9 CONSIDERATIONS IN THE APPLICATION OF THE HACCP PRINCIPLES TO SEAFOOD PRODUCTION (Hans Henrik Huss)

The safety of seafood products varies considerably and is influenced by a number of factors such as origin of the fish, microbiological ecology of the product, handling and processing practices and preparations before consumption. Taking most of these aspects into consideration, seafood can conveniently be grouped as shown below (modified from Huss (1994))

• Molluscan shellfish

• Raw fish to be eaten without any cooking

• Fresh or frozen fish and crustaceans - to be fully cooked before consumption.

• Lightly preserved fish products i.e. NaCl <6% in water phase, pH >5.0. The prescribed storage temperature is <5°C. This group includes salted, marinated, cold smoked and gravad fish

• Fermented fish, i.e. NaCl <8% NaCl, pH changing from neutral to acid. Typically, the products are stored at ambient temperature

• Semi-preserved fish i.e. NaCl >6% in water phase, or pH < 5, preservatives (sorbate, benzoate, nitrite) may be added. The prescribed storage temperature is <10°C. This group includes salted and/or marinated fish or caviar, fermented fish (after completion of fermentation)

• Mildly heat-processed (pasteurised, cooked, hot smoked) fish products and crustaceans (including pre-cooked, breaded fillets). The prescribed storage temperature is <5°C

• Heat-processed (sterilised, packed in sealed containers)

• Dried, smoke-dried fish, heavily salted fish. Can be stored at ambient temperatures.

However, the safety of seafood products and -processing cannot be studied in isolation. A large number of hazards are related to the pre-harvest situation or the raw material handling and must be under control, when the raw material is received at the processing factory.

9.1 Hazard analysis of raw material

Most fish and shellfish are still extracted form a wild population, but aquaculture is a very fast growing food production system as outlined in Chapter 2. While there are specific safety aspects associated with wild fish caught in the high sea, the intensive husbandry in aquaculture pose new and increased risks. It is imperative that the HACCP principles are extended beyond the factory-gate and applied throughout the total food production chain from harvest to the consumers' plate.

In a general hazard analysis of the pre-harvest conditions for fish and shellfish and the procedures for handling the raw material before being received at the processing plant a number of significant hazards can be identified:

Pathogenic bacteria

Pathogenic bacteria from the aquatic or general environment may be present in low numbers in all fish and shellfish at the time of harvest (see section 5.1.1.1). This is not a significant hazard as it is unlikely that these pathogens will be there in sufficient numbers to cause disease - even if the fish are eaten raw. However, if growth and toxin production of these organisms is taking place as a result of time/temperature abuse, it is reasonably likely that these pathogens and their toxins could reach unsafe levels. For fish to be eaten raw or used as raw material in products that are not heat-treated, this situation is a significant hazard that must be controlled. High numbers of e.g. pathogenic Vibrio spp. may accumulate in bivalves, but it is unlikely that pathogenic levels will be reached (see section 5.1.1.1.).

Pathogenic bacteria from animal/human reservoir may be present in fish and shellfish harvested in contaminated waters. This is a significant hazard for fish and shellfish to be eaten raw due to the low MID (Minimum Infective Dose) for some of these organisms.

The preventive measures for these hazards are control and monitoring of harvest areas for faecal pollution (see section 11.2) and placing a limit on the time between harvest and refrigeration to prevent growth and toxin production.

Viruses

The presence of viruses in the harvest area is of particular concern in molluscan shellfish because:

• environments where molluscan shellfish grow are often subject to contamination from sewage which may contain pathogens (bacteria, viruses)

• molluscan shellfish filter and concentrate pathogens that may be present in the water

• molluscan shellfish are often consumed raw or only partially cooked.

Thus, the presence of virus is a significant hazard in molluscan shellfish and fish to be eaten raw. The preventive measure is control and monitoring of harvesting areas for faecal pollution (section 11.2).

