139
activity. In studies, lipid levels of Mytilus platensis, Mytilus galloprovincialis (De
Moreno et al. 1980), Perna perna (Narváez et al. 2008) and Mytilus edulis (Dare and
Edwards 1975; Zandee et al. 1980) significantly decreased with spawning.
Lipid classes found in mussel oil have been reported to include sterol esters, triglycerides, free fatty acids (saturated and unsaturated), carotenoids, sterols, and
polar lipids (Sukumaran et al. 2010).
3.1.1.2 Postharvest Quality Changes in Mussels
Microorganisms play an important role in the degradation of seafood. Bivalve molluscs are filter-feeding organisms, and they can accumulate pathogenic bacteria and
viruses. Contamination of seafood by microorganisms can be at various stages such
as processing, storage, and distribution. Water, facilities, equipment, and personnel
are sources of contamination. The processing step is particularly important due to
the potential high microbial load on the surface. The number of microorganisms
present in the product determines whether the contamination can cause microbial
degradation or disease from seawater (Odeyemi et al. 2018).
The quality of seafood depends on the characteristics of the individual (such as
species, sex and age), external factors (such as the region, food and water quality,
temperature and salinity) and post-harvest variable factors (harvesting method,
transport and storage). Season is an effective factor on the quality of bivalves. The
chemical composition of bivalves may change with the season. Especially the reproductive cycle is an important factor in this. They are in the waiting phase where they
use their stored energy in winter. They use the energy they have stored as glycogen
for both live and gametogenesis. Since gonads develop in this phase, there is an
energy requirement for the gametes. When the spawning season starts, the glycogen
content is usually minimum in winter and maximum in autumn (Gosling 2015).
Information on the effect of seasonal variation on chemical composition is given
above in the section “Nutritive composition of bivalves”. This change significantly
affects the quality of the mussel.
Despite the change in environmental factors, a reaction called stress occurs in the
living. Stress disrupts the physiological balance of the organism. Bivalves react to
this stress differently. For example, mussels close their valves in the case of stress
and oxygen intake decreases. Such variability will condition both the handling and
storage of bivalves. Therefore, it is very important to understand the results of the
stress. Depending on the degree and the duration of the stress period, the animal will
become more fragile and therefore there will be occurred differences in metabolism,
by decreasing the quality of the bivalve. Thus, stress negatively affects the final
quality of seafood, which causes negative consequences for the industry. Glycogen
is reported as an indicator of stress in fish as its content decreases with increasing
stress (Lopes Da Costa 2018).
The fishing and harvesting methods of bivalves are an effective factor on the
product quality. The methods vary according to the type of bivalve and the environment in which the bivalve lives. Among the methods, catching by hand causes the
3.1 Bivalves
activity. In studies, lipid levels of Mytilus platensis, Mytilus galloprovincialis (De
Moreno et al. 1980), Perna perna (Narváez et al. 2008) and Mytilus edulis (Dare and
Edwards 1975; Zandee et al. 1980) significantly decreased with spawning.
Lipid classes found in mussel oil have been reported to include sterol esters, triglycerides, free fatty acids (saturated and unsaturated), carotenoids, sterols, and
polar lipids (Sukumaran et al. 2010).
3.1.1.2 Postharvest Quality Changes in Mussels
Microorganisms play an important role in the degradation of seafood. Bivalve molluscs are filter-feeding organisms, and they can accumulate pathogenic bacteria and
viruses. Contamination of seafood by microorganisms can be at various stages such
as processing, storage, and distribution. Water, facilities, equipment, and personnel
are sources of contamination. The processing step is particularly important due to
the potential high microbial load on the surface. The number of microorganisms
present in the product determines whether the contamination can cause microbial
degradation or disease from seawater (Odeyemi et al. 2018).
The quality of seafood depends on the characteristics of the individual (such as
species, sex and age), external factors (such as the region, food and water quality,
temperature and salinity) and post-harvest variable factors (harvesting method,
transport and storage). Season is an effective factor on the quality of bivalves. The
chemical composition of bivalves may change with the season. Especially the reproductive cycle is an important factor in this. They are in the waiting phase where they
use their stored energy in winter. They use the energy they have stored as glycogen
for both live and gametogenesis. Since gonads develop in this phase, there is an
energy requirement for the gametes. When the spawning season starts, the glycogen
content is usually minimum in winter and maximum in autumn (Gosling 2015).
Information on the effect of seasonal variation on chemical composition is given
above in the section “Nutritive composition of bivalves”. This change significantly
affects the quality of the mussel.
Despite the change in environmental factors, a reaction called stress occurs in the
living. Stress disrupts the physiological balance of the organism. Bivalves react to
this stress differently. For example, mussels close their valves in the case of stress
and oxygen intake decreases. Such variability will condition both the handling and
storage of bivalves. Therefore, it is very important to understand the results of the
stress. Depending on the degree and the duration of the stress period, the animal will
become more fragile and therefore there will be occurred differences in metabolism,
by decreasing the quality of the bivalve. Thus, stress negatively affects the final
quality of seafood, which causes negative consequences for the industry. Glycogen
is reported as an indicator of stress in fish as its content decreases with increasing
stress (Lopes Da Costa 2018).
The fishing and harvesting methods of bivalves are an effective factor on the
product quality. The methods vary according to the type of bivalve and the environment in which the bivalve lives. Among the methods, catching by hand causes the
3.1 Bivalves