118 Questions
Who is responsible for the identification, classification and monitoring of areas related to bivalve molluscs?
Competent authorities
What is used as an indicator for the possibility of faecal contamination in bivalve molluscs?
Escherichia coli/faecal coliforms or total coliforms
What is the purpose of relaying or depuration in bivalve molluscs?
To reduce microbiological contamination
When should a growing area be closed for harvesting bivalve molluscs?
When biotoxins are found in hazardous amounts
What should be avoided when bivalve molluscs need to undergo relaying or depuration?
Stress and excessive shocks
What is required for controlling pathogenic Vibrio spp. in bivalve molluscs?
Refer to the Annex on the Control Measures for Vibrio parahaemolyticus and Vibrio vulnificus
What is the purpose of toxicological investigation in bivalve molluscs?
To ensure the bivalve mollusc meat is free from hazardous amounts of biotoxins
Why should harmful chemical substances be absent or present in limited amounts in bivalve molluscs?
To prevent exceeding the permissible daily intake
What should growing areas be routinely monitored for?
Changes in water quality and bivalve mollusc quality
Why is it recommended to have a programme to monitor growing areas for certain species of plankton?
To detect biotoxins in bivalve molluscs
What should be considered when determining the public health suitability of bivalve mollusc classified growing areas?
All of the above
What should be monitored in growing water and/or molluscan flesh according to the code of practice?
E. coli/faecal coliforms or total coliforms
What should be done if faecal contamination exceeds a certain threshold level?
Relay or depurate for a time approved by the official agency
Why are E. coli/faecal coliforms or total coliforms used as indicators?
To detect faecal contamination in bivalve molluscs
What should be done to prevent harvesting of bivalve molluscs from substandard areas?
Patrol substandard areas to prevent harvesting
What should be done to prevent harmful chemical substances in bivalve molluscs?
Monitor for harmful chemical substances
What should be considered when classifying or reclassifying growing areas?
All of the above
What should be done if the growing area no longer meets the classification criteria?
Reclassify or close the area immediately
What is the main reason why bivalve molluscs should be able to function again during depuration, relaying or conditioning?
To allow them to recover and thrive in a clean environment
What are the five types of important hazards that may occur in the growing environment of bivalve molluscs?
Enteric bacterial pathogens, enteric viral pathogens, naturally occurring bacterial pathogens, biotoxins, and chemical contaminants
Why should surveys of the growing area, shoreline, and land catchment be conducted?
To identify sources of pollution
What should be considered when interpreting growing area data?
Variations that may affect the level of pollution during the most unfavourable hydrographic and climatic conditions
What should be used as a guide to acceptable levels of pollution in growing areas?
Standards of the Food and Agriculture Organization of the United Nations (FAO) and World Health Organization (WHO)
What should be done if the limits of any biological or chemical hazard set in the end-product specification are exceeded?
Appropriate measures should be taken under the responsibility of the official agency having jurisdiction
What should be clearly defined by the official agency having jurisdiction?
The classification of growing areas
What is the primary focus of shellfish sanitation programmes?
Using indicator organisms for contamination presence
What is the purpose of classifying growing areas?
To ensure that bivalve molluscs are suitable for human consumption
When is it appropriate to monitor for specific pathogens in shellfish?
After a shellfish-borne outbreak
What is the purpose of phytoplankton monitoring in shellfish sanitation?
To optimize programme management and resources
Why should the ability of bivalve molluscs to accumulate toxic chemicals be considered?
To ensure that bivalve molluscs are suitable for human consumption
What should be re-evaluated on a regular basis to determine any changes in their impact on the growing area?
Known pollution sources
What is assumed when using indicator shellfish species?
The absence of toxicity in other species
What should happen when acceptable levels of biotoxins are exceeded in edible portions of bivalve mollusc meats?
The affected areas should be immediately closed and patrolled
What should be considered when establishing a sampling programme over space and time?
The location and number of sampling sites
Why is spatial representational sampling important?
To cover the risks of rapid rises in shellfish toxicity
What factors should be used to select sampling stations for benthic and suspended culture?
All of the above
What should be demonstrated before defining a particular shellfish species as an indicator for a growing area?
The implication that the absence of toxicity in the indicated species implies the absence of toxicity in other species
Why is it important to recognize seasonal variability in the risk of blooms of toxic algae?