Biotoxins

Contamination of fish and shellfish with natural toxins from the harvest area can cause serious consumer illness. The toxins accumulate in fish when they feed on marine algae, where the toxins are produced. They occur in fish from the tropical and subtropical area (ciguatera) and in shellfish worldwide (see section 5.1.5). In order to determine if ciguatera fish poisoning (CFP) is a significant hazard, some guidance can be provided by the historical occurrence of the toxin and knowledge about the safety of the reefs from which the fish has been obtained.

The preventive measures for the presence of toxins in shellfish are control and classification of shellfish harvesting areas (section 11.1). As a result, shellfish harvesting is only allowed from "safe" waters. Significant elements in this system is the requirement, that all shellfish containers bear a tag that identifies the type and quantity of shellfish, the harvester, harvest location and date of harvest.

The preventive measure for CFP is to ensure that incoming fish have not been caught in an area for which there is a CFP advisory or for which there is knowledge that CFP is a problem.

Biogenic amines

These amines are produced as a result of time/temperature abuse of certain fish species and they can cause illness in consumers. It is therefore a post-harvest hazard, but very often a pre-receiving hazard introduced during handling on board the fishing vessel or during transportation to the plant after landing.

The preventive measure is rapid chilling of fish immediately after capture. Generally, fish should be packed in ice or chilled sea water in less than 12 h after catch or - in case of large fish such as tuna - chilled to an internal temperature of 10°C or less within 6 h after capture.

Parasites

It is reasonably likely that parasites will be present in significant numbers of wild caught fish species - and certain aquaculture fish if they are fed on an unheated processing waste or by-catch fish. Thus, parasites should be considered a significant hazard and a preventive measure to eliminate parasites must be identified during processing of any particular fish products.

Chemicals

Concern for this hazard primarily focus on fish harvested from fresh water, estuaries and near shore coastal waters and on fish from aquaculture. Without proper control it would be reasonably likely to expect that unsafe levels of chemicals could be present in the fish, thus representing a significant hazard. Apart from a few acutely toxic chemicals such as mercury, most chemicals are of medium severity from a health perspective.

The preventive measure is the presence of government controlled monitoring programme (see section 11.3) and ensuring that fish have not been harvested from waters that are closed to commercial fishing. For aquaculture fish the preventive measures are full controls of chemical contamination of the environment (soil/water) surrounding the aquaculture site, control of water quality and of the feed supply. Only approved agrochemicals and veterinary drugs should be used and only according to manufacturers' instructions. Correct withdrawal times must be observed.

Table 9.1 summarizes the hazard analysis of the pre-harvest/pre-receiving situation.

One of the great problems in ensuring the safety of seafood products is that processors often have no control and no information about the history of the raw material. This is a serious weakness and every effort to overcome this problem must be carried out. The significant hazards associated with the raw material must be identified and controlled before the raw material is received at the factory. The receiving step is the first CCP in any seafood processing, and the monitoring procedures will mainly be to check documents (certificates of origin, harvester, date and location of harvesting, copies and results of government monitoring programs, etc.).

Table 9.1 Hazard analysis of pre-harvest conditions and raw material handling.

1. PP = Prerequisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.2 Hazard analysis of processing of bivalve shellfish.

1. PP = Prerequisite Programme

9.2 Molluscan shellfish

The molluscan shellfish are harvested by being raked or trawled from the bottom (oysters, mussels) or dug from the sand at low tide (clams and cockles). After harvesting, the shellfish are sorted (size), washed and packed in bags or crates or just left in a pile on deck. The shellfish may be transported and sold live to the consumer or they may be processed (shucked) raw or by use of heat. The heat applied in processing is only enough to facilitate shucking by causing the animal to relax the adductor muscle, and has no effect on the microbial contamination of the animals. The shucked meat is washed, packed and sold fresh, frozen or further processed and canned.

