191
Commercial manual shucking is done by highly skilled people and requires considerable strength, persistence, ability, experience, willingness. However, manual
shucking, even by skilled people, may result in damage to the edible parts with yield
loss and quality reduction. Also, the efficiency of manual shucking is low (Yi et al.
2013). The recovery of meat in shucking of scallops is very important. Incomplete
recovery causes economic losses. The on-board shucking of the scallops is fast, and
losses are also observed during commercial rapid shucking. In scallops (Chlamys
islandica and Placopecten magellanicus) shucked at sea by an experienced fisherman scallop, losses were seen depending the size. The average loss for commercial
size scallop was found to be 11%. It is recommended that the process be performed
more slowly as commercial fast shucking causes the losses in meat yield, but it has
been reported that it should be investigated whether it will cause additional labour
costs (Naidu 1987).
Because of these difficulties in manual shucking, many shucking methods have
been developed, especially for oysters (Yi et al. 2013). It was reported that the
invention of a machine that automatically notches and separates shells, cuts flesh
and separates shells from meat for the first time in 1907 was patented (Martin and
Hall 2006). Subsequently, patents have been reported in which invented devices and
apparatus that mechanically shocking of scallops (Doiron 1949; Brown 1967;
Wenstrom and Gorton 1985).
Bay and calico scallops usually are shucked on land. Their small size makes then
uneconomical to shuck by hand on-board ship. Calico scallops are shucked mechanically. Machines that employ a shock-heat-shock method have been used. In this
process, the scallops are passed through a sorter to remove trash and then are fed
into a tank of water heated to 80–100 °C or through a steam tunnel. Rollers that
revolve in opposite directions grip the shells and sling them with considerable force
against a steel baffle slanted at a 45″ angle. They are removed by conveyor and
undergo a second shock-heat-shock treatment. They are then dropped onto a vibrating screen that separates the meat and viscera from the shells. The meat then goes
to an eviscerator, basically several paired rollers that grips and pulls the viscera
from the meat. The meat is then washed, or it may be placed in a brine tank to
remove shell fragments (Hackney and Rippen 2000).
In addition, thermal methods and freezing process are also used for shucking
bivalves. However, since these products are generally consumed raw, the thermal
method is not preferred in these cases. Although the process of freezing breaks the
bond between the muscle and the shell, this may not always be complete.
High hydrostatic pressure (HHP) is an alternative for shucking of bivalve. HHP
systems can ensure that shellfish are kept raw and that the connection between the
adductor muscle and shell is completely and reliably released in high efficiency
(Murchie et al. 2005). In a study conducted by Yi et al. (2013), Bay scallops
(Argopecten irradians) were shucked with HHP in different pressures and times and
compared with scallops shucked by hand using knife. It has been concluded that
100% detachment of the adductor muscle was observed when treated at
200 MPa/3 min and 350 MPa/0 min and higher yields were obtained HHP-shucked
than those manual shucked samples.
3.1 Bivalves
Commercial manual shucking is done by highly skilled people and requires considerable strength, persistence, ability, experience, willingness. However, manual
shucking, even by skilled people, may result in damage to the edible parts with yield
loss and quality reduction. Also, the efficiency of manual shucking is low (Yi et al.
2013). The recovery of meat in shucking of scallops is very important. Incomplete
recovery causes economic losses. The on-board shucking of the scallops is fast, and
losses are also observed during commercial rapid shucking. In scallops (Chlamys
islandica and Placopecten magellanicus) shucked at sea by an experienced fisherman scallop, losses were seen depending the size. The average loss for commercial
size scallop was found to be 11%. It is recommended that the process be performed
more slowly as commercial fast shucking causes the losses in meat yield, but it has
been reported that it should be investigated whether it will cause additional labour
costs (Naidu 1987).
Because of these difficulties in manual shucking, many shucking methods have
been developed, especially for oysters (Yi et al. 2013). It was reported that the
invention of a machine that automatically notches and separates shells, cuts flesh
and separates shells from meat for the first time in 1907 was patented (Martin and
Hall 2006). Subsequently, patents have been reported in which invented devices and
apparatus that mechanically shocking of scallops (Doiron 1949; Brown 1967;
Wenstrom and Gorton 1985).
Bay and calico scallops usually are shucked on land. Their small size makes then
uneconomical to shuck by hand on-board ship. Calico scallops are shucked mechanically. Machines that employ a shock-heat-shock method have been used. In this
process, the scallops are passed through a sorter to remove trash and then are fed
into a tank of water heated to 80–100 °C or through a steam tunnel. Rollers that
revolve in opposite directions grip the shells and sling them with considerable force
against a steel baffle slanted at a 45″ angle. They are removed by conveyor and
undergo a second shock-heat-shock treatment. They are then dropped onto a vibrating screen that separates the meat and viscera from the shells. The meat then goes
to an eviscerator, basically several paired rollers that grips and pulls the viscera
from the meat. The meat is then washed, or it may be placed in a brine tank to
remove shell fragments (Hackney and Rippen 2000).
In addition, thermal methods and freezing process are also used for shucking
bivalves. However, since these products are generally consumed raw, the thermal
method is not preferred in these cases. Although the process of freezing breaks the
bond between the muscle and the shell, this may not always be complete.
High hydrostatic pressure (HHP) is an alternative for shucking of bivalve. HHP
systems can ensure that shellfish are kept raw and that the connection between the
adductor muscle and shell is completely and reliably released in high efficiency
(Murchie et al. 2005). In a study conducted by Yi et al. (2013), Bay scallops
(Argopecten irradians) were shucked with HHP in different pressures and times and
compared with scallops shucked by hand using knife. It has been concluded that
100% detachment of the adductor muscle was observed when treated at
200 MPa/3 min and 350 MPa/0 min and higher yields were obtained HHP-shucked
than those manual shucked samples.
3.1 Bivalves