40
Some carboxylic acids and their salts have been treated. Dipping into sodium
propionate and sodium acetate solutions before chilling of shrimp (Penaeus monodon) was found effective to extend shelf life compared to untreated control samples (Tam et al. 2018).
Essential oils (EOs) are natural antimicrobial in food preservation. They are volatile liquids extracted from plant material and contain antimicrobial compounds.
They are commonly used to protect the quality of foods due to their antimicrobial
properties. Shrimp (Penaeus monodon) was dipped into essential oils (cinnamon
oil, garlic oil and lime oil) and organic acids (lactic acid, tartaric acid, and sodium
diacetate) at 1:2 shrimp/treatment rates for 30 min. According to microbiological
and physicochemical analyses essential oils and organic acid treatments were successful to extend the shelf life. Mixtures of tartaric acid and garlic oil and lactic acid
and cinnamon oil were the best effective treatments to delay the spoilage of fresh
shrimps (Noordin et al. 2018).
Ozone has been used for many food products to reduce the microbial load. Ozone
destroys algae, viruses, bacteria, and fungi on contact. The biocidal effect of ozone
is caused by its high oxidation potential, reacting with organic material up to 3000
times faster than chlorine. Washing with ozonated water of shrimps reduced the
number of bacteria and improved microbial quality during cold storage (Tantratian
et al. 2011). Quality attributes of sequential minimal ozone-treated ice stored shrimp
(Litopenaeus vannamei) were investigated. Minimal ozone treatment sequentially
applied at days 1, 3, 5, 8 and 11. Sequential minimal ozone treatment affected
colour, titratable acidity, total volatile bases, trimethylamine, peroxide and para
anisidine values of ice stored shrimp. After minimal ozone treatment, aerobic plate
counts significantly decreased. During iced storage shrimps showed lower microbial count compared to control (Okpala 2014a, 2015). In another study, Okpala
(2014b) reported that sequential minimal ozone treatment affected some physicochemical properties of Pacific white shrimp (Litopenaeus vannamei) during iced
storage. Increasing ozone exposures and iced storage changed proximate composition, colour, and textural properties of Pacific white shrimp (Litopenaeus vannamei)
(Okpala 2017).
Quality Changes of Chilled Shrimps
Chemical and biochemical reactions responsible for quality loss during cold storage
can be slowed and shelf life can be increased (Lalitha and Surendran 2006).
However, shrimps stored in cold loss their quality after a period due to microbial
growth. There is an increase in the number of microorganism (especially psychrotrophic and psychrofilic) in the cold during storage. Jeyasekaran et al. (2006)
reported that in white shrimps (Penaeus indicus) stored in ice, the total bacterial
count increased from 10
6
to 10
9
cfu/g at 24 h, and total psychophilic bacteria
increased from 10
3
to 10
6
cfu/g. Huang et al. (1996) found that the number of psychrotrophic bacteria which initially is 3.86 log cfu/g, reached 9.46 log cfu/day on
the tenth day of chilled storage in the fresh shrimps (Penaeus spp.). Erdem and
2 Crustacean Shellfish
Some carboxylic acids and their salts have been treated. Dipping into sodium
propionate and sodium acetate solutions before chilling of shrimp (Penaeus monodon) was found effective to extend shelf life compared to untreated control samples (Tam et al. 2018).
Essential oils (EOs) are natural antimicrobial in food preservation. They are volatile liquids extracted from plant material and contain antimicrobial compounds.
They are commonly used to protect the quality of foods due to their antimicrobial
properties. Shrimp (Penaeus monodon) was dipped into essential oils (cinnamon
oil, garlic oil and lime oil) and organic acids (lactic acid, tartaric acid, and sodium
diacetate) at 1:2 shrimp/treatment rates for 30 min. According to microbiological
and physicochemical analyses essential oils and organic acid treatments were successful to extend the shelf life. Mixtures of tartaric acid and garlic oil and lactic acid
and cinnamon oil were the best effective treatments to delay the spoilage of fresh
shrimps (Noordin et al. 2018).
Ozone has been used for many food products to reduce the microbial load. Ozone
destroys algae, viruses, bacteria, and fungi on contact. The biocidal effect of ozone
is caused by its high oxidation potential, reacting with organic material up to 3000
times faster than chlorine. Washing with ozonated water of shrimps reduced the
number of bacteria and improved microbial quality during cold storage (Tantratian
et al. 2011). Quality attributes of sequential minimal ozone-treated ice stored shrimp
(Litopenaeus vannamei) were investigated. Minimal ozone treatment sequentially
applied at days 1, 3, 5, 8 and 11. Sequential minimal ozone treatment affected
colour, titratable acidity, total volatile bases, trimethylamine, peroxide and para
anisidine values of ice stored shrimp. After minimal ozone treatment, aerobic plate
counts significantly decreased. During iced storage shrimps showed lower microbial count compared to control (Okpala 2014a, 2015). In another study, Okpala
(2014b) reported that sequential minimal ozone treatment affected some physicochemical properties of Pacific white shrimp (Litopenaeus vannamei) during iced
storage. Increasing ozone exposures and iced storage changed proximate composition, colour, and textural properties of Pacific white shrimp (Litopenaeus vannamei)
(Okpala 2017).
Quality Changes of Chilled Shrimps
Chemical and biochemical reactions responsible for quality loss during cold storage
can be slowed and shelf life can be increased (Lalitha and Surendran 2006).
However, shrimps stored in cold loss their quality after a period due to microbial
growth. There is an increase in the number of microorganism (especially psychrotrophic and psychrofilic) in the cold during storage. Jeyasekaran et al. (2006)
reported that in white shrimps (Penaeus indicus) stored in ice, the total bacterial
count increased from 10
6
to 10
9
cfu/g at 24 h, and total psychophilic bacteria
increased from 10
3
to 10
6
cfu/g. Huang et al. (1996) found that the number of psychrotrophic bacteria which initially is 3.86 log cfu/g, reached 9.46 log cfu/day on
the tenth day of chilled storage in the fresh shrimps (Penaeus spp.). Erdem and
2 Crustacean Shellfish