Difference between revisions of "Fish, frozen"
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If the cargo is in store, the surveyor should take into account the manner of discharge and delivery to the store, in case these operations could have affected the quality of the product or could in themselves be responsible for any damage.<br><br>
If the cargo is in store, the surveyor should take into account the manner of discharge and delivery to the store, in case these operations could have affected the quality of the product or could in themselves be responsible for any damage.<br><br>
Latest revision as of 11:36, 24 May 2019
|Infobox on Fish, frozen|
|Example of Fish, frozen|
|Origin||This table shows only a selection of the most important countries of origin and should not be thought of as exhaustive.|
|Stowage factor (in m3/t)|
|Humidity / moisture|
|Ventilation||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.|
|Risk factors||See text under heading ‘Damage to fish’|
The term fish processing refers to the processes associated with fish and fish products between the time fish are caught or harvested, and the time the final product is delivered to the customer. Although the term refers specifically to fish, in practice it is extended to cover any aquatic organisms harvested for commercial purposes, whether caught in wild fisheries or harvested from aquaculture or fish farming.
Larger fish processing companies often operate their own fishing fleets or farming operations. The products of the fish industry are usually sold to grocery chains or to intermediaries. Fish are highly perishable. A central concern of fish processing is to prevent fish from deteriorating, and this remains an underlying concern during other processing operations.
Fish processing can be subdivided into fish handling, which is the preliminary processing of raw fish, and the manufacture of fish products. Another natural subdivision is into primary processing involved in the filleting and freezing of fresh fish for onward distribution to fresh fish retail and catering outlets, and the secondary processing that produces chilled, frozen and canned products for the retail and catering trades.
Fish is a highly perishable food which needs proper handling and preservation if it is to have a long shelf life and retain a desirable quality and nutritional value. The central concern of fish processing is to prevent fish from deteriorating. The most obvious method for preserving the quality of fish is to keep them alive until they are ready for cooking and eating. For thousands of years, China achieved this through the aquaculture of carp. Other methods used to preserve fish and fish products include:
- The control of temperature using ice, refrigeration or freezing
- The control of water activity by drying, salting, smoking or freeze-drying
- The physical control of microbial loads through microwave heating or ionizing irradiation
- The chemical control of microbial loads by adding acids
- Oxygen deprivation, such as vacuum packing
Usually more than one of these methods is used. When chilled or frozen fish or fish products are transported by road, rail, sea or air, the cold chain must be maintained. This requires insulated containers or transport vehicles and adequate refrigeration. Modern shipping containers can combine refrigeration with a controlled atmosphere.
Fish processing is also concerned with proper waste management and with adding value to fish products. There is an increasing demand for ready to eat fish products, or products that don't need much preparation
When fish are captured or harvested for commercial purposes, they need some preprocessing so they can be delivered to the next part of the marketing chain in a fresh and undamaged condition. This means, for example, that fish caught by a fishing vessel need handling so they can be stored safely until the boat lands the fish on shore. Typical handling processes are:
- Transferring the catch from the fishing gear (such as a trawl, net or fishing line) to the fishing vessel
- Holding the catch before further handling
- Sorting and grading
- Bleeding, gutting and washing
- Storing the chilled fish
- Unloading, or landing the fish when the fishing vessel returns to port
The number and order in which these operations are undertaken varies with the fish species and the type of fishing gear used to catch it, as well as how large the fishing vessel is and how long it is at sea, and the nature of the market it is supplying. Catch processing operations can be manual or automated. The equipment and procedures in modern industrial fisheries are designed to reduce the rough handling of fish, heavy manual lifting and unsuitable working positions which might result in injuries.
If the temperature is decreased, the metabolic activity in the fish from microbial or autolytic processes can be reduced or stopped. This is achieved by refrigeration where the temperature is dropped to about 0 °C, or freezing where the temperature is dropped below -18°C. On fishing vessels, the fish are refrigerated mechanically by circulating cold air or by packing the fish in boxes with ice. Forage fish, which are often caught in large numbers, are usually chilled with refrigerated or chilled seawater. Once chilled or frozen, the fish need further cooling to maintain the low temperature. There are key issues with fish cold store design and management, such as how large and energy efficient they are, and the way they are insulated and palletized.
An effective method of preserving the freshness of fish is to chill with ice by distributing ice uniformly around the fish. It is a safe cooling method that keeps the fish moist and in an easily stored form suitable for transport. It has become widely used since the development of mechanical refrigeration, which makes ice easy and cheap to produce. Ice is produced in various shapes; crushed ice and ice flakes, plates, tubes and blocks are commonly used to cool fish. Particularly effective is slurry ice, made from micro crystals of ice formed and suspended within a solution of water and a freezing point depressant, such as common salt.