To draw up monitoring schedules
What is the primary purpose of routine sampling for microalgae?
To take an integrated sample from the water column
What is the recommended approach when a toxic event is in progress or developing?
Consider targeted, depth-specific sampling
What factors should influence the decision on the frequency of sampling?
Seasonality, accessibility, historical baseline information, and environmental factors
What should be the determining factor for the shellfish sample size?
The number of shellfish in the sample
What is the purpose of a 'marine biotoxin action plan'?
To describe the sampling frequency and factors that may lead to its change
What is the recommended approach for shellfish grown in suspension?
Take an integrated sample composed of shellfish from the top, middle, and bottom of the lines
Why should sampling frequency be based on risk evaluation?
To ensure that toxicity and harvesting are taken into account
What is the purpose of monitoring for chemical contaminants?
To provide confidence that identified sources of contamination are not affecting the shellfish
What should be cleaned and disinfected before being used for harvesting bivalve molluscs?
Dredges and other harvesting equipment
What is the importance of sufficient sample size?
To allow for the tests to be carried out and to account for variability among individual shellfish
What is the primary purpose of requiring bivalve molluscs to be held above the floor level and drained?
To prevent contamination from polluted water
What should be used to wash bivalve molluscs soon after harvesting?
Clean seawater or potable water
Why should the interval between harvesting and immersion in water for relaying, storage, or depuration be kept as short as possible?
To minimize the risk of temperature fluctuations
What is a potential hazard during relaying operations?
Microbiological contamination
What should be in place to prevent cross-contamination and commingling during relaying operations?
Adequate control systems
What should be avoided during the handling and transportation of bivalve molluscs?
All of the above
What is the purpose of maintaining documentation for harvesting and transportation activities?
To ensure compliance with regulations
What should be used to re-immersize bivalve molluscs after harvesting if necessary?
Clean seawater
Why should overboard discharge of waste, including human faecal material, not occur from harvest vessels around shellfish growing areas?
To prevent contamination of the water
What should be taken to protect bivalve molluscs from being contaminated during harvesting and transportation?
Suitable precautions
What determines the holding time and minimum temperature in the accepted area prior to harvest?
The degree of contamination before relaying, water temperature, and local geographic conditions
What should be monitored while relaying sites are being used for relaying?
The presence of environmental pathogens such as Vibrio bacteria and biotoxins
Why should bivalve molluscs be laid out at a certain density during relaying?
To allow them to open and undergo natural depuration
What is the purpose of depuration in bivalve molluscs?
To reduce the number of pathogenic microorganisms to safe levels
What is the primary requirement for seawater used in tanks, floats, natural sites, or rafts for storing bivalve molluscs?
It should be of adequate salinity and physical water quality
What should be removed prior to the depuration process, if possible?
Dead or damaged bivalve molluscs
Why should dead or damaged bivalve molluscs be removed before storage?
To prevent contamination and deterioration
What should be washed with clean seawater before the depuration process, if necessary?
The surfaces of the shells
What is the purpose of laying out bivalve molluscs at a certain density during storage?
To permit them to open and function normally
What should be considered when determining the length of the depuration period?
The water temperature, physical water quality parameters, degree of contamination, and bivalve mollusc species
Why should tanks be placed in a well-ventilated building or away from direct sunlight?
To prevent weakness in bivalve molluscs due to high temperatures
What should be used to assess depuration parameters?
Microbiological investigation of both process water and bivalve mollusc meat
Why should water used in depuration tanks be changed or treated?
To prevent re-contamination of the bivalve molluscs
What should be removed from the shells of bivalve molluscs during washing?
Mud and soft commensal organisms
Why should bivalve molluscs be handled carefully?
To prevent mechanical damage and stress
What should be taken into account when depurating bivalve molluscs?
The presence of viruses and Vibrio spp., which are more persistent during depuration
What is the purpose of declumping and debyssing bivalve molluscs?
To separate clumped bivalve molluscs
What should be ensured during packaging of bivalve molluscs?
Prevention of contamination, deterioration, and growth of microorganisms
What should be used to minimize the risk of damage to bivalve mollusc shells?
Equipment designed for minimizing damage
Why should tanks be drained, cleaned, and disinfected at suitable intervals?
To maintain clean seawater quality
What should be done to bivalve molluscs after removal from the depuration system?
They should be washed with running potable water or clean seawater and handled in the same manner as living bivalve molluscs taken directly from a non-polluted area.
