen oily fish -28 - -18°C 90 - 95% 8 months
Frozen lean fish -20°C 90 - 95% 12 months
Frozen filleted fish -28 - -23°C 90% 6 - 9 months


Frozen fish which has been stored for an excessively long period has a dry, straw-like texture and poor flavor and is described as freezer damaged.

At temperatures of -62°C, the "eutectic point" (EP) is reached Only once the EP is reached is all the water in the cells of the product completely frozen and all microbial decomposition brought to a standstill, i.e. at temperatures of below -62°C it is possible to transport or store foodstuffs for an "infinite" period without loss of quality.


Intended use

Fish is one of the most important sources of dietary protein.


Countries of origin

This Table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.

Europe Germany, France, Portugal, Italy, England, Scotland,
Norway, Finland, Greece, Iceland, Russia
Africa  
Asia Japan, China
America USA, Canada
Australia New Zealand, Australia


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Packaging

Fish, usually packaged in plasticfilm, is transported in cartons or boxes. Oily types of fish should, if possible, be vacuum packaged in an oxygen-impermeable film as there is a risk of rancidity due to the high oil content.

Packaging sizes are so selected that the dimensions of the individual area modules or area module multiples are conformed to the conventional pallet sizes (800x1200 mm and 1000x1200 mm) and cargo units may thus be produced.

Photo, fish

Figure 1



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Transport

Symbols

Symbol, general cargo

General cargo
Symbol, temperature-controlled

Temperature-controlled



Means of transport

Ship, truck, railroad, aircraft


Container transport

Refrigerated containers should be used. Ultra-low temperature refrigerated containers are capable of transporting goods at a temperature of -60°C.


Cargo handling

It is essential to maintain the freezing chain during cargo handling as this is the only way to maintain the storage life and quality of the fish.

In damp weather (rain, snow), the cargo must be protected from moisture, since quality may be diminished.

Because of the cargo's sensitivity to mechanical stresses, it must be handled with appropriate care (breakage).


Stowage factor

approx. 1.68 m3/t (cartons) [1]
2.50 m3/t (boxes, cartons) [11]
1.98 - 2.40 m3/t (boxes) [14]
1.98 - 2.69 m3/t (cartons) [14]
1.98 m3/t (pallets) [14]


Stowage space requirements

Prerefrigerated, dry, neutral in odor


Segregation

Clean, unimpregnated and new fishing nets, fiber rope, thin fiber nets, thin wooden battens


Cargo securing

In order to ensure safe transport, the packages must be stowed and secured in the means of transport in such a manner that they cannot slip or shift during transport. They must not be damaged by other articles or items of cargo.

Photo, fish

Figure 2


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Risk factors and loss prevention

RF Temperature

Frozen fish requires particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

A written cooling order must be obtained from the consignor before loading is begun. This order must always be complied with during the entire transport chain.

The following Table merely constitutes a rough estimate of appropriate temperature ranges. Temperatures may deviate from these values, depending on the particular transport conditions.

Designation Temperature range Source
Travel temperature (favorable temperature range)    
Frozen oily fish -28 - -18°C [1]
Frozen oily fish -29°C [19]
Frozen lean fish -20°C [1]
Frozen filleted fish -28 - -23°C [1]


Since, as a result of the high protein and water content, autolytic processes still proceed at temperatures as low as -10°C, frozen fish must always be at a temperature of below -18°C.

Holds/containers must be appropriately precooled prior to loading. They should be approximately at a temperature of at least -18°C.

The required travel temperature should be maintained at all times because it is only in this way that the activity of microorganisms comes to a standstill and enzymatic degradation processes are largely suppressed. Temperature measurements must be performed and recorded at regular intervals.

