285
1992). The greater log reduction in population of V. vulnificus frozen by cryogenic
freezing compared to air blast freezing was determined by Espinoza Rodezno et al.
(2013). However, it was determined that both freezing methods is not effective on
reduction of V. parahaemolitycus population. This is thought to be since the fact that
V. parahaemolyticus tolerates low temperatures more than V. vulnificus because of
rapid and severe morphological changes during cold stress.
The application of pressure is reported to inactivate vibrios in shellfish. The
application of pressure is reported to inactivate vibrios in shellfish. Vibrios are more
sensitive to pressure than most other bacteria. Because they have a cell membrane
that can be inactivated at pressure levels ranging from 200 to 350 MPa (Espinoza
2013). It was reported that V. vulnificus, V. parahaemolyticus and V. cholerae are
sensitive to high hydrostatic pressure treatment at pressure levels between 200 and
300 MPa (Berlin et al. 1999). The initial V. parahaemolyticus population
(8.4 × 105–3.4 × 107 cfu/g) reduced to non-detectable levels in Pacific oysters
(Crassostrea gigas) after 345 MPa for 30 and 90 s (Calik et al. 2002). A reduction
of 5-log of V. parahaemolyticus and V. vulnificus, achieved with high pressure processing of 300 MPa for 180 s and 250 MPa for 120 s respectively has been reported
(Cook 2003).
5.2.1.2 Salmonella
Another bacterium related to human health is Salmonella. Salmonella spp. are
Gram-negative, rod-shaped enteric bacteria, human and animal wastes are sources
of Salmonella and are therefore ubiquitous in polluted water environments. Since
bacteria are resistant to physicochemical factors, they are present in surface and
groundwater (Soniat 2009). Microorganisms belonging to the genus Salmonella are
not natural inhabitants of the aquatic environment, but several Salmonella serovars
are widely distributed in the sea, river mouth and river waters, and in various seafood such as molluscs, shrimp, oysters, and various fish species. The presence of
these microorganisms in aquatic products and environments where they grow is
mainly due to hygiene errors during production (Li et al. 2009; Novoslavskij et al.
2016). Salmonella, introducing into the marine environment, can contaminate the
fauna, especially molluscan shellfish products. Although it has been reported to be
isolated from fish, shrimp, clams, mussels, oysters, crabs, lobsters, squid, cuttlefish,
and octopus (Kumar et al. 2009), there are few studies on Salmonella in various
shellfish there are few studies on Salmonella in various shellfish (Martinez-Urtaza
et al. 2004). It has been reported that salmonellosis is one of the most important
bacteria in food poisoning epidemics in the world, in most cases poisoning is associated with seafood, especially shellfish consumption, and the incidence of salmonellosis caused by the consumption of contaminated raw shellfish is the main
concern of the public health institutions and the seafood industry (Correa et al.
2006). Salmonella is among the most important causes of gastrointestinal disease
worldwide, and many countries that import seafood will restrict the import of raw
food products containing these pathogens. Salmonella occurs both in water and in
5.2 Microbial Risks
1992). The greater log reduction in population of V. vulnificus frozen by cryogenic
freezing compared to air blast freezing was determined by Espinoza Rodezno et al.
(2013). However, it was determined that both freezing methods is not effective on
reduction of V. parahaemolitycus population. This is thought to be since the fact that
V. parahaemolyticus tolerates low temperatures more than V. vulnificus because of
rapid and severe morphological changes during cold stress.
The application of pressure is reported to inactivate vibrios in shellfish. The
application of pressure is reported to inactivate vibrios in shellfish. Vibrios are more
sensitive to pressure than most other bacteria. Because they have a cell membrane
that can be inactivated at pressure levels ranging from 200 to 350 MPa (Espinoza
2013). It was reported that V. vulnificus, V. parahaemolyticus and V. cholerae are
sensitive to high hydrostatic pressure treatment at pressure levels between 200 and
300 MPa (Berlin et al. 1999). The initial V. parahaemolyticus population
(8.4 × 105–3.4 × 107 cfu/g) reduced to non-detectable levels in Pacific oysters
(Crassostrea gigas) after 345 MPa for 30 and 90 s (Calik et al. 2002). A reduction
of 5-log of V. parahaemolyticus and V. vulnificus, achieved with high pressure processing of 300 MPa for 180 s and 250 MPa for 120 s respectively has been reported
(Cook 2003).
5.2.1.2 Salmonella
Another bacterium related to human health is Salmonella. Salmonella spp. are
Gram-negative, rod-shaped enteric bacteria, human and animal wastes are sources
of Salmonella and are therefore ubiquitous in polluted water environments. Since
bacteria are resistant to physicochemical factors, they are present in surface and
groundwater (Soniat 2009). Microorganisms belonging to the genus Salmonella are
not natural inhabitants of the aquatic environment, but several Salmonella serovars
are widely distributed in the sea, river mouth and river waters, and in various seafood such as molluscs, shrimp, oysters, and various fish species. The presence of
these microorganisms in aquatic products and environments where they grow is
mainly due to hygiene errors during production (Li et al. 2009; Novoslavskij et al.
2016). Salmonella, introducing into the marine environment, can contaminate the
fauna, especially molluscan shellfish products. Although it has been reported to be
isolated from fish, shrimp, clams, mussels, oysters, crabs, lobsters, squid, cuttlefish,
and octopus (Kumar et al. 2009), there are few studies on Salmonella in various
shellfish there are few studies on Salmonella in various shellfish (Martinez-Urtaza
et al. 2004). It has been reported that salmonellosis is one of the most important
bacteria in food poisoning epidemics in the world, in most cases poisoning is associated with seafood, especially shellfish consumption, and the incidence of salmonellosis caused by the consumption of contaminated raw shellfish is the main
concern of the public health institutions and the seafood industry (Correa et al.
2006). Salmonella is among the most important causes of gastrointestinal disease
worldwide, and many countries that import seafood will restrict the import of raw
food products containing these pathogens. Salmonella occurs both in water and in
5.2 Microbial Risks