21
others. PPO activity in deep water pink shrimp was found to be faster than white
shrimp and melanosis spread was slower in black tiger shrimp (Montero et al.
2001a). In a study in which the biochemical properties of the PPO enzyme were
investigated, it was determined that PPO has different molecular weight, optimum
pH, thermal stability, and kinetic parameters in different shellfish products (Nirmal
and Benjakul 2012).
Inhibition of Melanosis
Shrimps need to be processed immediately or maintained with an effective method
to maintain nutritional value, slow, or stop microbial growth, and increase shelf life.
Numerous studies have been carried out to prevent melanosis that comes at the
beginning of the factors limiting the shelf life. These studies mostly focused on the
inhibition or prevention of polyphenoloxidase activity. Various techniques and
mechanisms have been developed over many years to control undesired enzyme
activity. These techniques aim to eliminate one or more of the essential compounds
(oxygen, enzyme, copper, and substrate) in the browning reaction (Gokoglu and
Yerlikaya 2008). Before referring to the ways of prevention of melanosis, factors
affecting the development of melanosis should be known. These factors are pH of
muscle tissue, temperature, dehydration, high pressure, enzyme concentration, the
presence of oxygen, seasons, species and geographical origin of crustaceans and
technological factors (Kim et al. 2000; Mendes 2006).
Melanosis is considered a process that needs to be controlled or eliminated.
Controlling this reaction starts with a good understanding of the mechanisms of
marine products, the properties, substrates and inhibitors of the enzyme and the
chemical, biological and physical factors that affect each of them (Gonçalves and de
Oliveira 2016).
The method of catching, age and sex affects melanosis formation. Applications
during and after catching trigger a defence mechanism that activates PPO in crustaceans, resulting in increased melanosis (Bartolo and Birk 2002; McEvily et al. 1991).
Melanosis Inhibition Methods
1. Chilling
Cooling temperatures slow the enzyme activity. Enzymatic reactions can be controlled by temperature. Every 10 °C increase in temperature increases the reaction. Conversely, a reduction of 10 °C also slows down the biological activity.
Due to the close relationship between deterioration and storage temperature,
crustacean products should be rapidly cooled immediately after harvesting
(Pardio et al. 2011). Melanosis is slowed down by ice cooling but cannot be
completely prevented (Martínez-Alvarez et al. 2007).
2. Heating
Heating is one of the most common methods applied to foods to destroy microorganisms and inactivate enzymes. The thermal stability of polyphenoloxidase
varies according to the source of the enzyme. Its catalytic activity is generally
2.1 Shrimps/Prawns
others. PPO activity in deep water pink shrimp was found to be faster than white
shrimp and melanosis spread was slower in black tiger shrimp (Montero et al.
2001a). In a study in which the biochemical properties of the PPO enzyme were
investigated, it was determined that PPO has different molecular weight, optimum
pH, thermal stability, and kinetic parameters in different shellfish products (Nirmal
and Benjakul 2012).
Inhibition of Melanosis
Shrimps need to be processed immediately or maintained with an effective method
to maintain nutritional value, slow, or stop microbial growth, and increase shelf life.
Numerous studies have been carried out to prevent melanosis that comes at the
beginning of the factors limiting the shelf life. These studies mostly focused on the
inhibition or prevention of polyphenoloxidase activity. Various techniques and
mechanisms have been developed over many years to control undesired enzyme
activity. These techniques aim to eliminate one or more of the essential compounds
(oxygen, enzyme, copper, and substrate) in the browning reaction (Gokoglu and
Yerlikaya 2008). Before referring to the ways of prevention of melanosis, factors
affecting the development of melanosis should be known. These factors are pH of
muscle tissue, temperature, dehydration, high pressure, enzyme concentration, the
presence of oxygen, seasons, species and geographical origin of crustaceans and
technological factors (Kim et al. 2000; Mendes 2006).
Melanosis is considered a process that needs to be controlled or eliminated.
Controlling this reaction starts with a good understanding of the mechanisms of
marine products, the properties, substrates and inhibitors of the enzyme and the
chemical, biological and physical factors that affect each of them (Gonçalves and de
Oliveira 2016).
The method of catching, age and sex affects melanosis formation. Applications
during and after catching trigger a defence mechanism that activates PPO in crustaceans, resulting in increased melanosis (Bartolo and Birk 2002; McEvily et al. 1991).
Melanosis Inhibition Methods
1. Chilling
Cooling temperatures slow the enzyme activity. Enzymatic reactions can be controlled by temperature. Every 10 °C increase in temperature increases the reaction. Conversely, a reduction of 10 °C also slows down the biological activity.
Due to the close relationship between deterioration and storage temperature,
crustacean products should be rapidly cooled immediately after harvesting
(Pardio et al. 2011). Melanosis is slowed down by ice cooling but cannot be
completely prevented (Martínez-Alvarez et al. 2007).
2. Heating
Heating is one of the most common methods applied to foods to destroy microorganisms and inactivate enzymes. The thermal stability of polyphenoloxidase
varies according to the source of the enzyme. Its catalytic activity is generally
2.1 Shrimps/Prawns