Shrimp preservation

Frozen raw breaded shrimp preservative sufficient to retard develop-... 

As is the case with sorbic acid, benzoic acid penetrates the cell wall in the undissociated form. As a consequence, it is active at lower pH values only (pKa at 25°C = 4.19) and therefore serves as a preservative for sour products such as fruit juices and jams. In shrimp preservation it is applied as a powder that is spread over the shrimps, passes cell walls, and then ionizes in the intracellular fluid to yield protons that acidify the alkaline interior of the cell. The main cause of its activity, however, is biochemical effects (Eklund, 1980) such as inhibition of oxidative phosphorylation and of enzymes from the citric acid cycle (Chipley, 1983). In mayonnaise preserved by benzoic acid, the undissociated acid is mainly present in the lipid phase, which can be considered as a reservoir for the aqueous phase. 

Irradiation of commercial shrimp in which melanogenesis had begun accelerated the reaction. It was postulated that the quinone-like end products of the reaction sequence acted as competitive inhibitors for the reaction and also functioned as radiation protectors for the enzyme. Subsequent irradiation would destroy the capacity of the end products to inhibit the reaction and simultaneously preserve the enzyme activity, thus accelerating further melanogenesis. 

The tentative levels of irradiation for the successful preservation of shrimp and oysters now recommended are summarized in Table IX. 

The gut bubbles in adult brine shrimp did appear, however, to form from gas nuclei (ref. 419) these presumably were incidentally ingested by the animals during filter feeding. Thus a slow compression schedule increased the number of bubbles by apparently preserving nuclei during compression to the equilibration pressure. At each pressure level, gas could diffuse into the gas nuclei, tending to stabilize them against collapse when further compressed. Prepressurization had the opposite effect, as it would tend to reduce the number of bubbles as a result of presumed dissolution of many gas nuclei (ref. 419 see also Sections 1.3.1 and 1.4.3). 

Tsai, G.J., Su, W.-H., Chen, H.C., and Pan, C.-L. 2002. Antimicrobial activity of shrimp chitin and chitosan from different treatments and applications of fish preservation. Fisheries Sci. 68, 170-177. 

Formerly shrimps were put up in bulk with a preservative. These were headless (only the head and thorax removed, the shell left on), and since that method of preservation is no longer approved, very few shrimps are obtained upon the market other than canned. Some pickled headless shrimps are put up in 1 to 6 gallon cans for hotels. These are boiled in strong brine for several minutes and put up in a saturated salt solution. They keep, but are very salty, and as it takes... 

Products and Uses A preservative that prevents discoloration of dried fruit, fresh shrimp, dried, fried, frozen potatoes, and prevents bacterial growth in wine. 

Fagbenro, O. A. 1996. Preparation, properties and preservation of lactic acid fermented shrimp heads. Food Res. Int. 29 595-599. 

Shrimps are marketed soon after catch as live, fresh with shell, with or without head, cooked in brine, or cooked without shell. They have very short shelf lives. Shrimps are also sold canned, deep frozen or as an extract or a salad ingredient. Canned shrimps are heated (pasteurized) at just 80-90 °C so as not to affect their flavor hence, they are semi-preserves with a limited shelf life. 

Erythorbic acid and sodium erythorbate may be used for preserved and semi-preserved fish products and frozen and deep-frozen fish at a concentration of 1500 mg/kg. The amount of these antioxidants allowed for preservation of cured and preserved meat products is only 500 mg/kg (expressed as erythorbic acid). The use of 4-hexylresorcinol (4-hexyl-1,3-benzenediol) is permitted up to 2 mg/kg as a colour retention agent for treatment of crustacean meat (fresh and frozen), namely to prevent black spots arising by enzymatic browning reactions, known as shrimp melanosis. 

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