Most molluscs (oysters, mussels, clams, cockles) grow and are harvested in shallow, near-shore estuarine waters. Thus there is a strong possibility that the live animals may be contaminated with sewage-derived pathogens (pathogenic bacteria, viruses) as well as those from the general environment. Also biotoxins and chemicals can be present. Due to the filter feeding of molluscs, a high concentration of disease agents may be present in the animals and therefore constitutes a serious hazard. During processing further contamination with pathogens (bacteria, virus) may take place including growth of bacteria if time and temperature conditions are favourable. As most molluscs are traditionally eaten raw or very lightly cooked, this will further increase the risk. This is confirmed by the epidemiological evidence presented by Garret and Hudak-Roos (1991), who reported that 7% of all outbreaks of seafood-borne diseases (20% of all cases) in the USA in the period 1982-87 were caused by molluscan shellfish.

Although molluscan shellfish constitutes less than 0.1% of the seafood consumed in the USA, they are responsible for a great number of disease outbreaks caused by pathogenic bacteria, toxic marine algae or viruses. Available surveillance data suggests that seafood-borne diseases due to unknown aetiologies, such as unspecified hepatitis and certain Vibrio species (V. parahaemolyticus, V. vulnificus, non 01 V. cholera) represent the greatest risk for persons consuming raw molluscan shellfish (Ahmed, 1992). In England and Wales, 17 general outbreaks of gastroenteritis in 1996 and 1997 were associated with consumption of shellfish (Anon., 1998) where a total of 232 people became ill. Five outbreaks were associated with small round structured viruses (SRSV). Astrovirus, diarrhetic shellfish poisoning (DSP) and salmonellae were each associated with one outbreak. In another five outbreaks, a viral aetiology was suspected and in four outbreaks no pathogen was identified.

Viruses were also the most significant cause of shellfish-associated diseases in New York State (Lipp and Rose 1997). A total of 339 seafood-associated outbreaks were reported in the period 1980-94 and shellfish accounted for 216 (64%) outbreaks. Norwalk virus and gastrointestinal virus (small round structured virus) were the most common cause of disease. Thus a number of significant hazards can be identified as shown in Table 9.2 above:

It follows that the significant hazards to be controlled in molluscs processing are:

a. Contamination with pathogens (bacteria, viruses, biotoxins, chemicals) from the harvesting area

b. Further contamination with pathogens (bacteria, virus) during processing

c. Growth of pathogens during processing and storage

The following preventive measures can be applied to minimise the risk outlined above:

It is well known that none of these measures are 100% effective, but unfortunately no other CCP can be identified for this hazard (contamination). For this reason, molluscs to be eaten raw should be provided with a warning label to inform consumers of the risk.

Therefore, the only two critical control points to be identified and included in the HACCP plan are 1) the receiving step where it is possible to exercise control of the source of the molluscs, and 2) the labelling step, where it can be checked that the raw consumption warning is on the label. The following details could be entered in the HACCP plan for the receiving step:

A generic HACCP plan for production and processing of oysters to be consumed raw is shown in Appendix 4.

9.3 Raw fish - to be consumed raw

The hazards related to these products are primarily associated with the pre-harvest / pre-receiving situation (section 9.1). However, in the hazard analysis some of these hazards can be excluded. As already stated, contamination of raw fish with indigenous pathogenic bacteria is unlikely to be high enough to provoke disease and therefore not a significant hazard. Growth of these bacteria and of histamine producing bacteria is a potential hazard, but it is very unlikely in a product to be eaten raw. For this to happen the fish must be kept for some time at elevated temperatures and in this case also spoilage organism will grow. Since the latter will grow much faster than the pathogens the fish is likely to spoil or be unfit for raw consumption before sufficient growth of pathogens and histamine producing bacteria has taken place. The results of a general hazard analysis are shown in Table 9.3.

The significant hazards are:

a. Contamination of fish with non-indigenous bacteria, viruses, biotoxins or environmental chemical contaminants (heavy metals, pesticides, drugs in aquaculture)

b. Presence of parasites.

The following preventive measures can be applied:

While the preventive measure for control of parasites is 100% effective, this is not the case for control of the pre-harvest contamination of fish with pathogenic organisms or compounds. There are serious weaknesses in a monitoring program as outlined in Chapter 11, and no effective CCP can be identified for the control of ciguatera.

