177
intensive and as labour costs increase and qualified shuckers become harder to find,
profit margins may be reduced (Martin and Hall 2006). During shucking by hand, a
sharp knife is inserted between the shells, cutting the adductor muscle, and opening
the oyster. This requires a skilled workforce, as not only is the process hazardous
but inexpert handling can damage the oyster meat, reducing the quality and appearance of the finished product (Cruz-Romero et al. 2007).
Because of the difficulties of manual shucking, other techniques have been
developed for shucking the oysters. Some devices and machines shucking the oysters mechanically have been developed.
Because of being a filter feeder and accumulating bacteria and viruses from the
water it inhabits, it is one of the dominant bivalves in seafood-borne diseases. They
are generally consumed whole and raw. Therefore, they create risks for consumers.
In recent years, a process has been developed a method eliminating pathogenic bacteria. It has been reported that HP treatment provides a significant advantage in
detaching the oyster adductor muscle from the shell. HP treatment at 241 MPa for
2 min caused detachment of adductor muscle in 88% of oysters (Crassostrea gigas),
while treatment at 310 MPa, with immediate pressure release, resulted in 100%
efficiency of shucking (He et al. 2002). In a study comparing the effects of high
pressure (260 Mpa for 3 min) and heat treatment (50 °C for 10 min and 75 °C for
8 min) applied to the oysters, it was determined that the yield was higher with
HP. Because, adductor muscle of oyster was not cut, so that the oyster retained all
its moisture (Cruz-Romero et al. 2007). Moreover, recovered oyster meat has been
reported to have a good shape and appearance (Lopez-Caballero et al. 2000). HP
processed oysters can be shucked with minimal effort and skill, as the consumer
only needs to remove the surrounding band to open the processed oyster. In addition
to reduced labour cost and risks, and the safety of the product is improved (CruzRomero et al. 2007). The process calls for 100–800 MPa of hydrostatic pressure to
destroy pathogenic organisms and separate the adductor muscle from the shell. HP
treatment makes the seafood safe for eating in raw condition due to the inactivation
of microorganisms. Vibrio species have been reported to be susceptible at pressures
of 200–300 MPa (Berlin et al. 1999). HP treatment of 345 MPa for 90 s reduced
Vibrio parahaemolyticus in Pacific oysters (Crassostrea gigas) (Calik et al. 2002).
Moreover, Hydrostatic pressure has been reported to have no significant effect on
the sensory and nutritional properties of oysters. The biggest drawback of this
method is that it is expensive and requires high investment expenses. HP application
to Pacific oysters (Crassostrea gigas) with pressure between 207 and 310 MPa at 0,
1, and 2 min reduced initial microbial load by 2–3 logs and counts remained at a
reduced level through the storage study (He et al. 2002).
Fitting of oysters with heat-shrinkable plastic bands before treatment holds the
shells together and reduces the loss of interval fluid. Oysters treated in this way do
not gape but can be shucked with minimal effort and skill (Murchie et al. 2005).
3.1 Bivalves
intensive and as labour costs increase and qualified shuckers become harder to find,
profit margins may be reduced (Martin and Hall 2006). During shucking by hand, a
sharp knife is inserted between the shells, cutting the adductor muscle, and opening
the oyster. This requires a skilled workforce, as not only is the process hazardous
but inexpert handling can damage the oyster meat, reducing the quality and appearance of the finished product (Cruz-Romero et al. 2007).
Because of the difficulties of manual shucking, other techniques have been
developed for shucking the oysters. Some devices and machines shucking the oysters mechanically have been developed.
Because of being a filter feeder and accumulating bacteria and viruses from the
water it inhabits, it is one of the dominant bivalves in seafood-borne diseases. They
are generally consumed whole and raw. Therefore, they create risks for consumers.
In recent years, a process has been developed a method eliminating pathogenic bacteria. It has been reported that HP treatment provides a significant advantage in
detaching the oyster adductor muscle from the shell. HP treatment at 241 MPa for
2 min caused detachment of adductor muscle in 88% of oysters (Crassostrea gigas),
while treatment at 310 MPa, with immediate pressure release, resulted in 100%
efficiency of shucking (He et al. 2002). In a study comparing the effects of high
pressure (260 Mpa for 3 min) and heat treatment (50 °C for 10 min and 75 °C for
8 min) applied to the oysters, it was determined that the yield was higher with
HP. Because, adductor muscle of oyster was not cut, so that the oyster retained all
its moisture (Cruz-Romero et al. 2007). Moreover, recovered oyster meat has been
reported to have a good shape and appearance (Lopez-Caballero et al. 2000). HP
processed oysters can be shucked with minimal effort and skill, as the consumer
only needs to remove the surrounding band to open the processed oyster. In addition
to reduced labour cost and risks, and the safety of the product is improved (CruzRomero et al. 2007). The process calls for 100–800 MPa of hydrostatic pressure to
destroy pathogenic organisms and separate the adductor muscle from the shell. HP
treatment makes the seafood safe for eating in raw condition due to the inactivation
of microorganisms. Vibrio species have been reported to be susceptible at pressures
of 200–300 MPa (Berlin et al. 1999). HP treatment of 345 MPa for 90 s reduced
Vibrio parahaemolyticus in Pacific oysters (Crassostrea gigas) (Calik et al. 2002).
Moreover, Hydrostatic pressure has been reported to have no significant effect on
the sensory and nutritional properties of oysters. The biggest drawback of this
method is that it is expensive and requires high investment expenses. HP application
to Pacific oysters (Crassostrea gigas) with pressure between 207 and 310 MPa at 0,
1, and 2 min reduced initial microbial load by 2–3 logs and counts remained at a
reduced level through the storage study (He et al. 2002).
Fitting of oysters with heat-shrinkable plastic bands before treatment holds the
shells together and reduces the loss of interval fluid. Oysters treated in this way do
not gape but can be shucked with minimal effort and skill (Murchie et al. 2005).
3.1 Bivalves