A more recent development is pumpable ice technology. Pumpable ice flows like water, and because it is homogeneous, it cools fish faster than fresh water solid ice methods and eliminates freeze burns. It complies with HACCP and ISO food safety and public health standards, and uses less energy than conventional fresh water solid ice technologies.
The water activity in a fish is defined as the ratio of the water vapour pressure in the flesh of the fish to the vapour pressure of pure water at the same temperature and pressure. It ranges between 0 and 1, and is a parameter that measures how available the water is in the flesh of the fish. Available water is necessary for the microbial and enzymatic reactions involved in spoilage. There are a number of techniques that have been or are used to tie up the available water or remove it by reducing the aw. Traditionally, techniques such as drying, salting and smoking have been used, and have been used for thousands of years. These techniques can be very simple, for example, by using solar drying. In more recent times, freeze-drying, water binding humectants, and fully automated equipment with temperature and humidity control have been added. Often a combination of these techniques is used.
Fish is transported widely in ships, and by land and air, and much fish is traded internationally. It is traded live, fresh, frozen, cured and canned. Live, fresh and frozen fish need special care.
When live fish are transported they need oxygen, and the carbon dioxide and ammonia that result from respiration must not be allowed to build up. Most fish transported live are placed in water supersaturated with oxygen (though catfish can breathe air directly through their gills and body skin, and the climbing perch has special air-breathing organs). The fish are often "conditioned" (starved) before they are transported to reduce their metabolism and increase packing density, and the water can be cooled to further reduce metabolism. Live crustaceans can be packed in wet sawdust to keep the air humid.
Over five percent of the global fish production is transported by air. Air transport needs special care in preparation and handling and careful scheduling. Airline transport hubs often require cargo transfers under their own tight schedules. This can influence when the product is delivered, and consequently the condition it is in when it is delivered. The air shipment of leaking seafood packages causes corrosion damage to aircraft, and each year, in the US, requires millions of dollars to repair the damage. Most airlines prefer fish that is packed in dry ice or gel, and not packed in ice.
By land or sea
"The most challenging aspect of fish transportation by sea or by road is the maintenance of the cold chain, for fresh, chilled and frozen products and the optimisation of the packing and stowage density. Maintaining the cold chain requires the use of insulated containers or transport vehicles and adequate quantities of coolants or mechanical refrigeration. Continuous temperature monitors are used to provide evidence that the cold chain has not been broken during transportation. Excellent development in food packaging and handling allow rapid and efficient loading, transport and unloading of fish and fishery products by road or by sea. Also, transport of fish by sea allows for the use of special containers that carry fish under vacuum, modified or controlled atmosphere, combined with refrigeration."
Quality and safety
The International Organization for Standardisation, ISO, is the worldwide federation of national standards bodies. ISO defines quality as "the totality of features and characteristics of a product or service that bear on its ability to satisfy stated or implied needs."(ISO 8402). The quality of fish and fish products depends on safe and hygienic practices. Outbreaks of fish-borne illnesses are reduced if appropriate practices are followed when handling, manufacturing, refrigerating and transporting fish and fish products. Ensuring standards of quality and safety are high also minimizes the post-harvest losses."
The fishing industry must ensure that their fish handling, processing and transportation facilities meet requisite standards. Adequate training of both industry and control authority staff must be provided by support institutions, and channels for feedback from consumers established. Ensuring high standards for quality and safety is good economics, minimizing losses that result from spoilage, damage to trade and from illness among consumers."
Fish processing highly involves very strict controls and measurements in order to ensure that all processing stages have been carried out hygienically. Thus, all fish processing companies are highly recommended to join a certain type of food safety system. One of the certifications that are commonly known is the Hazard Analysis Critical Control Points (HACCP). Hazard Analysis and Critical Control Points.
HACCP is a system which identifies hazards and implements measures for their control. It was first developed in 1960 by NASA to ensure food safety for the manned space program. The main objectives of NASA were to prevent food safety problems and control food borne diseases. HACCP has been widely used by food industry since the late 1970 and now it is internationally recognized as the best system for ensuring food safety.
The Hazard Analysis and Critical Control Points (HACCP) system of assuring food safety and quality has now gained worldwide recognition as the most cost-effective and reliable system available. It is based on the identification of risks, minimizing those risks through the design and layout of the physical environment in which high standards of hygiene can be assured, sets measurable standards and establishes monitoring systems. HACCP also establishes procedures for verifying that the system is working effectively. HACCP is a sufficiently flexible system to be successfully applied at all critical stages -- from harvesting of fish to reaching the consumer. For such a system to work successfully, all stakeholders must cooperate which entails increasing the national capacity for introducing and maintaining HACCP measures. The system's control authority needs to design and implement the system, ensuring that monitoring and corrective measures are put in place."