Only two CCPs are identified in the processing of raw fish to be eaten raw:

• the receiving step

• the freezing step

9.4 Fresh/frozen fish and crustaceans - to be fully cooked before consumption

The hazard analysis of these products is fairly straightforward and uncomplicated. The animals are in most cases caught in the sea or freshwater, handled and processed without any use of additives or chemical preservatives and finally distributed with chilling or freezing as the only means of preservation.

The epidemiological evidence has shown that the presence of histamine or biotoxins accounts for nearly 80% of all disease outbreaks caused by "fish". Low levels of pathogenic bacteria and viruses may be present on raw fish as part of the natural flora and/or as a result of contamination during handling and processing. As the product will be cooked before consumption, it is very unlikely that this low level of pathogens will cause any disease. Even if any growth has taken place in the raw fish to be cooked, it is unlikely to produce any disease. Pathogenic bacteria and viruses are therefore not significant hazards, which need to be controlled.

In contrast the biotoxin (ciguatoxin and tetrodotoxin) are heat stable and cooking the fish before consumption is not likely to eliminate this hazard. In areas where this hazard is likely to occur (see section 5.1.5) it must be noted as a significant hazard.

Similarly the biogenic amines (histamine) are resistant to heat, and if present in the raw fish it is likely to cause disease. Production of histamine in raw fish is therefore a significant hazard that must be controlled (see also section 5.1.2).

Parasites are common in fish, but normal household cooking will kill the parasites, and their possible presence is therefore not a significant hazard.

Chemical contamination of fish is unlikely and not a significant hazard except for aquaculture fish and fish from coastal areas subject to industrial pollution (see section 5.2).

Table 9.3 Hazard analysis of raw fish to be consumed raw.

1. PP = Pre-requisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.4 Hazard analysis of fresh/frozen fish and crustaceans to be cooked before consumption.

1. PP = Pre-requisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.4 summarize the hazard analysis for this product. Thus, the significant safety hazards are:

• Presence of biotoxins. This hazard only applies to fish from warm waters with a history of causing ciguatera (Ciguatera fish poisoning, CFP) and to puffer fish

• Formation of histamine. This hazard only applies to scombroid fishes (see section 5.1.2)

• Presence of chemicals. This hazard only applies to fish from aquaculture or coastal areas.

For all other fish (~ the large majority of marine fish) there are no safety hazards and no HACCP plan is required, only a Hazard Analysis Worksheet needs to be elaborated.

The preventive measures that can be applied to the significant hazards are:

• Sorting of the catch to exclude puffer fish. Making sure that the fish have not been caught in an area for which there is a CFP advisory or for which there is knowledge of a CFP-problem. It is clear that the latter preventive measure is not 100% effective, but no other means are available

• Rapid chilling of fish immediately after catch to temperatures <10°C is the most important element in any strategy for preventing the formation of histamine. Further chilling towards the freezing point is desirable to prevent long-term low-temperature development of histamine. Control of temperature is part of the prerequisite programme

• The preventive measure for chemical contamination of fish is to compare information on capture area with government ban on fishing.

Based on the above, the only CCP for raw fish to be cooked before consumption is the receiving step [possible histamine formation during processing and storage of scombroid fish is taken care of by the pre-requisite programme]. The following details can be entered in the HACCP plan:

9.5 Lightly-preserved fish products

This group includes fish products with low salt content (Water Phase Salt (WPS) <6%) and low acid content (pH >5.0). Preservatives (sorbate, benzoate, NO₂, smoke) may or may not bee added. The products may be prepared from raw or cooked raw material, but are normally consumed without any prior heating. Product examples are salted, marinated, cold smoked or gravad fish. These products have a limited shelf life and are typically stored at temperature £ 5°C. The presence in these products of low numbers of pathogenic bacteria normally found in the aquatic and the general environment (Clostridiums botulinum, pathogenic Vibrio sp., Listeria monocytogenes) is a potential hazard. Due to their low numbers, the mere presence is not a significant hazard. However, if these organisms are allowed to grow to high numbers, they are very likely to cause a serious disease, and are therefore representing a significant hazard. It should be remembered, that growth and toxin production can take place in the raw material as well as in the final product.

