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Depuration of Mussel
Mussels, oysters, and clams are filter feeders and accumulate pathogenic bacteria.
Depuration is defined as a process utilizing the natural water-filtering mechanism of
shellfish to release contaminants from the digestive tract into clean and unpolluted
water. Depuration is intended to reduce the number of pathogenic organisms that
may be present in shellfish harvested from moderately polluted (restricted) waters
to such levels that the shellfish will be acceptable for human consumption without
further processing. The process is not intended for shellfish from heavily polluted
(prohibited) waters nor to reduce the levels of poisonous or deleterious substances
that the shellfish may have accumulated from their environment (NSSP 2017). This
treatment can also remove most of the sand in the stomach. Depuration of mussels
is necessity before marketing due to increasing of pollution of seawater. Those most
widely subjected to the process include oysters, mussels, and clams. It is essential
to employ depuration in order to remove or reduce the bacteria load causing typhoid
and viruses causing gastroenteritis (non-typhi Salmonellae and Campylobacter) and
infectious hepatitis accumulated in bivalves from the marine environment before
human consumption (Singh and Nagalakshimi 2013). Some species such as cockles, scallops and razor clams pose specific challenges to depuration, for example the
mobility of scallops makes them difficult to contain in baskets and to prevent them
stirring up settled detritus. While depuration may be the only mitigation strategy for
those species eaten raw, such as oysters, many other species of bivalves are lightly
cooked before eating and depuration will provide an additional safeguard (FAO
2008). In the process of filter-feeding bivalve molluscs may also concentrate and
retain human pathogens derived from sewage contamination of growing waters. The
hazards posed by bioaccumulation are compounded by the traditional consumption
of molluscan shellfish raw or after minimal heat treatment and by consumption of
the entire animal, including the viscera. Depuration processes are applied to shellfish such as oysters, mussels, scallops, and clams that are sold alive. Shellfish, which
are commercially marketed and consumed as food in many parts of the world, are
supplied to the market by reaching the hygienic conditions determined by the depuration process.
Purification, also known as depuration, involves the transfer of the molluscs from
the harvesting area to enclosed systems with flowing clean water with the appropriate salinity and temperature. Here, the molluscs continue filtration and normal
digestive activity and over a period of about 48 h, they purge themselves of most
bacterial contamination present, although under certain conditions, longer depuration periods may be required for adequate purification (Martinez et al. 2009).
Depuration starts by placing shellfish into tanks containing clean sea water.
Thus, the animals continue their normal feeding activity (filtration) and, after a
period, remove microorganisms that cause diseases through the gills and the intestine. By removing the wastes accumulated at the bottom of the tanks in certain
periods, it is ensured that microbial hazards removed from the animal body do not
re-enter the organism. After depuration process, the bivalve products should remain
alive while packaging and the quality of the product must be maintained. Resumption
3 Molluscan Shellfish
Depuration of Mussel
Mussels, oysters, and clams are filter feeders and accumulate pathogenic bacteria.
Depuration is defined as a process utilizing the natural water-filtering mechanism of
shellfish to release contaminants from the digestive tract into clean and unpolluted
water. Depuration is intended to reduce the number of pathogenic organisms that
may be present in shellfish harvested from moderately polluted (restricted) waters
to such levels that the shellfish will be acceptable for human consumption without
further processing. The process is not intended for shellfish from heavily polluted
(prohibited) waters nor to reduce the levels of poisonous or deleterious substances
that the shellfish may have accumulated from their environment (NSSP 2017). This
treatment can also remove most of the sand in the stomach. Depuration of mussels
is necessity before marketing due to increasing of pollution of seawater. Those most
widely subjected to the process include oysters, mussels, and clams. It is essential
to employ depuration in order to remove or reduce the bacteria load causing typhoid
and viruses causing gastroenteritis (non-typhi Salmonellae and Campylobacter) and
infectious hepatitis accumulated in bivalves from the marine environment before
human consumption (Singh and Nagalakshimi 2013). Some species such as cockles, scallops and razor clams pose specific challenges to depuration, for example the
mobility of scallops makes them difficult to contain in baskets and to prevent them
stirring up settled detritus. While depuration may be the only mitigation strategy for
those species eaten raw, such as oysters, many other species of bivalves are lightly
cooked before eating and depuration will provide an additional safeguard (FAO
2008). In the process of filter-feeding bivalve molluscs may also concentrate and
retain human pathogens derived from sewage contamination of growing waters. The
hazards posed by bioaccumulation are compounded by the traditional consumption
of molluscan shellfish raw or after minimal heat treatment and by consumption of
the entire animal, including the viscera. Depuration processes are applied to shellfish such as oysters, mussels, scallops, and clams that are sold alive. Shellfish, which
are commercially marketed and consumed as food in many parts of the world, are
supplied to the market by reaching the hygienic conditions determined by the depuration process.
Purification, also known as depuration, involves the transfer of the molluscs from
the harvesting area to enclosed systems with flowing clean water with the appropriate salinity and temperature. Here, the molluscs continue filtration and normal
digestive activity and over a period of about 48 h, they purge themselves of most
bacterial contamination present, although under certain conditions, longer depuration periods may be required for adequate purification (Martinez et al. 2009).
Depuration starts by placing shellfish into tanks containing clean sea water.
Thus, the animals continue their normal feeding activity (filtration) and, after a
period, remove microorganisms that cause diseases through the gills and the intestine. By removing the wastes accumulated at the bottom of the tanks in certain
periods, it is ensured that microbial hazards removed from the animal body do not
re-enter the organism. After depuration process, the bivalve products should remain
alive while packaging and the quality of the product must be maintained. Resumption
3 Molluscan Shellfish