219
It was also tried to use of protective additives for octopus (Cistopus indicus) in
chilled storage. Two commercial additives which one of them consisted of a mixture
of sodium citrate and hydrogen peroxide, and other one is a mixture of sodium
citrate and sodium bicarbonate, were applied to octopus and stored with flake ice at
5 °C. However, it has been determined that these protective additives do affect neither the shelf life nor the sensory quality of the octopus (Manimaran et al. 2016b).
Freezing of Cephalopods
Since squid catches have increased substantially worldwide, it is an important
export product. Freezing is the most important and large scale preservation method
that facilitates exports for squid (Sukumar et al. 2014). As squid is a soft-bodied
species, it requires special handling during harvesting, processing and preservation
to maintain its quality as it can suffer physical and mechanical damage such as
breakage and tearing. Otherwise, market value and quality decrease. Squid also
contain multi-coloured chromatophores on the skin surface. These alter the colour
of the squid to match the ambient colour when swimming in the ocean. However,
after death, these chromatophores can expand or contract depending upon processing and storage temperatures (Learson 2000). In long-term storage, pink discoloration is seen on the skin. This is the breakdown of the chromophores in the skin. It
is generally reported that large squid are more sensitive to pink coloration than
small ones (Sungsri-in 2010). As the squid grading is mostly based on colour in the
market, its transport and storage techniques should be designed to preserve the surface colour and texture. Especially the colour of the surface is important for the
squid to be marketed as a whole, and less important for the squid which to be
skinned or subjected to further processing. Freezing at sea is the recommended
processing method for the whole, frozen squid market. Immediately after capture
the squid should be placed in refrigerated seawater (RSW) at 0°C to 4 °C. The cold
seawater prevents the squid from drying out and eliminates discoloration of the skin
surface. The squid should then be quickly sorted and packed, and either blast- or
plate-frozen at −30°C to −40 °C. Rapid freezing and constant storage at low temperatures are essential to avoid changes in colour and adverse textural changes.
Fluctuating storage temperatures can also result in reddening of the product surface
which reduces market value (Learson 2000).
The quality of cephalopods changes during frozen storage. Besides protein denaturation, oil oxidation and desiccation, odour and discoloration can be seen in frozen storage. Changes in squid during frozen storage have been studied by several
researchers. It has been reported that changes in seafood meat during freezing and
frozen storage are mainly related to the modification of myofibrilar proteins and the
potential impact of lipids on protein denaturation in relation to free fatty acids
(Sikorski et al. 1976). In frozen stored squid (Illex argentinus), a significant decrease
in protein solubility was detected in 5-month storage, and then remained unchanged
during storage (Paredi et al. 2006). Similar decreases have been reported for squid
(Loligo vulgaris), octopus (Octopus vulgaris) and cuttlefish (Sepia officinalis)
3.2 Cephalopods
It was also tried to use of protective additives for octopus (Cistopus indicus) in
chilled storage. Two commercial additives which one of them consisted of a mixture
of sodium citrate and hydrogen peroxide, and other one is a mixture of sodium
citrate and sodium bicarbonate, were applied to octopus and stored with flake ice at
5 °C. However, it has been determined that these protective additives do affect neither the shelf life nor the sensory quality of the octopus (Manimaran et al. 2016b).
Freezing of Cephalopods
Since squid catches have increased substantially worldwide, it is an important
export product. Freezing is the most important and large scale preservation method
that facilitates exports for squid (Sukumar et al. 2014). As squid is a soft-bodied
species, it requires special handling during harvesting, processing and preservation
to maintain its quality as it can suffer physical and mechanical damage such as
breakage and tearing. Otherwise, market value and quality decrease. Squid also
contain multi-coloured chromatophores on the skin surface. These alter the colour
of the squid to match the ambient colour when swimming in the ocean. However,
after death, these chromatophores can expand or contract depending upon processing and storage temperatures (Learson 2000). In long-term storage, pink discoloration is seen on the skin. This is the breakdown of the chromophores in the skin. It
is generally reported that large squid are more sensitive to pink coloration than
small ones (Sungsri-in 2010). As the squid grading is mostly based on colour in the
market, its transport and storage techniques should be designed to preserve the surface colour and texture. Especially the colour of the surface is important for the
squid to be marketed as a whole, and less important for the squid which to be
skinned or subjected to further processing. Freezing at sea is the recommended
processing method for the whole, frozen squid market. Immediately after capture
the squid should be placed in refrigerated seawater (RSW) at 0°C to 4 °C. The cold
seawater prevents the squid from drying out and eliminates discoloration of the skin
surface. The squid should then be quickly sorted and packed, and either blast- or
plate-frozen at −30°C to −40 °C. Rapid freezing and constant storage at low temperatures are essential to avoid changes in colour and adverse textural changes.
Fluctuating storage temperatures can also result in reddening of the product surface
which reduces market value (Learson 2000).
The quality of cephalopods changes during frozen storage. Besides protein denaturation, oil oxidation and desiccation, odour and discoloration can be seen in frozen storage. Changes in squid during frozen storage have been studied by several
researchers. It has been reported that changes in seafood meat during freezing and
frozen storage are mainly related to the modification of myofibrilar proteins and the
potential impact of lipids on protein denaturation in relation to free fatty acids
(Sikorski et al. 1976). In frozen stored squid (Illex argentinus), a significant decrease
in protein solubility was detected in 5-month storage, and then remained unchanged
during storage (Paredi et al. 2006). Similar decreases have been reported for squid
(Loligo vulgaris), octopus (Octopus vulgaris) and cuttlefish (Sepia officinalis)
3.2 Cephalopods