Contaminations of products during processing with viruses and non-indigenous pathogenic bacteria as well as possible growth of the latter are also potential hazards. However, these hazards are prevented by the prerequisite programme and therefore not likely to occur.

The presence of biotoxins (Ciguatera Fish Poison, CFP) is a potential hazard if the raw material is a fish specie with a history of causing CFP and originating in an area where CFP is known to occur.

Production of biogenic amines is a significant hazard in all products based on scombroid fish or all fish containing large amounts of free histidine in the flesh. The production requires growth of histamine-decarboxylating bacteria. A number of different bacteria are able to produce histamine at various conditions (as discussed in section 5.1.2). It should be remembered that biogenic amines may be produced in the raw material as well as in final products.

Parasites are common in many fish species in all parts of the world, and the processing conditions and preservative parameters for lightly preserved fish products are not sufficient to kill the parasites. Thus, a "processing for safety" step must be included in the process of this type of products to control this significant hazard.

Chemical contamination of raw material is a potential hazard if it originates in aquaculture or certain coastal fisheries. Only if this is the case, should chemical contamination be regarded as a significant hazard.

The hazard analysis is summarized in Table 9.5. The significant hazards are the result of:

a. Growth of pathogenic bacteria from the aquatic or the general environment
b. Production of biogenic amines (scombroid fish)
c. Presence of parasites
d. Chemical contamination (depending on geographical area).

The following preventive measures can be applied:

Based on the considerations above, the following CCPs can be identified: Receiving step, salting step and freezing step. The following details can be entered in the HACCP plan:

9.6 Fermented fish

Traditionally the term "fermented fish" covers both enzyme hydrolysed and microbial fermented fish products. However, a clear distinction should be made between these products. Thus, Paludan-Müller (2002) suggests to define fermented fish as "products which contain a carbohydrate source and in which the level of salt is less than 8% water phase salt (WPS)". This level of salt (£8%) allows the fermentative growth of lactic acid bacteria and a concomitant decrease in pH to <4.5. In contrast enzyme hydrolysed fish has a WPS >8% and a final pH between 5-7. A large number of different fermented fish products are found in South-East Asia. The products are traditionally stored at ambient temperatures and consumed without any cooking. Fermented fish products have been associated with a number of outbreaks of food-borne diseases such as botulism, trematodiosis, salmonellosis and vibriosis.

The natural presence of pathogenic bacteria from the aquatic and general environment is not considered a significant hazard in this product due to the low numbers. However, conditions for growth of some of these organisms (C. botulinum type A and B, Listeria monocytogenes, Vibrio sp.) are good until the pH decreases to near 4.5. This takes about 1-2 days at 30°C in a natural fermentation. Rapid and adequate acidification is therefore the preventive measure for this significant hazard. For complete safety, temperatures during fermentation should be kept at <10°C until final pH has been reached.

Contamination of fermented fish products with pathogenic bacteria from the animal/human reservoir and with pathogenic virus are potential hazards, which will be controlled by the prerequisite programme.

Most fermented fish products are based on freshwater fish as raw material. However, if marine fish are used, the presence of biotoxin (CFP) should be considered a potential hazard as discussed in section 9.1.

Formation of biogenic amines (histamine) is a health hazard primarily related to marine, scombroid fish species and is not a potential hazard when freshwater fish are used as raw material.

Parasites, particularly trematodes are very common in fish used as raw material for fermented fish. As there is no killing step for these parasites in the normal processing they are very likely to cause disease and must be regarded as a significant hazard. The preventive measures are food safety education and to bring about changes in the traditional consumption practices of eating non-cooked fermented fish. Until then fermented fish to be eaten without any cooking must have a freezing step included (see section 5.1.4). The concern for chemical hazards are related to the raw material and described in section 9.1.

Table 9.5 Hazard analysis of lightly preserved fish products.