What should be avoided when laying out bivalve molluscs for depuration?
Laying them out at a high density to promote depuration.
What type of materials should be used to construct equipment in contact with water during depuration?
Non-porous and non-toxic materials.
What should be done to tanks after each use?
They should be cleaned and disinfected at suitable intervals.
What should be maintained for depuration activities?
Appropriate documentation.
What is the purpose of conditioning bivalve molluscs?
To remove mud, sand, and slime.
Why should bivalve molluscs with broken shells or that are otherwise unwholesome be removed?
To prevent contamination of other bivalve molluscs.
What should be done before removing bivalve molluscs from the depuration system?
The water should be drained from the system to avoid re-suspension and re-ingestion.
Why should distribution centres and establishments that prepare live bivalve molluscs maintain the same hygiene standards?
To ensure the quality and safety of the bivalve molluscs.
What should be avoided when handling bivalve molluscs in a distribution centre?
Stress and excessive shocks to bivalve molluscs.
What is the primary concern during the storage of live bivalve molluscs?
Preventing contamination with microorganisms
What should be inspected immediately before use to ensure they are in a satisfactory condition?
Packaging materials
What should be avoided when packaging live bivalve molluscs?
Contaminating the packaging material
What should be included on the label of packaged live bivalve molluscs?
The date of packaging
What should be done to the packaging material after washing?
It should be well drained before filling
What should be avoided during the distribution of live bivalve molluscs?
Temperature fluctuations during distribution
What is the purpose of conveying storage instructions on the packaging material or label?
To provide instructions to the consumer after retail purchase
What should be kept in a clean and sanitary manner during storage?
The packaging material
What should be done to prevent microbiological contamination during storage?
Avoid direct contact with the floor
What should be done to the post-harvest treated product?
It should be packed and chilled or frozen as soon as possible
What is the primary purpose of processing bivalve molluscs to reduce or limit target organisms?
To reduce the risk of microbiological contamination
What should be maintained during the distribution of bivalve molluscs to control microbial growth?
A consistent temperature
What is a potential hazard associated with the shucking of bivalve molluscs?
Physical contamination
What should be avoided when transporting bivalve molluscs?
Transporting with other products that might contaminate them
What should be done to minimize cuts and tears in the flesh during shucking?
Examine the product carefully
What should be done to eliminate mud, detritus, and sand from the shucking tables?
Take care to eliminate excess mud, detritus, and sand
What is the primary purpose of heat shocking in bivalve molluscs?
To remove shells from bivalve molluscs
What should be considered when developing a heat treatment process schedule?
The species and size of bivalve molluscs, time of exposure to heat, internal bivalve molluscs temperature, and other factors
What should be maintained for a period of at least one year?
Records of relaying and depuration
What should be done to reduce the microbiological level of shucked molluscs?
Rinse or wash the product to eliminate mud, sand, and detritus
What should be included in the documentation accompanying the transportation of live bivalve molluscs?
The gatherer's identity and signature
What should be validated scientifically before implementing a treatment to reduce or limit pathogens in bivalve molluscs?
The effectiveness of the treatment
What should be monitored to ensure that the product does not undergo unacceptable textural changes during processing?
The control treatments, such as heat and pressure
What should be inspected before heat treatment to ensure they are alive and not badly damaged?
The bivalve molluscs
What should be done to the heat-shocked bivalve molluscs within two hours of heat treatment?
They should be cooled to 7 °C or below
What should be maintained during transportation, storage, and distribution?
A temperature of 7 °C or below
What should be examined for objectionable matter before packaging?
The bivalve molluscs
What should be included in the lot number to facilitate traceability?
The number of the establishment that distributes the product
What should be developed by each establishment that heat shucks bivalve molluscs?
A heat shuck process schedule
What should be washed with pressurized potable water or clean seawater before heat treatment?
The bivalve molluscs
Study Notes
Identification, Classification, and Monitoring of Growing Areas
- Identification, classification, and monitoring of growing areas is a responsibility of the competent authorities in cooperation with fishers and primary producers.
- Escherichia coli/faecal coliforms or total coliforms may be used as an indicator for the possibility of faecal contamination.
Classification of Growing Areas
- Surveys of the growing area, shoreline, and land catchment should be conducted to determine sources of both domestic and industrial pollution.