HACCP is endorsed by the:
- FAO (Food and Agriculture Organization)
- Codex Alimentarius (a commission of the United Nations)
- FDA (US Food and Drug Administration)
- European Union
- WHO (World Health Organization)
There are seven basic principles:
- Principle 1: Conduct a hazard analysis.
- Principle 2: After assessing all the processing steps, the Critical control point (CCP) is controlled. CCP are points which determine and control significant hazards in a food manufacturing process.
- Principle 3: Set up critical limits in order to ensure that the hazard identified is being controlled effectively.
- Principle 4: Establish a system so as to monitor the CCP.
- Principle 5: Establish corrective actions where the critical limit has not been met. Appropriate actions need to be taken which can be on a short or long-term basis. All records must be sustained accurately.
- Principle 6: Establish authentication procedures so as to confirm if the principles imposed by HACCP documents are being respected effectively and all records are being taken.
- Principle 7: Analyze if the HACCP plan are working effectively.
Shipment / storage
The best quality fish is that frozen by a rapid freezing process, which results in the only very small ice crystals formation. Unlike large crystals, these do not rupture the cell walls and thus do not result in the loss of cell fluids (drip) on thawing.
Fresh fish criteria are: unobtrusive odor, firm and resilient flesh, brilliant red color of gills, bright, glossy color, glossy black pupils.
If fish is not properly deep frozen resp. not at the required core temperature upon loading, 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.
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 should also be rejected prior to loading.
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, whereby all the water in the cells of the product is 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.
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. Ultra-low temperature refrigerated containers are capable of transporting goods at a temperature of -60°C. 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.
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. If the specified temperature and humidity conditions are maintained, microorganisms constitute no risk as their activity comes to a standstill at approx. -10°C.
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.
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.
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.
Damage to fish
Damage to fish is often due to their not being sound and properly cured before loading. Too much heat can cause development of ‘skin heat’ (boiled, burned) distinguished by loosening of the skin. This type of damage may occur on wet-salted or partly dried fish. Wet-salted and dried fish may develop a disease known variously as ‘Pink’, ‘Pink Eye’ or ‘Redmite’. It may be caused by humidity, etc., but is commonly stated to exist in certain salts. Pink discoloration is inherent and may appear during curing or transit. These organisms do not grow below a temperature of approx. 5°C, but the rate of growth is very sensitive to temperatures above this figure. Tails and fins of sun-cured fish may resemble glue to the touch due to over-exposure to the sun.
Dried fish is sometimes used as a fertiliser, and when shipped for this purpose, if wetted, should be spread and dried promptly; the nitrogen content should not then be affected.
Mixing with ice or chilling has limitations as a method of preserving the quality of newly caught fish. The more commercially important species of white fish, e.g. cod, haddock, hake, etc., cannot be kept in a reasonably fresh condition for more than 10-12 days from the time of catching when stowed in crushed ice. In the cases of herrings and similar fatty fish the period is even shorter. The quality of frozen fish can be adversely affected by very slow freezing and in the case of ‘unglazed’ fish, storage at too high a temperature will affect the fish. It should be borne in mind that the most perfect of cold storage conditions cannot improve the quality of the fish, it can only fix the quality at the time of freezing.
If the fish is put into cold store within a short period after catching there should be no deterioration due to cold storage. If, however, the raw material is not so fresh, or is stale, some deterioration must be expected even under the best conditions of cold storage. Spoilage may occur if thawed fish is re-frozen. Temporary rises in temperature above -18°C may lead to effective storage times being reduced.
Quite often fish is sent on long voyages at temperatures in the region of -10°C. Shipment under such conditions would limit the storage life of the fish, and on long voyages such fish would be reaching a state of inedibility. To avoid this, the core temperature of the fish at time of loading should be below -18°C. For fish with a large fat content, e.g. herring, the loading temperature should be at least -21°C. These temperatures should be maintained throughout the voyage. Temperatures of -30°C are essential if fish are to be kept for a period of many months in the same condition as when they were caught.
The quality of frozen fishery products
Quality of products
Complaints about defects in the quality of frozen fishery cargoes usually fall into one or both of two categories:
- Abnormal and offensive odours, flavours or texture, or any other defects that will influence the consumer’s perception of quality.
- Physical damage affecting the process ability or merchantability of the product (can occur during the freezing process, though more usually happens during handling of the frozen product).
Quality defects in both categories can arise during handling, processing and storage of the product before delivery to the vessel, during loading into the ship’s holds, and while the product is stored on the reefer.
Loss of quality can occur both before and after freezing. However, the nature of the defects differs in the two circumstances and an experienced assessor should be able to distinguish between them.