1. PP = Prerequisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.6 Hazard analysis of fermented fish.

1. PP = Prerequisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

The hazard analysis for fermented fish products is summarized in Table 9.6. The CCPs in production of fermented fish are:

9.7 Semi-preserved fish

These are fish products with >6% water phase salt (WPS) or a pH <5.0. Preservatives (sorbate, benzoate, nitrate) may or may not be added. These products require chill storage (< 10°C) and may have a shelf life of 6 months or more. Normally, there is no heat-treatment applied neither during processing nor in the preparation before consumption. Traditional production often includes a long ripening period (several months) of the raw material before final processing. Product examples are salted and marinated fish, fermented fish and caviar products.

There is epidemiological evidence that this type of products has been the cause of illness related to the presence of bacterial toxins (botulism), parasites, biotoxins and histamine.

The presence of low numbers of pathogenic bacteria normally found in the environment is not a significant hazard in these products (not likely to cause disease). Contamination with non-indigenous pathogens (bacteria and viruses) is a potential hazard to be prevented by the prerequisite programme.

Growth and possible toxin production of pathogenic bacteria is not possible in these products if correctly processed and storage temperature is kept at £10°C. As for lightly preserved fish products it must be pointed out that growth and toxin production may take place in the raw material. Bacterial toxins, incl. botulinum toxins are very stable at high salt and low pH (Huss and Rye Petersen, 1980). Any toxin present or preformed in the raw material will be carried over to the final product, and this hazard can only be controlled by having full control over the complete handling and processing steps from harvesting to consumption.

Biotoxins (ciguatera) is a potential hazard only if the raw material used is a fish specie with a history of causing CFP and originating in an area where CFP is known to occur. This is not very likely to happen, and therefore biotoxins are not a significant hazard for this product.

Production of biogenic amines may take place both in the raw material and in the final product. It is a significant hazard as it is very likely to occur in scombroid fish if there is a loss of control.

Parasites are very common in fish species used as raw material for semi-preserved products. This hazard is therefore significant (likely to occur) and must be prevented.

Chemical contamination of raw material is a potential hazard if it originates from aquaculture or certain coastal fisheries. Table 9.7 summarizes the hazard analysis of these products. The CCPs in production of semi-preserved fish products are:

Monitoring procedures, corrective action programme and verification procedures must be set up and records kept of all actions

9.8 Mildly heat-processed fish products

A number of fish products receive a heat treatment during processing. Examples are: pasteurised or cooked and breaded fish fillets, cooked shrimp and crabmeat, cook-chill products and hot smoked fish. After the heat-treatment the various products may pass through further processing steps before being packed and stored/distributed as chilled or frozen products. Some of these products may receive additional heat treatment before consumption (cooked and breaded fillets, cook-chill products) or they may be eaten without further treatment (hot smoked fish, cooked shrimp). Thus, some of these products are ready-to-eat and extremely sensitive to contamination after the heat treatment.

To further illustrate the safety aspects, there is ample epidemiological evidence that this type of product has been the cause of food poisoning due to growth of coagulase-positive Staphylococcus aureus and enteropathogenic organisms among the Enterobacteriaceae and Vibrionaceae. Marine crustaceans, usually shrimp, crab or dishes made from them, accounted for 25 outbreaks of food-borne diseases reported in the USA during the period 1977-84 (Bryan, 1988).

In the application of the HACCP system to these types of products, the heat-treatment is a very critical processing step. Hazards identified before this step may or may not be eliminated depending on the degree of heat being applied. Most criteria for heat-treatments have been laid down as a consequence of economical and technological considerations and not for hygienic or public health reasons. Increased safety will be obtained if the cooking/heating procedures could be designed to eliminate vegetative cells of pathogens and spores of the most sensitive species. Generally, a reduction of six orders of magnitude (six logarithms) in the level of contamination is recommended. This performance criterion is the so-called 6D process ("D" stands for "decimal reduction") as described in section 13.2.

Listeria monocytogenes is normally used as a target organism for measuring the heat treatment and is regarded as the most heat-resistant food-borne pathogen that does not form spores.

