147
Freezing of Mussels
Shellfish keep their shells tightly closed. If the shell is open, should be tapped it
lightly. The shellfish should respond by snapping the shell closed. If it does not
respond, it is dead. The dead ones should be discarded immediately. They should be
kept solidly frozen. Should not be thawed and re-frozen them. Repeated freezing
and thawing reduce the quality of the shellfish and allows spoiling. They should be
thawed only enough for the number of servings needed and thawed in the refrigerator on the day to be used.
The mussel-freezing process starts with cooked and shucked meat. It is frozen as
blocks which are laid out on trays. Mussel meats are proper to either the plate freezing or the air blast freezing process, since the meats are small and provide good
surface contact with the cooling medium (Waterman 1963). The freezing process is
usually carried out in blast freezers at −40 °C for a long enough time to obtain a
temperature of −20 °C in the geometrical centre of the mussel meat block. The
process normally takes approximately 50 min. The meats may be packed in a variety of containers before freezing, for example waxed cartons or polythene bags, or
may be frozen unwrapped and packed or glazed afterwards. The unwrapped meat is
glazed to mitigate the water loss by evaporation. Finally, glazed and not necessarily
packed meats are stored in a cold room at a temperature of −20 °C. Their shelf-life
under these conditions should be 8–9 months. Thawed meats after 8–9 months storage will then be in excellent condition with flavour and texture equal to fresh
(Waterman 1963; Almonacid et al. 2015).
Thawing of the meats in 10° salt solution, or soaking the thawed meats in a similar solution, may enhance the flavour, the salt acting as a condiment; the use of salt
during cooking or subsequent rinsing of the meats before freezing may however
accelerate the development of off flavours in the frozen meats during cold storage
(Waterman 1963).
Mussels should be pre-cooled for effective and rapid freezing. This will also
affect product quality. In a study examining the effect of pre-cooling with ice on the
quality and shelf life of frozen mussels (M. edulis), freshly frozen mussels remained
acceptable for 40 weeks, while the mussels frozen after ice storage of 8 days were
kept acceptable for only15 weeks (Chinnamma 1973).
The quality and shelf life of frozen seafood varies depending on the biological
differences and pre-freezing processes. If the product is initially of poor quality, its
shelf life is also significantly reduced. In addition, storage conditions and storage
time greatly affect the quality of the final product (Gokoglu 2002). In various studies, different shelf life periods were determined for mussels frozen under different
freezing and storage conditions. Gokoglu et al. (2000) have determined a shelf life
of 4 months for mussels (M. galloprovincialis) frozen and stored at −20 °C. During
the storage, trimethylamine (TMA-N) total volatile bases (TVB-N) and pH values
increased, and sensory acceptability decreased.
Some researchers have used some preservatives to maintain the quality and
improve storage stability of frozen mussels. Kaba and Erkoyuncu (2005) have
treated mussels with sodium tripolyphosphate before freezing and determined that
3.1 Bivalves
Freezing of Mussels
Shellfish keep their shells tightly closed. If the shell is open, should be tapped it
lightly. The shellfish should respond by snapping the shell closed. If it does not
respond, it is dead. The dead ones should be discarded immediately. They should be
kept solidly frozen. Should not be thawed and re-frozen them. Repeated freezing
and thawing reduce the quality of the shellfish and allows spoiling. They should be
thawed only enough for the number of servings needed and thawed in the refrigerator on the day to be used.
The mussel-freezing process starts with cooked and shucked meat. It is frozen as
blocks which are laid out on trays. Mussel meats are proper to either the plate freezing or the air blast freezing process, since the meats are small and provide good
surface contact with the cooling medium (Waterman 1963). The freezing process is
usually carried out in blast freezers at −40 °C for a long enough time to obtain a
temperature of −20 °C in the geometrical centre of the mussel meat block. The
process normally takes approximately 50 min. The meats may be packed in a variety of containers before freezing, for example waxed cartons or polythene bags, or
may be frozen unwrapped and packed or glazed afterwards. The unwrapped meat is
glazed to mitigate the water loss by evaporation. Finally, glazed and not necessarily
packed meats are stored in a cold room at a temperature of −20 °C. Their shelf-life
under these conditions should be 8–9 months. Thawed meats after 8–9 months storage will then be in excellent condition with flavour and texture equal to fresh
(Waterman 1963; Almonacid et al. 2015).
Thawing of the meats in 10° salt solution, or soaking the thawed meats in a similar solution, may enhance the flavour, the salt acting as a condiment; the use of salt
during cooking or subsequent rinsing of the meats before freezing may however
accelerate the development of off flavours in the frozen meats during cold storage
(Waterman 1963).
Mussels should be pre-cooled for effective and rapid freezing. This will also
affect product quality. In a study examining the effect of pre-cooling with ice on the
quality and shelf life of frozen mussels (M. edulis), freshly frozen mussels remained
acceptable for 40 weeks, while the mussels frozen after ice storage of 8 days were
kept acceptable for only15 weeks (Chinnamma 1973).
The quality and shelf life of frozen seafood varies depending on the biological
differences and pre-freezing processes. If the product is initially of poor quality, its
shelf life is also significantly reduced. In addition, storage conditions and storage
time greatly affect the quality of the final product (Gokoglu 2002). In various studies, different shelf life periods were determined for mussels frozen under different
freezing and storage conditions. Gokoglu et al. (2000) have determined a shelf life
of 4 months for mussels (M. galloprovincialis) frozen and stored at −20 °C. During
the storage, trimethylamine (TMA-N) total volatile bases (TVB-N) and pH values
increased, and sensory acceptability decreased.
Some researchers have used some preservatives to maintain the quality and
improve storage stability of frozen mussels. Kaba and Erkoyuncu (2005) have
treated mussels with sodium tripolyphosphate before freezing and determined that
3.1 Bivalves