Loss of quality before freezing
Fish of all kinds are notorious for the speed at which they spoil (even when chilled) and for the unpleasant nature of the spoiled product. Spoilage affects the appearance, odour and flavour of the product. Freezing halts the spoilage process and fixes the quality as it was at the time of freezing. When frozen products are thawed out, the quality can be no better than it was at the time of freezing. If defects in the quality of frozen fishery products at time of delivery are shown to be a consequence of spoilage, then no blame can be attached to the carrier of the frozen goods unless the product had thawed out during the voyage.
Loss of quality during frozen storage
Frozen fishery products are not completely stable in the frozen state and will deteriorate over time, resulting in changes in texture, odour and flavour of the product. Changes in texture are similar in character across most fishery products – the product becomes dry, stringy and tough. But changes in odour and flavour depend on the type of fishery product. Lean fish with low oil content (such as cod) develop the characteristic odours and flavours described as ‘musty’, ‘cardboard’, and ‘wet dog’, while fish with high oil contents (like tuna, herring and mackerel) develop rancid odours and flavour reminiscent of new leather, linseed oil or old-fashioned oil paints. Odour and flavour changed in frozen crustacean shellfish and cephalopods are similar to those in lean fish. Oily fish deteriorate faster, and produce off-odours more quickly than lean fish during frozen storage.
The main factors influencing the rate at which fishery products deteriorate during frozen storage are temperature of storage and exposure to air. The lower the storage temperature, the slower the product deteriorates. The storage life of fishery products carried at -18°C ranges from 3 to 12 months. In general, storage life is halved for each 5°C rise in storage temperature. For example, a product with a storage life of 8 months at -18°C will have a storage life of 4 months at -13°C. Since ships’ refrigeration systems can maintain products at temperatures below -18°C, and since voyages are generally less than a month long, there should be no significant loss of quality due to frozen storage-related defects during a voyage.
Rate of deterioration is also affected by exposure to air. Block-frozen products are usually protected by close wrapping with plastic film or by coating with a water glaze. To maintain quality, it is important that this cover, film or glaze is not damaged or lost.
Another defect arising during frozen storage is excessive loss of moisture from the product, which leads to general or localised dehydration known as freezer burn. The dehydration is signified by white patches which appear where glaze is lost or where there are tears or breaks in the protective wrapping. In unprotected material, dehydration occurs first in thin parts of the product such as the fins of whole fish and the tail ends of fillets, or at the corners of blocks. These dried areas do not re-hydrate when the product is thawed and are indicated by blemishes in the thawed product.
Physical damage to frozen products
Physical damage takes a number of forms, but complaints about the quality of reefer cargoes are usually concerned with distortion or compression of the product. This kind of damage, which affects individually frozen fish or blocks of products, occurs when warm fishery products (i.e. warm relative to the recommended storage temperature) are subjected to pressure, for example in a stack of fish stored in a ship’s hold.
When water is frozen it changes from a liquid to a hard solid ice at 0°C. Although fish typically contain 70-80% of water – the exact percentage depends on the species – the situation is more complicated than freezing water alone. Water in the fish tissues starts to freeze at about -1°C but at this point only a proportion of the water is converted to ice. Progressively, more water freezes as the temperature falls. At -18°C, the maximum temperature usually specified for carriage of frozen fish in reefers, around 90% of the water has turned to ice. It is very hard to deform fish at this temperature and below except under extremely high pressure.
If the product warms at all, some of the ice melts. The fish tissue holds an increasing proportion of liquid water and a decreasing proportion of ice as its temperature rises. As the proportion of ice decreases, the fish tissue, though still partly frozen, becomes softer and can be deformed by moderate pressure. For example, it is possible to deform the surface of a product at -7°C by pressing hard with the point of a pen, a temperature probe, or even a thumbnail.
At -3°C, ‘frozen’ fishery products are soft enough to deform and sag under their own weight. If the cargo in the hold of a reefer is stacked to a height of 4 or 5 metres, as is often the case, there is sufficient pressure to distort fish to some extent at -7°C, and to distort and compress fish considerably at -5°C or higher.
Individually frozen fish can be severely indented where they lie across each other, and tend to take up the shapes of the surfaces they are pressed against – ridged floor plates or edged structures in the hold. In an extreme case, a stack of fish can be compressed together into a solid mass, with almost no spaces between the fish. Blocks of products are squeezed, flattened and distorted and will extrude into gaps between cartons. They can also be indented by floor plates or pallet boards.
Frozen products at low temperatures are often brittle and prone to damage by rough handling. For example, tails are easily broken off whole fish and blocks can be shattered or chipped. Products can also be damaged by contamination. If oil or chemicals are spilled, they may penetrate the wrappings and affect the contents. When cartons and wrappings are torn, the contents are more vulnerable to both contamination and dehydration.