- Sources of pollution may include municipal sewage outputs, industrial outputs, mine wastes, geophysical contaminants, domestic animal holding pens, nuclear power plants, refineries, or other sources.
- The need to reschedule hygiene surveys will be determined by population shifts and changes in agricultural and industrial activities in the coastal area.
- Re-surveys should be conducted at an acceptable frequency, and known pollution sources should be re-evaluated regularly to determine any changes in their impact on the growing area.
Monitoring of Growing Areas
- Growing areas should be routinely monitored for changes in water quality and/or bivalve mollusc quality.
- Substandard areas should be patrolled to prevent harvesting for purposes other than that established by the official agency.
- Biotoxins in bivalve molluscs can be caused by plankton containing toxins.
- Harmful chemical substances within bivalve molluscs should not be present in amounts that exceed the permissible daily intake.
Control of Harmful Substances
- Control of viruses, refer to the Annex on the Control of Hepatitis A Virus (HAV) and Norovirus (NoV) in Bivalve Molluscs (Annex I) to the Guidelines on the Application of the General Principles of Food Hygiene to the Control of Viruses in Food (CXG 79-2012).
- Control of pathogenic Vibrio spp., refer to the Annex on the Control Measures for Vibrio parahaemolyticus and Vibrio vulnificus in Bivalve Molluscs to the Guidelines on the Application of the General Principles of Food Hygiene to the Control of Pathogenic Vibrio Species in Seafood (CXG 73-2010).
Harvesting and Transportation of Live Bivalve Molluscs
- Harvesting and transportation of live bivalve molluscs should be done in a way that prevents contamination.
- Dredges and other harvesting equipment, decks, holds, and containers should be cleaned and, if applicable, disinfected (sanitized) before being used for bivalve molluscs from an unpolluted area.
Potential Hazards and Defects
- Potential hazards: microbiological contamination, biotoxins, chemical contamination
- Potential defects: physical damage, chemical contaminants### Classification and Monitoring of Growing Areas
- Relaying areas are subject to the same requirements as growing areas for classification and monitoring.
- Relaying aims to reduce biological contaminants in bivalve molluscs to acceptable levels for human consumption.
- Bivalve molluscs for relaying must be harvested from areas designated by the official agency.
Relay Operations
- Relay operations should be strictly supervised by the official agency to prevent contamination and cross-contamination.
- Boundaries of relaying areas should be clearly identified and separated from adjacent waters.
- Control systems should be in place to prevent cross-contamination and commingling.
Depuration
- Depuration is intended to reduce pathogenic microorganisms in bivalve molluscs to acceptable levels for human consumption.
- Bivalve molluscs for depuration must be harvested from areas designated by the official agency.
- Depuration alone is not suitable for heavily contaminated areas or areas with specific contaminants.
Depuration Process
- Bivalve molluscs should be laid out at a density that allows them to open and undergo natural depuration.
- The depuration process should be monitored to ensure adequate reduction of contaminants.
- Water used in depuration tanks should be changed continuously or treated properly.
Reception of Bivalve Molluscs
- Potential hazards: microbiological, chemical, and physical contamination.
- Potential defects: viable parasites, physical damage, foreign matter, and dead or dying bivalve molluscs.
- Technical guidance: avoid stress and excessive shocks to bivalve molluscs, and only accept bivalve molluscs that meet the end-product specification.
Conditioning and Storage of Bivalve Molluscs
- Potential hazards: microbiological contamination, chemical contamination, and biotoxins.
- Potential defects: physical damage, foreign matter, and dead or dying bivalve molluscs.
- Technical guidance: use clean seawater, maintain adequate salinity and physical water quality, and avoid contamination and deterioration.
Washing, Declumping, Debyssing, and Grading
- Potential hazards: microbiological contamination, chemical and physical contamination.
- Potential defects: mechanical damage.
- Technical guidance: handle bivalve molluscs carefully, minimize handlings, and avoid excessive shocks.
Packaging and Labelling
- Potential hazards: microbiological contamination, physical contamination, and chemical contamination.
- Potential defects: incorrect labelling, presence of damaged or dead bivalve molluscs, and foreign matter.
- Technical guidance: use appropriate packaging material, avoid contamination, and ensure labels are clear and comply with labelling laws.
Storage of Bivalve Molluscs
- Potential hazards: microbiological contamination, chemical and physical contamination.
