18
factor on shelf life. Therefore, the researchers reported different shelf life for
different shrimp species. For example, at 0 °C, shelf life was reported as 6 days for
Parapenaeus. longirostris (Mendes et al. 2005), whereas it was reported to be
10 days for Macrobrachium rosenbergii (Leitao and Rios 2000) and 13–16 days for
tropical shrimps stored on ice. On the other hand, the shelf life of M. rosenbergii,
which was iced and kept at 0–4 °C, was reported as 12–16 days (Lalitha and
Surendran 2006). Abu Bakar et al. (2008) recommend that Macrobrachium rosenbergii should not be kept for more than 14 days in ice, more than 8 days at 10 °C
and more than 12 h at room temperature.
Shrimps undergo various chemical and physical changes after harvesting and
during storage. Degradation occurs by the combined action of microbial chemical
and enzymatic activities. Degradation can easily be determined by observing
changes in physical properties. Changes in colour, odour, and texture are some of
the characteristics observed in spoiled fish.
Enzymatic Spoilage
The time from shrimp death to icing is critical. Immediately after death, autolytic
and bacterial enzymes begin to break down in proteins, lipids, and carbohydrates.
Autolysis is mean the breakdown or decomposition of larger molecules such as
proteins, lipids, and carbohydrates by enzymes after the death (Wakjira 2011).
Enzymes are protein-like substances found in the flesh and stomach of shellfish
which initiate or accelerate chemical reactions. In a live organism, enzymes are in
balance via the help of. Enzymes which are kept under control by digestive or blood
systems are still active in post-mortem period and cause flavour changes before
bacterial spoilage during cold storage. Textural and appearance changes are also
seen due to enzymatic activity just after death (Gokoglu and Yerlikaya 2015).
Enzymes are the main cause of autolytic spoilage. Higher enzymatic activities
increase autolytic spoilage due to ionic strength. Enzymes and bacteria do not cause
degradation due to their natural defence systems during the life of all aquatic species. However, after harvesting, enzymes cause autolytic changes, while microorganisms on the surface of the organism enter the tissues and cause loss. After death,
the biological regulation of the enzymes is lost, and the enzymes hydrolyse muscle
proteins and resolve rigor-mortis. The digestive system of the organism, which is
overfed before death, is deteriorated very quickly because of the large number of
enzymes (Paul 2015). At harvesting, fish and shellfish contain food in their intestines and have enzymes. After the death of animals, enzymes penetrate the muscle,
weaken, and soften the meat wall (Wheaton and Lawson 1985; Hultmann 2003).
After enzymatically breakdown of proteins lipids and carbohydrates, flavour, texture, and appearance of organism change.
2 Crustacean Shellfish
factor on shelf life. Therefore, the researchers reported different shelf life for
different shrimp species. For example, at 0 °C, shelf life was reported as 6 days for
Parapenaeus. longirostris (Mendes et al. 2005), whereas it was reported to be
10 days for Macrobrachium rosenbergii (Leitao and Rios 2000) and 13–16 days for
tropical shrimps stored on ice. On the other hand, the shelf life of M. rosenbergii,
which was iced and kept at 0–4 °C, was reported as 12–16 days (Lalitha and
Surendran 2006). Abu Bakar et al. (2008) recommend that Macrobrachium rosenbergii should not be kept for more than 14 days in ice, more than 8 days at 10 °C
and more than 12 h at room temperature.
Shrimps undergo various chemical and physical changes after harvesting and
during storage. Degradation occurs by the combined action of microbial chemical
and enzymatic activities. Degradation can easily be determined by observing
changes in physical properties. Changes in colour, odour, and texture are some of
the characteristics observed in spoiled fish.
Enzymatic Spoilage
The time from shrimp death to icing is critical. Immediately after death, autolytic
and bacterial enzymes begin to break down in proteins, lipids, and carbohydrates.
Autolysis is mean the breakdown or decomposition of larger molecules such as
proteins, lipids, and carbohydrates by enzymes after the death (Wakjira 2011).
Enzymes are protein-like substances found in the flesh and stomach of shellfish
which initiate or accelerate chemical reactions. In a live organism, enzymes are in
balance via the help of. Enzymes which are kept under control by digestive or blood
systems are still active in post-mortem period and cause flavour changes before
bacterial spoilage during cold storage. Textural and appearance changes are also
seen due to enzymatic activity just after death (Gokoglu and Yerlikaya 2015).
Enzymes are the main cause of autolytic spoilage. Higher enzymatic activities
increase autolytic spoilage due to ionic strength. Enzymes and bacteria do not cause
degradation due to their natural defence systems during the life of all aquatic species. However, after harvesting, enzymes cause autolytic changes, while microorganisms on the surface of the organism enter the tissues and cause loss. After death,
the biological regulation of the enzymes is lost, and the enzymes hydrolyse muscle
proteins and resolve rigor-mortis. The digestive system of the organism, which is
overfed before death, is deteriorated very quickly because of the large number of
enzymes (Paul 2015). At harvesting, fish and shellfish contain food in their intestines and have enzymes. After the death of animals, enzymes penetrate the muscle,
weaken, and soften the meat wall (Wheaton and Lawson 1985; Hultmann 2003).
After enzymatically breakdown of proteins lipids and carbohydrates, flavour, texture, and appearance of organism change.
2 Crustacean Shellfish