Loss of quality in fishery products can be caused by damage both before and after freezing. Carriage of frozen fish by sea is just one stage in a long sequence of processing, handling, distribution and storage operations – products can be damaged or decline in quality at any stage. Receivers of damaged cargoes of frozen fishery products might allege that loss of quality occurred solely while the material was in the charge of the shipowner. Pre-shipment inspection is therefore essential, to determine as far as possible the condition and quality of the product at the time of loading, and to note any circumstances that could lead to an exaggerated loss of quality during carriage in the vessel. Such information has an important bearing on any claim that loss of quality or damage occurred during carriage in the reefer. The inspection should take into account the nature of the material, its packaging and its presentation.
Pre-shipment inspection by the ship’s officers is generally restricted to visual inspection of the cargo and to measurement of physical properties such as temperature. Officers are not expected to carry out detailed evaluations of the quality of the material, which would require examination of material after thawing and perhaps also after cooking.
Nature of the consignment
The deck crew should check that the material to be loaded is consistent with the bill of lading. However, information provided on a bill of lading is usually very brief – a cargo may be described as ‘fishery products’, which encompasses many different product types. Wherever possible, deck officers should record any additional information, for example, in the case of individually frozen fish, the species or variety, the presentation (whole or dressed) and the name of the fishing vessel.
It is also important to record details of any labelling on wrapped or cartonned material, particularly production dates or batch codes. The absence of any labelling, particularly of batch or production codes, should also be noted.
Information on the nature of the consignment and all details of labelling should be recorded on the mate’s receipt. If labels are detachable, one can be removed and attached to the receipt.
Temperature of the consignment
It is essential to measure the temperature of frozen fish presented for loading. Since fishery products suffer damage if they are stowed at a high temperature, temperature records provide important evidence of the state of the product at the time of loading. The terms of carriage normally stipulate the temperature, or at least the maximum temperature, at which the cargo should be carried. Holds of reefer vessels are intended for storage of frozen material loaded at the required temperature of carriage. Refrigeration systems have little space capacity to lower the temperature of products which are put into the hold at above its operating temperature. Material that is above the operating temperature of the hold will take a long time to cool down and will lose quality as a result.
The terms of contract between the provider of the frozen products and the recipient sometimes specify the maximum temperature at which the products should be stored and delivered to the reefer – a maximum temperature of -10°C would be typical for frozen tuna delivered from a tuna fishing vessel. Even if there is no specific requirement for the cargo’s temperature on delivery to the vessel, the master may refuse to accept a product if he considers the temperature too high and the product at risk of damage during stowage and carriage.
The deck officer should ensure that sufficient measurements are taken to provide an adequate summary of the temperature of the cargo, and that the measurements are accurately recorded.
During loading, supervising officers should note any softening of the flesh of fish during transfer to the vessel – this can be gauged by pressing the surface of the fish with a thumb nail or the point of a temperature probe. Even when the temperature measured at the core of a fish is low, the flesh on the outside can be soft enough to be damaged by the pressure of a stack within a hold.
Condition of the material
It is not easy to assess the intrinsic quality of frozen products by visual examination, but, with experience, one can get some indication of pre-freezing quality from the appearance of the eyes and skin in the case of whole fish, from the colour of the shell in the case of shell-on crustacean shellfish, and from the colour of the skin in the case of cephalopods. Of course, these indications of quality will not be visible in packaged products unless some of the cartons are opened. Whenever possible, photographs should be taken of any defects.
Visual indications of spoilage in individually frozen fish
The inspecting officer should examine frozen fish individually for signs of spoilage before freezing. The beneath summarises the difference in appearance between good quality and stale fish
|Good quality fish||Stale fish|
|Colours||Bright, demarcated||Degraded and dull|
|Eyes||Clear or slightly cloudy; flat to the head or even projecting slightly||Yellowish or reddish, sunken or missing|
|Skin||Clean – no discoloured slime or coating||Abraded and covered with yellowish slime or blood-stained brine; head region of tuna takes on a diffuse pinkish hue|
Nature and integrity of packaging and wrapping
Packaging is intended to protect the product from physical damage. The inspecting officer should record any damage to outer wrappings, particularly if the damage has caused exposure of the contents. Sometimes the packaging includes strapping, particularly where a carton contains individually wrapped, heavy products like blocks of fillets. The nature and integrity of any strapping should be noted.