The travel temperature must be maintained constantly as variations in temperature may result in recrystallization, resulting in growth of the ice crystals. Variations in temperature are associated with continual slight thawing and refreezing. Since small ice crystals have a higher vapor pressure than larger ones, they will melt more rapidly when the temperature rises, while on cooling the same effect means that the water is preferentially deposited as ice on the larger ice crystals. This consequently brings about growth of the ice crystals, as a result of which the rapidly frozen fish increasingly takes on the appearance of slowly frozen fish on storage. The large ice crystals rupture the cell walls, as a result of which, on thawing, cell fluids (drip) escape, giving rise to a distinct reduction in utility value.

Temperatures lower than specified are not generally harmful, but they should be maintained throughout all the transport operations as there is otherwise a risk of recrystallization.

Photo, fish

Figure 3
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Figure 4
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Figure 5
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Figure 6
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Figure 7


At temperatures of -62°C, the "eutectic point" (EP) is reached Only once the EP is reached is all the water in the cells of the product completely frozen and all microbial decomposition brought to a standstill, i.e. at temperatures of below -62°C it is possible to transport or store foodstuffs for an "infinite" period without loss of quality.


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RF Humidity/Moisture

Frozen fish requires particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

Designation Humidity/water content Source
Relative humidity approx. 90 - 95% [1]
Water content 65 - 80% [1]
Maximum equilibrium moisture content approx. 90% [1]


Higher relative humidity may be permitted for frozen goods because the low temperatures mean that microbial growth is no longer possible.

Relative humidity in the hold/container should be kept at 95% in order to prevent the surface of the fish from drying out (freezer burn), an effect which may also be counteracted by plastic film packaging.


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RF Ventilation

Frozen fish requires particular temperature, humidity/moisture and ventilation conditions (SC VII) (storage climate conditions).

Recommended ventilation conditions: circulating air, 6 circulations/hour without supply of fresh air in order to ensure uniform cooling of all parts of the cargo.


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RF Biotic activity

Frozen fish displays 3rd order biotic activity.

It belongs to the class of goods in which respiration processes are suspended, but in which biochemical, microbial and other decomposition processes, which must be taken into account, still proceed.

At temperatures of -62°C, the "eutectic point" (EP) is reached Only once the EP is reached is all the water in the cells of the product completely frozen and all microbial decomposition brought to a standstill, i.e. at temperatures of below -62°C it is possible to transport or store foodstuffs for an "infinite" period without loss of quality.


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RF Gases

No risk.


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RF Self-heating / Spontaneous combustion

No risk.


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RF Odor

Active behavior Frozen fish has a very slight, unpleasant odor. It must, on principle, be stowed alone in a means of transport as odor tainting must always be expected, even when the product is packaged in plastic film and cartons.
Passive behavior It is highly odor-sensitive and very rapidly absorbs foreign odors.



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RF Contamination

Active behavior Frozen fish does not cause contamination.
Passive behavior Frozen fish is extremely sensitive to contamination. Holds/containers must therefore be clean and in a thoroughly hygienic condition. It is recommended that fitness for loading of the hold/container be confirmed by an inspector.



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RF Mechanical influences

Fish packaged in cartons must be secured in the hold or container in such a way that it cannot move during transport. In the case of container transport, it is also important for the goods to be secured in the door area so that they cannot fall out of the container when the doors are opened.


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RF Toxicity / Hazards to health

Some types of fish contain natural toxins, such as the toxin of the puffer or porcupine fish, which is not destroyed even by boiling. The toxic body parts of these fishes must accordingly be removed immediately.

Toxic breakdown products may also be formed which may be hazardous to humans.


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RF Shrinkage/Shortage

Weight loss of approx. 1 - 2% may occur during transport.


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RF Insect infestation / Diseases

If the specified temperature and humidity conditions are maintained, microorganisms constitute no risk as their activity comes to a standstill at approx. -10°C.

Care must be taken to ensure that the gills have been removed from tuna as they may undergo spoilage even at low temperatures.

Sea and freshwater fish may be attacked by internal parasitic worms. Filleted fish must not contain any parasites.

As a basic principle, a veterinary certificate is required for transport operations.


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