24
0.005% 4-hexylresorcinol treatment for 1 min is more effective than 1.25% sulphide for longer storage times (Otwell et al. 1992). The effects of 4-hexylresorcinol
on different shrimp species Penaeus aztecus (Benner et al. 1994), Penaeus esculentus, Penaeus plebejus, Metapenaeus enchavoury and Metapenaeus benettae
(Slattery et al. 1995) were also reported.
Another reducing agent, ascorbic acid, acts as an oxygen scavenger to reduce
molecular oxygen. Inhibition mechanism of ascorbic acid is the reduction of orthoquinones to diphenols. In addition, dehydroascorbic acid is oxidized until oxidation
is delayed. Ascorbic acid is often used in combination with citric acid to produce
acidic pH (Golan-Goldhirsh and Whitaker 1984). Erythorbic acid is the stereoisomer of l-ascorbic acid and is used as an antioxidant in various processed foods
(Clark et al. 2009). Erythorbic acid is a free radical scavenger, changes the redox
potential, and reduces quinones to diphenols (Golan-Goldhirsh and Whitaker 1984).
Erythorbic acid was found to be effective in preventing the darkening of apple slices
when used with 1% citric acid (Sapers and Ziolkowski 1987). The use of erythorbic
acid with citric acid is referred to as sulphide substitution. In most studies, it is
reported that l-ascorbic acid and erythorbic acid have equal antioxidant properties
(Haard and Simpson 2000). The role of ascorbic acid and erythorbic acid in inhibiting enzymatic degradation is its ability to reduce quinones to diphenols. Hsu et al.
(1988) reported that ascorbic acid inhibits the enzyme polyphenoloxidase in the
mushrooms. Usually ascorbic acid is used in combination with other agents such as
citric acid, calcium chloride. Ascorbic acid and its isomer are the best reducing as
sulphide alternative. It is generally used as an anti-melanotic agent in fruit juices,
purees, sliced, fruits, canned fruits, and vegetables. The blackening usually proceeds after the depletion of ascorbic acid (Sapers 1993; Osuga et al. 1994; Ashie
et al. 1996a). It has been reported that the melanosis was better prevented in case of
the use of ascorbic acid in combination with other inhibitors. For example, it was
determined that the use of ascorbic acid with citric acid was more effective than the
use alone (Eskin et al. 1971; Sapers 1993). This is probably due to the stability of
ascorbic acid in the acidic environment and the inhibition effect of the acidic
medium on the catalytic activity of the enzyme. There are studies on the use of
ascorbic acid and erythorbic acid in fruits and vegetables to prevent darkening
(Ponting et al. 1972; Sapers and Ziolkowski 1987; Sapers et al. 1989, 1990; Santerre
et al. 1988; Gil et al. 1998). There has not been much study on the use of ascorbic
acid and erythorbic acid in the prevention of melanosis in shrimps. In one study, it
was determined that ascorbic acid and erythorbic acid were effective in delaying the
darkening of shrimps, especially in combination with sodium metabisulphite
(Toktas 2018; Gokoglu and Toktas 2018).
Antioxidants
Antioxidants protect the food by preventing the rancidity or colour degradation
caused by oxygen. Synthetic and natural antioxidants are used for this purpose.
Synthetic antioxidants include butylhydroxy toluene (BHT) and butylhydroxy anisole (BHA) natural antioxidants, such as tocopherols, flavonoids, cinnamic acid
2 Crustacean Shellfish
0.005% 4-hexylresorcinol treatment for 1 min is more effective than 1.25% sulphide for longer storage times (Otwell et al. 1992). The effects of 4-hexylresorcinol
on different shrimp species Penaeus aztecus (Benner et al. 1994), Penaeus esculentus, Penaeus plebejus, Metapenaeus enchavoury and Metapenaeus benettae
(Slattery et al. 1995) were also reported.
Another reducing agent, ascorbic acid, acts as an oxygen scavenger to reduce
molecular oxygen. Inhibition mechanism of ascorbic acid is the reduction of orthoquinones to diphenols. In addition, dehydroascorbic acid is oxidized until oxidation
is delayed. Ascorbic acid is often used in combination with citric acid to produce
acidic pH (Golan-Goldhirsh and Whitaker 1984). Erythorbic acid is the stereoisomer of l-ascorbic acid and is used as an antioxidant in various processed foods
(Clark et al. 2009). Erythorbic acid is a free radical scavenger, changes the redox
potential, and reduces quinones to diphenols (Golan-Goldhirsh and Whitaker 1984).
Erythorbic acid was found to be effective in preventing the darkening of apple slices
when used with 1% citric acid (Sapers and Ziolkowski 1987). The use of erythorbic
acid with citric acid is referred to as sulphide substitution. In most studies, it is
reported that l-ascorbic acid and erythorbic acid have equal antioxidant properties
(Haard and Simpson 2000). The role of ascorbic acid and erythorbic acid in inhibiting enzymatic degradation is its ability to reduce quinones to diphenols. Hsu et al.
(1988) reported that ascorbic acid inhibits the enzyme polyphenoloxidase in the
mushrooms. Usually ascorbic acid is used in combination with other agents such as
citric acid, calcium chloride. Ascorbic acid and its isomer are the best reducing as
sulphide alternative. It is generally used as an anti-melanotic agent in fruit juices,
purees, sliced, fruits, canned fruits, and vegetables. The blackening usually proceeds after the depletion of ascorbic acid (Sapers 1993; Osuga et al. 1994; Ashie
et al. 1996a). It has been reported that the melanosis was better prevented in case of
the use of ascorbic acid in combination with other inhibitors. For example, it was
determined that the use of ascorbic acid with citric acid was more effective than the
use alone (Eskin et al. 1971; Sapers 1993). This is probably due to the stability of
ascorbic acid in the acidic environment and the inhibition effect of the acidic
medium on the catalytic activity of the enzyme. There are studies on the use of
ascorbic acid and erythorbic acid in fruits and vegetables to prevent darkening
(Ponting et al. 1972; Sapers and Ziolkowski 1987; Sapers et al. 1989, 1990; Santerre
et al. 1988; Gil et al. 1998). There has not been much study on the use of ascorbic
acid and erythorbic acid in the prevention of melanosis in shrimps. In one study, it
was determined that ascorbic acid and erythorbic acid were effective in delaying the
darkening of shrimps, especially in combination with sodium metabisulphite
(Toktas 2018; Gokoglu and Toktas 2018).
Antioxidants
Antioxidants protect the food by preventing the rancidity or colour degradation
caused by oxygen. Synthetic and natural antioxidants are used for this purpose.
Synthetic antioxidants include butylhydroxy toluene (BHT) and butylhydroxy anisole (BHA) natural antioxidants, such as tocopherols, flavonoids, cinnamic acid
2 Crustacean Shellfish