Wrapping, which may or may not be supplemented by further packaging in a carton, is intended to prevent contamination and dehydration. Wrapping is only effective in protecting against dehydration if it is sealed or is closely applied to the product. The record should include details of the type and condition of any wrapping. The officer should note any staining of cartons and outer wrappings, including the character and nature of the stain – lubricating oil, fuel oil, water, fish juices, for example. Oils tend to be dark in colour and leave the wrappings soft, even when frozen; fish-juice stains are yellowish or reddish. The officer should note if the staining is extensive, covering all or most of the packaging or wrappings, or localised. When stains are localised, note whether they are predominantly on corners or edges of packages or on the sides.
Blemishes, stains and contamination of the product
When the surface of the product is visible, it should be inspected for blemishes and contamination. Blemishes include surface damage to whole fish like abrasions and tears to the skin or splits in the flesh, and surface damage to blocks such as patches of freezer burn. An attempt should be made to assess the proportion of the consignment affected. It is important to record any unusual discolouration or staining, and if possible the nature of the defect, for example, blood or bloody brine (particularly on brine-frozen tuna), oil and chemicals. The product should also be examined for contamination by dust, organic matter such as fish offal or vegetable debris, and any other foreign matter. In all cases of blemishes or contamination, the inspecting officer should note the extent of the damage and estimate the proportion of the consignment affected.
Signs of thawing or partial thawing
Sometimes claims are made against shipowners on the basis that a cargo had thawed or partially thawed during the voyage, and had then frozen again to the stipulated carriage temperature. It is therefore important to check that a potential cargo does not show signs that it had thawed and refrozen before it had been presented for shipment. Such thawing or near thawing is often indicated by distortion of product shape and release of liquids from the product.
Distortion of whole or blocks of fish indicates that the material has thawed or partially thawed since freezing, or was distorted during the freezing process. Individually frozen whole fish often have slight pressure marks formed during the freezing process. These minor distortions must be allowed for during examination of frozen products. The nature of the marks depends on the freezing process. For example, fish frozen in trays are slightly flattened or have indentations on one side where they have lain on the trays during freezing.
Brine frozen fish tend to float in the brine tanks and are restrained below the level of the brine by a grating. As a result, the fish may have slightly flattened sides where they have been compressed, or shallow cylindrical-shaped depressions where fish lay across each other as they froze. Sometimes the pressure on tuna during brine freezing results in splitting of the skin and flesh, usually on the dorsal surface at the base of the dorsal fin. Any splitting should be noted by the officer. Any distortions other than slight flattening or the presence of minor depressions suggest that the product has warmed up, softened and refrozen in the distorted shape. The officer should note the nature and extent of any distortions.
Blocks of fish should reflect the sharp angles and regular, geometrical shape of the tray or former in which they were frozen. Blocks of fish which have thawed whilst stored on pallets or in stacks show signs of slumping, bending, or compression, and material is often squeezed into spaces between blocks.
Restrains such as strappings and the framing of pallets and shelf supports cause indentations in the blocks of fish. Again, the inspecting officer should note the nature and extent of distortions.
Release of liquid
Fish release liquid as they thaw. The officer should check for pools of liquid collecting within wrappings, and for signs that liquid has been squeezed from the blocks and has refrozen on the sides of the stack or on shelves and pallets. Staining of cartons is sometimes an indication that the contents have thawed and released liquid.
Transfer, stowage and carriage
Temperature control during loading
It is very important for maintaining quality that frozen fishery products be held at low temperatures at all times. Although it is inevitable that the product’s temperature will rise during loading into the hold, the loading operations must be conducted so as to keep this rise to a minimum. The product’s quality suffers not only due to the immediate rise in temperature as material is stowed in the hold, but also because of the time taken to bring the product back down to the required temperature after stowage.
As far as possible, the cargo should be loaded at, or below, the required temperature of carriage – typically around -18°C. Officers and crew should attempt to minimise warming of the cargo while it is being loaded and stowed in the holds, preferably so that the temperature of the cargo is not above -12°C by the time it is stowed. Although the ship’s crew may have little control over loading operations, the master should cooperate with the ship’s agents, and particularly with the stevedoring company, to ensure that good practices are adopted during loading and stowing.
Good practices during loading:
- Ensure that delivery to the ship’s side is matched to loading into the vessel to reduce the time that products are waiting on the quay.
- Products should be delivered in insulated containers or lorries, or at least in covered vehicles.
- If the material must be unloaded onto the quay or held on the deck of the reefer, it should be placed on pallets or on an insulating base, packed as tightly as possible and covered with a tarpaulin or similar protection against sun and wind.
- The cargo should be protected from exposure to wind, rain and sun until it is about to be transferred to the vessel.
- In tropical climates, avoid loading for two or three hours either side of noon and consider loading the vessel at night.
Good practices during stowage:
- Ensure that the hold is cooled to below the carriage temperature before loading begins.
