Phenol Oxidase in Shrimp and Crab

Abstract

The major difficulty encountered in the purification of phenolases is the relatively small quantities of active material present in comparison to totai inactive components. The best source of phenolases appears to be mushroom (Psalliotes canzpestris) where only 5 to 10 mg of enzyme per lb of wet material has been found (II), and enzyme from this source has considerably greater activity than shrimp enzyme(s) .In an effort to locate the area in shrimp and the specie of shrimp containing the highest concentration of phenolase, a study was made of enzyme activities of various anatomical areas of different species of shrimp including antennae, abdominal shell, press juice from various areas of the cephalothorax and blood. Thorough studies were made of phenolase activities in blood samples from Pertaeus aztecus, Penaeus setiferus, and the blue crab (Callinectes sapidus). Experiments were also carried out to determine natural substrates involved in shrimp melanosis and effects of certain oxidative inhibitors on the catecholase activity of shrimp protein. MATERIALS AND METHODSA. Shrimp samples analyzed. The P. setiferus exoskeletons, taken from freshly caught shrimp, were frozen until analyzed for phenolase activity. The Penaezcs duorarum exoskeletons were taken from shrimp that had been refrigerated in ice approximately one week prior to analysis. The exoskeletons were taken from the abdomen of shrimp and included the thin pellicle which separates the epidermis from the remainder of the shell.Juice was pressed from fresh P. aztecw and P. setiferzls heads, centrifuged (4,500 x g, 10 min) and frozen until analyzed. Blood samples were obtained by aspirating blood from the pericardial sinuses of live shrimp or immediately following their death. If freshly caught shrimp are chilled to approximately' 1.5" C immediately after death, their blood remains uncoagulated for 1 hr or more. Blood samples were collected from shrimp of different catches by inserting a No 20 hypodermic needle through the thin membrane which separates the carapace from the abdomen, into the pericardial area and aspirating the blood into small polyethylene bottles.Some of these blood samples were treated with various antioxidants and anticoagulants and centrifuged to separate the corpuscles from the plasma. Other samples were centrifuged after the blood had coagulated. The various samples were then fractionated as described in the results and analyzed for phenolase activity (3). B. Preparation of crab blood samples. Large crabs (c. sapidkks) were kept at 4" C for 1 hr and blood removed by severing one or two crawling legs between the first and second joints. The colorless blood was collected in a cold polyethylene beaker and stirred to remove fibrinogen.This blood turned light blue upon exposure to air as a result of oxidation of the hemocyanin.It was then centrifuged (27,000x g, 20 min) to remove residual clot and cells.A 50-ml aliquot of the serum was used to further purify hemocyanin. It was chilled to 0" C and cold 5% acetic slowly added until a slight...

Purification and Characterization of Phenoloxidase Isoforms From Taiwanese Black Tiger Shrimp (Penaeus Monodon)

“…A lag or induction period of approximately 2.5 h was observed prior to the onset of the hydroxylation. This lag allows the enzyme to build up sufficient o-diphenol to allow the reaction to proceed (Bailey et al 1960;Whitaker 1972). Maximal hydroxylation of both tyramine and tyrosine was observed during the third and fourth hours of the incubation period (Fig.…”

Effect of modified ice storage on the quality and prevention of darkening discoloration of shrimp Solenccera prominentis.

“…The darkening discoloration of shrimp during storage is considered to be caused by an enzymatic reaction in which tyrosine or tyrosine-like compounds are oxidized in the presence of polyphenol oxidase and oxygen, to produce a dark pigment melanin.1-5) So far, much efforts have been made to prevent the development of darkening discoloration. [6][7][8][9][10][11][12][13][14][15] Although controlling pH and immersing in water to exclude oxygen were effective in inhibiting the darkening discoloration,2,3,5,9,16) some physical changes such as loss in natural luster and softening in texture were observed during storage.12) Cysteine,9) aluminium compounds and ethylenediamine-tetraacetic acid (EDTA)5) showed good inhibitory effects on the development of darkening discoloration of shrimp, but it is not commercially used yet due to the cost and limitation of dosage. Other than removing heads, washing and immediate chilling, the use of sulfite agents (potassium bisulfite, etc.)…”

Antioxidants versus Food Antioxidant Additives and Food Preservatives

“…Another example of precaution advice is related to sodium metabisulfite (labeled as E223; Table 1), or other additives in shrimps, prawns or similar animals (even if directly frozen). The “head” of prawns quickly becomes dark (browning) due to polyphenol oxidase-induced melanosis [23,24], and producers know that consumers prefer that these crustaceans keep the red color. Though sucking fresh crustaceans is pleasant to many and safe, if the product has been hypothetically treated with unknown quantities of additives, such as sodium metabisulfite, a similar action could be neither tasty nor completely safe (if the dose is high or a high number of pieces are consumed).…”