Most products in this group are depending entirely on the heating process and chilled storage for safety and shelf life as they do not contain any bacteria controlling ingredients. It is very likely that pathogens will cause disease if these factors are out of control. Pathogen survival during the cooking/heating procedure and pathogen growth during storage are significant hazards that must be included in the HACCP plan. In contrast, it is very unlikely that viruses, parasites and histamine producing bacteria will survive the heat treatment.

Recontamination of products after the heat-treatment and before packaging can also cause consumer illness. In many productions this hazard will be controlled by the prerequisite programme. In others, where e.g. the recontamination is caused by faulty container sealing or incorrect hot-filling procedures, recontamination is a significant hazard that needs to be included in the HACCP plan.

Considerations to the possible presence of biotoxin and chemical contamination should be as outlined in section 9.1. Table 9.8 summarizes the hazard analysis of these products.

In a simple production (e.g. cooked shrimp vacuum-packed in plastic bags) the significant hazards are:

a. Survival of pathogens
b. Recontamination after cooking
c. Growth of pathogens
d. Raw material quality (chemical hazards).

The CCPs during production will be:

Recontamination and growth of pathogens will be taken care of by the prerequisite programme. The critical limits for the cooking step (time/temperature conditions) should be set at a point that if not met the safety of the product may be questionable. If a more restrictive limit is set, the result will be a loss of product.

Table 9.7 Hazard analysis of semi-preserved fish.

1. PP = Prerequisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.8 Hazard analysis of mildly heat-processed fish.

1. PP = Pre-requisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

9.9 Heat-sterilized fish products packed in sealed containers (canned fish)

The basis for canning is the use of thermal processing to achieve sterility of the final product. The containers are distributed at ambient temperatures and often stored for months even years under these conditions. The contents of the cans are normally eaten without any heating immediately before consumption.

Canned fish has been the cause of outbreaks of botulism and cases of histamine and staphylococcal enterotoxin poisoning (Ababouch, 2002). The general hazard analysis is shown in Table 9.9.

The significant hazards related to this type of products are:

• Quality of raw material (biotoxins, chemicals)
• Survival of pathogens (C. botulinum) during heat processing
• Presence of heat-stable toxins (biotoxins, histamine, S. aureus ET)

• Recontamination of product after heat processing (faulty containers, poor sealing, contaminated cooling water, faulty container handling).

The CCPs for these hazards are:

Additional verification procedures are common practice and in some cases a legal requirement (EC 1991). This includes checks carried out at random to ensure that products have undergone appropriate heat treatment. This requirement involves taking samples of the final product for:

- incubation tests. Incubation of samples must be carried out at 37°C for seven days or at 35°C for ten days or any other equivalent combination

- microbiological examination of contents of containers in the establishments laboratory or in any other approved laboratory.

9.10 Dried, smoke-dried, heavily-salted fish

These are products with a very high salt content (>10% WPS) and/or a very low water activity (a_w £ 0.85). Dried or salted fish are usually considered stable at high temperatures and therefore stored and distributed at ambient temperatures.

No growth of pathogens is possible in these products if correctly processed, not even at ambient temperatures. The most salt-tolerant pathogenic organism is Staphylococcus aureus (which can grow at a_w ³ 0.83 and produce toxin at Aw ³ 0.85, see also section 5.1.1.2), and this organism should therefore be considered as target pathogen for drying.

A critical phase in processing is the time until salt has penetrated and the WPS reaches 10% or the a_w is below 0.85 in the thickest part of the fish. For this reason larger fish (>15 cm in length) should be eviscerated prior to processing.

Contamination of dried or salted fish with enteropathogenic bacteria and viruses is a potential hazard, which will be prevented by the prerequisite programme.

The presence of toxic fish and chemical contamination of raw material are potential hazards as discussed in section 9.1.

The possible presence of parasites is not a significant hazard in these products. It is very unlikely they will cause a disease due to the rapid killing of the parasites in an environment with very high salt content (see section 5.1.4).

Table 9.9 Hazard analysis of heat sterilised products packed in sealed containers (canned fish).

1. PP = Prerequisite Program me
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

Table 9.10 Hazard analysis of dried, smoke-dried or heavily salted fish.