- During breaks in loading, cover holds or decks with at least the hatchcovers, even if the thermal covers are not put in place.
- Refrigeration to the holds should be turned on during long breaks.
- Transfer cargo as rapidly as possible from the quay to the vessel’s hold.
- Once loaded, the cargo should be covered with tarpaulins.
- Where consistent with efficient loading, use only one hatch at a time to avoid through currents of air in the hold.
Maintaining low temperatures during carriage
There is usually an explicit or implicit requirement to hold the cargo below -18°C during carriage. The ship’s refrigeration system must be capable of delivering air to the holds at a temperature a few degrees below the target temperature to allow for heat leaks through the ship’s structures. Cargo spaces in reefers are usually cooled by recirculating air systems, which are only effective if the air can circulate freely through and around the stow.
Most heat leaks into the cargo hold occur through the sides and bulkheads, and it is important to ensure that there is free circulation between the cargo and the structures of the hold. Sides and bulkheads should be fitted with vertical dunnage (without horizontal battens which could obstruct air flow) to keep the cargo away from the structures. There should be an even gap of at least 20 cm between the top of the stowed cargo and the lowest part of the deckhead.
Cartons should be stacked with gaps between them, while stows of individually frozen fish will inevitably have spaces between the fish unless the fish are deformable and have been compressed.
The ship’s engineer should ensure that refrigeration equipment is well maintained and can achieve the design temperatures. Evaporator coils must be defrosted as required to maintain the cooling capacity. Frequent need for defrosting is a sign of high temperatures in the cargo and should be noted in the engine room log. In addition, the engine room log should record temperatures at critical and meaningful positions in the refrigeration system – for example, the outlet and return air streams in air cooling systems, and the outlet and return fluid temperatures in pipe-cooled systems.
It is vital to take and record temperature measurements in the hold. How meaningful these measurements are depends on the location of the temperature sensors. Material in the centre of the stow is the slowest to cool because the source of refrigeration is mainly around the sides of the stow. Refrigerated air percolates gaps between fish or between cartons and the cooling effect depends very much on the existence of uninterrupted spaces. Sensors attached to the sides or bulkheads of the hold are exposed to cold air circulating through the dunnage against the sides or bulkheads and therefore tend to indicate temperatures lower than the bulk of the cargo. Sensors should be attached to posts or other structural members running through the hold, where they are more likely to reflect the temperature of the bulk of the cargo accurately.
Protecting the cargo from contamination
Every effort must be made to protect the cargo from contamination. Good shipboard practices will prevent direct contamination by seawater, bilge water, fuel oil and the like, but it is important to be aware that fishery products are rapidly tainted by odours picked up from the ambient air. This is a vital consideration when using air-cooled refrigeration systems – the air must not become polluted by odoriferous materials such as fuel oil, paints or chemicals used on the ship. A simple guideline is that if the air circulating through the hold has an odour, then that odour will be picked up by the fish products.
When a cargo is unloaded from the ship, similar precautions should be taken to those recommended during loading to minimise warming. Unloading should be completed as quickly as possible and the cargo should be protected from wind, rain and high temperature.
The importance of documents
Documents are fundamentally important in the investigation of any claim involving damage to the cargo. They will be examined by the surveyors, and may be used as evidence in any subsequent legal proceedings. The following documents are likely to be important in the event of a claim:
- Ship’s general particulars
- Crew list
- Pre-loading port survey
- Bill(s) of Lading
- Mate’s receipt(s)
- List of remarks
- Statement of facts loading port
- Carrying instructions
- Stowage plan
- List of cargo temperatures during loading and in transit
- Ship’s deck-logbook
- Ship’s reefer logbook
- Last sensoric ice-test
- RMC (Refrigerated Machinery Certificate)
- Sea protest (if any)
- Any documentation arising from disputes/complaints during loading/discharge/transit of the cargo
In addition, photographs can provide important evidence in support of statements in the logs and inspection reports.
The mate’s receipts should include the record of the pre-shipment inspection. This record should detail all observations on the cargo’s condition at time of receipt, including results of at least a visual inspection of each part of the consignment. Records should also include temperature measurements, taken at sufficiently frequent intervals to provide a fair indication of the average temperature of the cargo.
Any observations which indicate that cargo temperature is high, or that cargo was delivered in a damaged or deteriorated condition, should be supported as far as possible by further evidence. This evidence might include photographs taken during pre-shipment inspection or results of reports by cargo surveyors. The mate’s receipt should include any information on the nature of the consignment supplementary to the bill of lading, as well as details of any labels/marks/numbers.
