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chemical reactions that normally occur in unfrozen foods. A good freezing process
followed by cold storage ensures that shellfish are kept for months or even a year
or longer.
Freezing lobster is attractive for restaurant operators and supermarkets because
it makes it easier to buy and stock lobster. It is better to freeze them because it is
difficult to keep the lobsters alive until they are consumed. Freezing also makes it
easier to ship lobsters to more places: sellers do not have to worry about lobsters
dying if the temperature changes or a truck or plane is delayed. Because processors
can stockpile frozen lobster more readily, the price also tends to be more stable
(Porter 2019).
An important problem in the freezing of live lobsters is the adhesion of meat to
the shell and the difficulty in removing the shell by consumers. Therefore, it is recommended to heat the lobsters before freezing. Thus, the destruction of the tissues
that connect the flesh to the shell occurs (Work et al. 1997). In order to activate the
protection of the freezing process, suitable pre-treatments must be carried out
according to the type of crustacean. The pre-treatment for lobsters is usually cooked
in brine solution. The lobsters are cooked in 3% saline for 10–20 min. In some lobster species, the tail is separated from the body to remove the intestines. Frozen
lobsters are reported to have a shelf life of 3 months at a temperature of −23 °C or
less (Noomhorm and Vongsawasdi 2004).
The effects of freezing methods on the quality of lobster are important. Rapid
freezing has been recommended to prevent the formation of large ice crystals. The
large crystals can damage cells and allow the loss of moisture during the frozen storage and upon thawing. Slow freezing result in an inferior quality product due mainly
to protein denaturation. The design of the freezer depends largely on the type of
product to be frozen, the duration of freezing and the amount of raw material.
Various freezing methods are currently available. These are sharp freezing, plate
freezing, blast freezing, cryogenic freezing, liquid nitrogen freezing, carbon dioxide
freezing, spray or dipping freezing and pressure shift freezing. These methods have
advantages and disadvantages and therefore the appropriate method for the product
should be determined (Noomhorm and Vongsawasdi 2004). It has been reported that
cooked crayfish (Procambarus clarkii) can be stored at −20 °C for 6 months after
freezing at different freezing rates (Zhao et al. 2014).
In a study (Work et al. 1997), soft- and hard-shell lobsters (whole, claw and tail)
were cryogenically frozen as using liquid CO 2 and compared their quality during
frozen storage for 9 months. In hard shell claw meat, higher lobster flavour was
determined with soft shell claw. The soft-shell claws contained more moisture.
During storage, soft- and hard-shell tail meats had a good lobster flavour. Higher
tenderness scores were obtained for soft shell tails.
In the other study, a part of the lobster krill (Munida spp.) was packaged in polyethylene bags and immediately frozen at −30 °C. Other part was divided into two
groups. The first group was immersed into water and the second group was immersed
into sodium metabisulphite solution. All samples were packaged in polyethylene
bags and stored at −30 °C. After 2 days, at all bags were placed at −18 °C. According
to the results of the study, it was determined that pre-immersion in SMB on one
2.3 Lobsters
chemical reactions that normally occur in unfrozen foods. A good freezing process
followed by cold storage ensures that shellfish are kept for months or even a year
or longer.
Freezing lobster is attractive for restaurant operators and supermarkets because
it makes it easier to buy and stock lobster. It is better to freeze them because it is
difficult to keep the lobsters alive until they are consumed. Freezing also makes it
easier to ship lobsters to more places: sellers do not have to worry about lobsters
dying if the temperature changes or a truck or plane is delayed. Because processors
can stockpile frozen lobster more readily, the price also tends to be more stable
(Porter 2019).
An important problem in the freezing of live lobsters is the adhesion of meat to
the shell and the difficulty in removing the shell by consumers. Therefore, it is recommended to heat the lobsters before freezing. Thus, the destruction of the tissues
that connect the flesh to the shell occurs (Work et al. 1997). In order to activate the
protection of the freezing process, suitable pre-treatments must be carried out
according to the type of crustacean. The pre-treatment for lobsters is usually cooked
in brine solution. The lobsters are cooked in 3% saline for 10–20 min. In some lobster species, the tail is separated from the body to remove the intestines. Frozen
lobsters are reported to have a shelf life of 3 months at a temperature of −23 °C or
less (Noomhorm and Vongsawasdi 2004).
The effects of freezing methods on the quality of lobster are important. Rapid
freezing has been recommended to prevent the formation of large ice crystals. The
large crystals can damage cells and allow the loss of moisture during the frozen storage and upon thawing. Slow freezing result in an inferior quality product due mainly
to protein denaturation. The design of the freezer depends largely on the type of
product to be frozen, the duration of freezing and the amount of raw material.
Various freezing methods are currently available. These are sharp freezing, plate
freezing, blast freezing, cryogenic freezing, liquid nitrogen freezing, carbon dioxide
freezing, spray or dipping freezing and pressure shift freezing. These methods have
advantages and disadvantages and therefore the appropriate method for the product
should be determined (Noomhorm and Vongsawasdi 2004). It has been reported that
cooked crayfish (Procambarus clarkii) can be stored at −20 °C for 6 months after
freezing at different freezing rates (Zhao et al. 2014).
In a study (Work et al. 1997), soft- and hard-shell lobsters (whole, claw and tail)
were cryogenically frozen as using liquid CO 2 and compared their quality during
frozen storage for 9 months. In hard shell claw meat, higher lobster flavour was
determined with soft shell claw. The soft-shell claws contained more moisture.
During storage, soft- and hard-shell tail meats had a good lobster flavour. Higher
tenderness scores were obtained for soft shell tails.
In the other study, a part of the lobster krill (Munida spp.) was packaged in polyethylene bags and immediately frozen at −30 °C. Other part was divided into two
groups. The first group was immersed into water and the second group was immersed
into sodium metabisulphite solution. All samples were packaged in polyethylene
bags and stored at −30 °C. After 2 days, at all bags were placed at −18 °C. According
to the results of the study, it was determined that pre-immersion in SMB on one
2.3 Lobsters