1. PP = Pre-requisite Programme
2. depending on fish/bivalve shellfish species, geographical position and season, the likely occurrence may be high or low

When scombroid fish are used as raw material, formation of histamine is a significant hazard. Histamine may be formed in the raw material before processing (see section 9.1.) but also in the final product as some halophilic bacteria are able to produce this compound (Kimma et al., 2001). However, there is some uncertainty if this is a theoretical risk only. There are no reported cases of histamine poisoning from these products and there are no experimental data to demonstrate the possible risk.

The CCPs in the production of dried or salted fish are:

9.11 Seafood risk categories

In ranking seafood into risk categories, the method of NACMCF (1992) with some modifications has been applied. The following six hazard characteristics and risk factors have been considered:

1. No terminal heat treatment. Apart from raw fish to be eaten cooked or fried, all other fish products are ready-to-eat

2. The safety record. Is there any evidence, that this particular product has been associated with food borne disease many times - or with very serious diseases? With reference to tables in section 4.1 it can be stated, that the safety record is poor for:

• molluscan shellfish and fish to be eaten raw due to the presence of (accumulated) biological hazards (viruses, pathogenic bacteria, parasites, biotoxins)

• molluscan shellfish, tropical reef fish and scombroid fish to be cooked before consumption due to the presence of heat stable aquatic toxins or scombrotoxin

• presence of heat stable biogenic amines in canned sterilised products and few outbreaks of botulism caused by the same type of product

• some fermented fish; e.g. salted fish from the Middle East or products from Alaska

3. The production/processing does not include a Critical Control Point for at least one identified hazard. This situation applies to the:

• accumulation of biological hazards in shellfish (see section 5.13)

• presence of biotoxins (ciguatera) in fish from tropical reefs (see section 5.13).

4. The product is subject to potentially harmful contamination or recontamination after processing and before packaging. All raw fish and fish product, which has not been subject to any bactericidal treatment, are likely to harbour pathogenic organisms as part of their natural flora (see section 5.1.1.). Potentially harmful recontamination is possible and reasonably likely to occur for products being mildly heat-treated before being placed in the final container (cooked shrimp, hot smoked fish). However, also the risk associated with lightly preserved fish and fish and shellfish to be eaten raw may increase due to this factor (e.g. contamination of cold smoked fish with L. monocytogenes).

5. Products with a potential for abusive handling. This hazard refers mainly to handling and storing the fish product at abuse (elevated) temperatures. With the exception of sterilised, canned or fully preserved products, there is a potential for this hazard for all other types of fish products. However, this is not likely to occur for fish to be consumed raw, as spoilage will be very fast at elevated temperatures

6. Growth of pathogens. The growth of pathogens, particularly in ready-to-eat products is a serious hazard. Two potential hazards of this nature are known and likely to occur: the possible growth of L. monocytogenes in lightly preserved fish products and the growth of C. botulinum in some types of fermented seafoods. Growth of other pathogens in preserved or heat-processed products is possible only if the preserving parameters are not applied as specified (see text) and other potential hazards are in fact occurring (temperature abuse, recontamination of heat processed fish). Spoilage bacteria will grow in all types of fish products (except sterilised products) and in most cases they will grow faster than any pathogen. This is particularly the case in raw, unprocessed or unpreserved fish, and for this reason growth of pathogens it is not considered an additional hazard likely to occur and influence the safety of this product.

The above considerations above are summarized in Tables 9.11 and 9.12. The various seafoods are assigned to a risk category in terms of health hazards by using a "+" (plus) to indicate a potential risk related to the hazard characteristics. The number of plusses will then determinate the risk category of the seafood concerned.

Table 9.11 Risk categories for fresh seafood products (modified after Huss et al., 2000).

1. High risk products have 4 or more plusses. Medium risk products have 3 plusses. Low risk products have 2 plusses or less.

Table 9.12 Risk categories for processed seafood products (modified after Huss et al., 2000).

1. High risk products have 4 or more plusses. Medium risk products have 3 plusses. Low risk products have 2 plusses or les

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