Deck log for loading and unloading
Many charter-party agreements specify a minimum rate of transhipment or loading. To demonstrate compliance with this, and to provide evidence in case of claims concerning damage to the cargo during loading, the timing and sequence of events during loading should be noted in the deck log. At minimum, the log record should include the following:
- Pre-cooling particulars
- Where cargo was loaded from – quay, lighter, fishing vessel, etc.
- Times of opening and closing of hatches
- Arrival and departure of stevedores on board
- Times when the refrigeration system was turned on and off
- Start and finish of cargo stowage
- Any breaks in loading
- Weather conditions (sun, wind, rain, ambient temperature)
- Any unusual or irregular events which might affect the condition of the cargo during stowage or subsequent carriage
Normally, unloading is the responsibility of the receiver, and the master of the vessel may consider that his responsibility for the cargo is over. However, the deck log should continue to record conditions during discharge, logging similar information as listed above for loading.
A stowage plan should be drawn up for all cargoes – an accurate plan is a central piece of evidence in any damage claims arising against the vessel. The stowage plan should indicate the location of each consignment and part of consignment and should include the following information:
- Number of units (pallets, cartons or blocks) in each location/compartment
- Gross and net weight
- Port of loading/destination
- Corresponding bill(s) of lading
The Reefer logbook is one of the most important documents, since it contributes evidence about the temperature of the ship’s cargo during stowage and carriage. The log should document at least the following:
- Temperatures at the sensors (supply/return)
- Temperatures at the sensors in the hold (USDA system)
- Times when compressors were turned on and off
- Defrost periods
Actions in case of dispute
Action by the master of the vessel
The master must load the cargo in apparent good order and condition and act to maintain it in this state. This section describes actions to be taken when a potential problem is identified. In the event of any concern or dispute over the condition of the cargo while loading or unloading, the master of the vessel should contact his owners or charterers or his P&I correspondent. Best practice would indicate that loading or unloading should cease until instructions have been received, although this may not always be possible.
As soon as any question is raised over the condition of the cargo, the ship’s master should begin to document the events surrounding the discovery of defective material, and the nature and possible extent of the alleged defects.
If possible, loading or unloading of the vessel should be halted and the hatches closed until a cargo surveyor is present. Ideally, cargo should be inspected and sampled while still in the hold, or even during discharge, allowing the surveyor to determine if the nature and extent of the damage is in any way related to position in the hold.
Once the cargo has been discharged into store, relating damage to location in the hold is obviously more difficult, or impossible, unless the cargo is adequately labelled. Therefore, if loading or unloading must continue, the master should ensure that each cargo unit is labelled with the hatch number and deck, as well as location within the hatch and deck, as it leaves the hold. The deck log should also record the destination of the material and the agent responsible for handling it.
The master should ensure that all records and documents relevant to the dispute are secure, and that they are only made available to parties representing the ship’s interests.
Services of surveyors
When a problem is identified during loading or unloading - for example, if the temperature of the material is too high – loading or unloading should cease until the cargo has been inspected by a specialist surveyor.
If the dispute concerns the condition of the product, it will probably be necessary to call in at least one specialist surveyor to examine the cargo, establish its current condition and determine the nature and cause of any defects.
If it is suspected that defects result from maritime causes – for example, physical damage from movement of cargo, or from contamination with seawater, fuel oil or bilge water – an expert in ship operations should be called in. However, if the defects could be attributed to the initial quality of the material when loaded, or to the way the product was stowed and carried on the vessel, a specialist surveyor would be appropriate.
Many of the surveyors appointed by local shipping agents are general marine surveyors, often with a seagoing background; they are not necessarily skilled in the evaluation of the quality of fish cargoes. Masters and agents are therefore advised to check the expertise and qualifications of surveyors carefully to ensure that their technical background and experience are appropriate for the particular job.
As a general rule, a single surveyor should not be commissioned for both a cargo survey and a survey of vessel’s condition. Since the skills required for each type of assessment are very different, it is unlikely that one person would have experience in both areas at the levels of expertise required. A fish cargo surveyor should preferably have a background in food science and the inspection of food products, and ideally, some experience in assessing the quality of frozen fishery products.
Official inspectors and sampling procedures
Where official inspectors – for example, port health officers or veterinarians – are involved, the master should document the authority under which the officers visited the vessel and the name and status of each officer.
The master is also advised to record the nature and amounts of any samples taken by representatives of the owners or by officials. Such records should include the location of the samples within the hatch or deck, the authority under which the samples were taken and the destination of the samples.
If part of the sample is given to the master, he should ensure that it is fully labelled, and, if possible, that it is sealed in a container under the impress of the person taking the sample. The master should store the sample in a secure place, under conditions such that the quality of the sample will not change.
If the cargo is in store, the surveyor should take into account the manner of discharge and delivery to the store, in case these operations could have affected the quality of the product or could in themselves be responsible for any damage.