31
when indole level was over 250 μg/kg (Food and Drug Administration (FDA) 1982;
Mendes et al. 2005). Lower indole levels in deep water pink shrimp (Parapenaeus
longirostris) were found at low temperature compared to higher storage temperatures. It is determined that high temperature accelerated indole formation (Mendes
et al. 2005). Similar results were obtained with Penaeus merguiensis by Shamshad
et al. (1990). Indole has been reported as the best chemical indicator to confirm
chemical degradation in shrimps (Tripathy 2013). It is reported that indole test is
used to determine if raw shrimp is exposed to high temperature because storage
temperature is taken into consideration rather than storage time for indole formation
(Botta 1995). The amount of indole formed in shrimps depends on the temperature
and processing and storage applications and bacterial population. In a study on the
effect of temperature on the level of indole, it was found that indole may be a good
indicator for shrimp stored at high temperature and handled in poor hygienic the
conditions (Mendes et al. 2000).
Oxidative Spoilage
Fat ratio in shrimp is quite low compared to other aquatic products. Although their
low-fat content, shrimps are susceptible to oil oxidation during storage because
their lipids contain high levels of polyunsaturated fatty acids. Oksuz et al. (2009)
have determined the average total lipid ratio in deep water pink shrimp (P. longirostris) to be 1.1% and the ratio of polyunsaturated fatty acids in total fatty acids to be
42.13%. Li et al. (2011) reported that the rate of polyunsaturated fatty acids varied
between 32.8 and 47.5% in seven shrimp species. Oxidation causes physiochemical
and taste changes in shrimp. Since the shrimp has low fat content, fat oxidation is
more important in frozen products (Bak et al. 1999; Tsironi et al. 2009).
The peroxide value (PV) of the pacific white shrimp (L. vannamei) stored in ice
exceeded the limit value after 8 days. Para anisidine value (pAV) which indicates
secondary lipid oxidation products in seafood reached to 224.04 value at 12 day in
these shrimp samples (Okpala et al. 2014).
Sensorial Spoilage
Degradation is a phenomenon that can be detected by smell, taste, touch, and sight.
These changes detected by our sensory organs are caused by the effects of microbial, chemical, and enzymatic activities. The chemical compounds which formed
from the metabolism of spoilage microorganisms produce unacceptable flavours
and odours associated with sensory spoilage. Progression of lipid oxidation leads to
undesirable odour and taste formation.
It is reported that shrimp freshness can be determined by measuring the changes
in sensory properties such as appearance, odour, colour, and texture. Changes in
these attributes can be measured by sensory or instrumental methods (Olafsdottir
2.1 Shrimps/Prawns
when indole level was over 250 μg/kg (Food and Drug Administration (FDA) 1982;
Mendes et al. 2005). Lower indole levels in deep water pink shrimp (Parapenaeus
longirostris) were found at low temperature compared to higher storage temperatures. It is determined that high temperature accelerated indole formation (Mendes
et al. 2005). Similar results were obtained with Penaeus merguiensis by Shamshad
et al. (1990). Indole has been reported as the best chemical indicator to confirm
chemical degradation in shrimps (Tripathy 2013). It is reported that indole test is
used to determine if raw shrimp is exposed to high temperature because storage
temperature is taken into consideration rather than storage time for indole formation
(Botta 1995). The amount of indole formed in shrimps depends on the temperature
and processing and storage applications and bacterial population. In a study on the
effect of temperature on the level of indole, it was found that indole may be a good
indicator for shrimp stored at high temperature and handled in poor hygienic the
conditions (Mendes et al. 2000).
Oxidative Spoilage
Fat ratio in shrimp is quite low compared to other aquatic products. Although their
low-fat content, shrimps are susceptible to oil oxidation during storage because
their lipids contain high levels of polyunsaturated fatty acids. Oksuz et al. (2009)
have determined the average total lipid ratio in deep water pink shrimp (P. longirostris) to be 1.1% and the ratio of polyunsaturated fatty acids in total fatty acids to be
42.13%. Li et al. (2011) reported that the rate of polyunsaturated fatty acids varied
between 32.8 and 47.5% in seven shrimp species. Oxidation causes physiochemical
and taste changes in shrimp. Since the shrimp has low fat content, fat oxidation is
more important in frozen products (Bak et al. 1999; Tsironi et al. 2009).
The peroxide value (PV) of the pacific white shrimp (L. vannamei) stored in ice
exceeded the limit value after 8 days. Para anisidine value (pAV) which indicates
secondary lipid oxidation products in seafood reached to 224.04 value at 12 day in
these shrimp samples (Okpala et al. 2014).
Sensorial Spoilage
Degradation is a phenomenon that can be detected by smell, taste, touch, and sight.
These changes detected by our sensory organs are caused by the effects of microbial, chemical, and enzymatic activities. The chemical compounds which formed
from the metabolism of spoilage microorganisms produce unacceptable flavours
and odours associated with sensory spoilage. Progression of lipid oxidation leads to
undesirable odour and taste formation.
It is reported that shrimp freshness can be determined by measuring the changes
in sensory properties such as appearance, odour, colour, and texture. Changes in
these attributes can be measured by sensory or instrumental methods (Olafsdottir
2.1 Shrimps/Prawns