96
Drowning
Lobsters can be killed by changing salinity. When they are immersed in fresh water,
they slowly die as salt may be lost from their blood. Hyposaline conditions prevent
loss of extremity in lobsters.
In a study, crayfish Astacus (Astacus astacus, and Astacus leptodactilus) and
American lobster (Homarus americanus) were anesthetized using four different
methods (addition of MgCl 2 to the holding water, cooling, bubbling holding water
with CO 2 and electric stunning). Neuronal responses of the animals were measured
via implanting electrodes in central nervous system (CNS) According to the results
of the study, it was determined that cooling with MgCl 2 (10%) did not anaesthetized
lobster and crayfish, and CO 2 was partially effective due to low pH in water. On the
other hand, cooling did not show any anaesthetic effect. Anaesthetic effect of electric stunning was determined (Fregin and Bickmeyer 2016).
2.3.3 Quality Changes in Lobsters
Shellfish have a short shelf life due to their small size, lack of intestine removal,
high levels of non-protein nitrogen compounds, polyunsaturated fatty acids and
melanin pigments. Thus, post‐mortem autolytic changes, microbial spoilage, melanosis development and lipid oxidation are affected quality of crustaceans and limited their shelf life (Rosa and Nunes 2004; Ashie et al. 1996b).
Lobsters are marketed as whole or as tails. Lobster tails are sometimes removed
after catch and the heads discarded. It is thought that tailing process can affect the
quality and the shelf-life of the product. It is reported that if the lobsters are damaged during catching in Icelandic fishery, muscle disruption called “skyrhumar” can
be seen in Norway lobsters. This has been reported to be caused by the release of
proteases from the hepatopancreas of the nephrops into the abdominal muscles (tail
flesh). It is stated that this process is related to the crushing of animals that may
cause crushing of cephalothorax during trawling and releasing hepatopancreas
enzymes to abdominal muscle (Neil 2012). Accordingly, removal of the head (containing the hepatopancreas) from the tail should reduce the onset of “skyrhumar”.
Especially after catching, tailing is very important in terms of onset of “skyrhumar”
at sea. In one study, lobster tails which were tailed immediately after being caught
were first cooled at 0 °C and then frozen at −24 °C. For comparison purposes, the
lobsters were taken from the same catch and tailed in a processing plant on land and
frozen. As a result of the research, the “skyrhumar” index of the lobsters whose was
tailed immediately after catching was found to be very low (Gunnarsson 2010).
Removal of the internal organs is effective in reducing the bacterial load of some
seafood. Tailing can also be thought to be effective in reducing the internal bacteria
in the stomach of lobster. In this study, it was determined that tailing had no effect
on the total plate count of Norwegian lobster. Although the stomach was removed
by tailing, it was stated that the intestinal tract was not removed, and the tailing was
not effective in reducing bacteria in lobster (Bekaert et al. 2015).
2 Crustacean Shellfish
Drowning
Lobsters can be killed by changing salinity. When they are immersed in fresh water,
they slowly die as salt may be lost from their blood. Hyposaline conditions prevent
loss of extremity in lobsters.
In a study, crayfish Astacus (Astacus astacus, and Astacus leptodactilus) and
American lobster (Homarus americanus) were anesthetized using four different
methods (addition of MgCl 2 to the holding water, cooling, bubbling holding water
with CO 2 and electric stunning). Neuronal responses of the animals were measured
via implanting electrodes in central nervous system (CNS) According to the results
of the study, it was determined that cooling with MgCl 2 (10%) did not anaesthetized
lobster and crayfish, and CO 2 was partially effective due to low pH in water. On the
other hand, cooling did not show any anaesthetic effect. Anaesthetic effect of electric stunning was determined (Fregin and Bickmeyer 2016).
2.3.3 Quality Changes in Lobsters
Shellfish have a short shelf life due to their small size, lack of intestine removal,
high levels of non-protein nitrogen compounds, polyunsaturated fatty acids and
melanin pigments. Thus, post‐mortem autolytic changes, microbial spoilage, melanosis development and lipid oxidation are affected quality of crustaceans and limited their shelf life (Rosa and Nunes 2004; Ashie et al. 1996b).
Lobsters are marketed as whole or as tails. Lobster tails are sometimes removed
after catch and the heads discarded. It is thought that tailing process can affect the
quality and the shelf-life of the product. It is reported that if the lobsters are damaged during catching in Icelandic fishery, muscle disruption called “skyrhumar” can
be seen in Norway lobsters. This has been reported to be caused by the release of
proteases from the hepatopancreas of the nephrops into the abdominal muscles (tail
flesh). It is stated that this process is related to the crushing of animals that may
cause crushing of cephalothorax during trawling and releasing hepatopancreas
enzymes to abdominal muscle (Neil 2012). Accordingly, removal of the head (containing the hepatopancreas) from the tail should reduce the onset of “skyrhumar”.
Especially after catching, tailing is very important in terms of onset of “skyrhumar”
at sea. In one study, lobster tails which were tailed immediately after being caught
were first cooled at 0 °C and then frozen at −24 °C. For comparison purposes, the
lobsters were taken from the same catch and tailed in a processing plant on land and
frozen. As a result of the research, the “skyrhumar” index of the lobsters whose was
tailed immediately after catching was found to be very low (Gunnarsson 2010).
Removal of the internal organs is effective in reducing the bacterial load of some
seafood. Tailing can also be thought to be effective in reducing the internal bacteria
in the stomach of lobster. In this study, it was determined that tailing had no effect
on the total plate count of Norwegian lobster. Although the stomach was removed
by tailing, it was stated that the intestinal tract was not removed, and the tailing was
not effective in reducing bacteria in lobster (Bekaert et al. 2015).
2 Crustacean Shellfish