- Potential defects: physical damage.
- Technical guidance: store bivalve molluscs under conditions that prevent contamination and proliferation of microorganisms.
Distribution/Transportation
- Potential hazards: microbiological contamination.
- Potential defects: physical damage.
- Technical guidance: maintain temperature control, avoid damage to packaging, and ensure distribution is in the sequence of lot numbers.
Processing to Reduce or Limit Target Organisms
-
Potential hazards: microbiological contamination.
-
Potential defects: coagulation of meat, defective meat texture, and hydrostatic medium forced into the flesh.
-
Technical guidance: validate scientifically any treatment developed to eliminate or reduce pathogens, and monitor treatment parameters closely to ensure product quality.### Shucking and Washing of Shellfish
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Physical removal of shellfish meat from the shell can expose the product to dirt, mud, and detritus, which must be removed before further processing through washing or other means.
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Potential hazards: physical contamination, microbiological contamination
-
Potential defects: cuts and tears in the flesh, presence of sand and mud
Technical Guidance for Shucking and Washing
- Care should be taken to eliminate excess mud, detritus, and sand from the shucking tables.
- The product should be examined to ensure that cuts and tears are minimized.
- Shucked molluscs should be rinsed or washed to eliminate mud, sand, and detritus and to reduce the microbiological level of the products.
Heat Shocking of Bivalve Molluscs
- Heat shocking is a method to remove shells from the bivalve molluscs.
- Potential hazards: physical contamination
- Potential defects: unlikely
Technical Guidance for Heat Shocking
- Bivalve molluscs must come from approved growing areas and/or have undergone relaying in an approved relaying area or depuration in an approved depuration centre or tank.
- Each establishment that heat shucks bivalve molluscs should develop a heat shuck process schedule, acceptable to the official agency having jurisdiction.
- The heat shuck process schedule should address critical factors such as the species and size of bivalve molluscs, time of exposure to heat, internal bivalve molluscs temperature, type of heat process used, water/steam to bivalve molluscs ratios, nature of heat equipment, measurement devices, and their calibration, post-heating chilling operations, cleaning and sanitizing of heat process equipment.
- All bivalve molluscs should be washed with pressurized potable water or clean seawater and culled for damaged and dead bivalve molluscs prior to heat treatment.
- Before heat shocking, the bivalve molluscs should be inspected to determine that they are alive and not badly damaged.
- Heat-shocked bivalve molluscs should be cooled to 7 °C or below within two hours of being heat-treated (this time includes the shucking process).
- The heat-shocked bivalve molluscs should be packaged as soon as possible.
- Before packaging, the bivalve molluscs should be examined for objectionable matter such as shell pieces.
Transportation, Storage, and Distribution
- The transportation of live bivalve molluscs from a growing area to a distribution centre, depuration centre, relaying area, or establishment should be accompanied by documentation for the identification of batches of live bivalve molluscs.
- Storage and transportation temperatures should be indicated.
- Permanent, legible, and dated records of relaying and depuration should be kept concerning each lot.
- These records should be retained for a period of at least one year.
- Depuration centres or tanks and distribution centres and establishments should only accept lots of live bivalve molluscs with documentation issued by or accepted by the official agency having jurisdiction.
Documentation Requirements
- The documentation should contain the following information:
- The gatherer's identity and signature
- The date of harvesting
- Common and/or scientific name and quantity of bivalve molluscs
- The location of the growing area and the status of this area
- For distribution centres and establishments, if appropriate, the date and duration of depuration and the identity and signature of the person responsible
- For distribution centres and establishments, if appropriate, the date and duration of relaying, the location of the relaying area, and the identity and signature of the person responsible
- Complete records of harvest area and date of harvest and length of time of relaying or depuration of each lot should be maintained by the distribution centre or establishment for a period designated by the official agency having jurisdiction.
Product Tracing and Record-Keeping
- Each product should have an easily identifiable lot number.
- The lot number must include an identification code, the number of the establishment that distributes the product, the country of origin, and the day and month of packaging, in order to facilitate the traceability/product tracing of the product.
- A record-keeping system should be based on these lot numbers so that individual lots of bivalve molluscs can be traced from the growing area to the end user.
Ensuring the safety of bivalve molluscs involves identifying, classifying and monitoring areas, and controlling faecal contamination. Competent authorities, fishers, and producers collaborate to achieve this.
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