Cyclooxygenase activity: Bis-oxygenation and cyclization of arachidonic acid to Prostaglandin $G_2$ ($PGG_2$).
Peroxidase activity: Reduction of $PGG_2$ to Prostaglandin $H_2$ ($PGH_2$), which is then converted by tissue isomerases into prostaglandins ($PGE_2, PGF_{2\alpha}, PGD_2$), prostacyclins, and thromboxanes.
Correct Option: Option 1 (Cyclooxygenases).
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12
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
The antioxidants a-tocopherol and astaxanthin act by one of the following mechanisms
Antioxidant Action of $\alpha$-Tocopherol and Astaxanthin:
$\alpha$-Tocopherol (Vitamin E) and Astaxanthin (a red keto-carotenoid) act as chain-breaking biological antioxidants in fatty fishes and crustaceans.
Mechanism: They neutralize lipid peroxidation by directly scavenging reactive oxygen species (ROS) and reactive oxygen intermediates (ROM), donating phenolic hydrogen atoms to convert lipid peroxyl radicals ($LOO^\bullet$) into stable hydroperoxides and quenching excited singlet oxygen ($^1O_2$).
Correct Option: Option 2 (Scavenging reactive ROS and ROM species).
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13
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
In fishes, Vitamin D is predominantly present in the form of Cholecalciferol (Vitamin $D_3$).
Fatty fish species (salmon, mackerel, sardines) and fish liver oils accumulate substantial amounts of cholecalciferol synthesized endogenously or obtained via the marine planktonic food web.
Ergocalciferol (Vitamin $D_2$) is the plant/fungal provitamin form.
Correct Option: Option 2 (Cholecalciferol).
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14
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
The process of refining the fish body oil to remove the phospholipids is
Degumming: The initial refining unit operation applied to crude fish body oil to remove non-glyceride impurities, specifically hydratable and non-hydratable phospholipids (gums).
Involves heating the crude oil with hot water or dilute phosphoric acid ($0.1-0.2\%$) to hydrate the phospholipids into insoluble sludges that are removed by centrifugation.
Correct Option: Option 1 (Degumming).
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15
ICAR JRF Fish Processing Technology 29 Jun 2024Shift 1
MCQ (Single Correct)+4−1
The bleeding of fish contributes to one of the following phenomena in fish.
Hemeproteins as Pro-oxidants: Fish blood contains high concentrations of hemoglobin and myoglobin, which possess iron-containing heme prosthetic groups ($Fe^{2+}/Fe^{3+}$). Free heme and iron are among the most potent catalysts of lipid peroxidation in unsaturated fatty acids.
Benefits of Bleeding (Exsanguination): Immediate bleeding of fish on board (by severing gill arches or caudal peduncle) expels blood from the muscle vascular bed, substantially reducing hemeprotein-induced lipid oxidation, delaying rancidity, and preventing dark, bruised muscle discolorations.
Correct Option: Option 1 (Reduces oxidation due to the removal of hemeprotein).
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