On the prevention of the black spot of shrimp: I. effect of some chemical reagents on the black spot of shrimp. II. the isolation and purification of the enzyme related to the formation of black spot

On the prevention of the black spot of shrimp: I. effect of some chemical reagents on the black spot of shrimp. II. the isolation and purification of the enzyme related to the formation of black spot^*

Yasuzo Itô^**

SYNOPSIS

The causes of the black discoloration of three species of shrimp commonly caught off the coast of the State of São Paulo, Brazil, are studied and measures for its prevention are advocated.

Landings of shrimp in Santos in 1964 equaled 13% of the total landing, by weight, while economically it is the principal fishery.

I - Blackening was effectively prevented by dipping the shrimp in cooled chemical solution for 30 minutes and then storing them at low temperatures. L-ascorbic acid gave the best results, delaying discoloration up to 9 days at 0º to -2ºC and for a longer period at colder temperatures. The effect of Sodium-thiosulfate and EDTA at different temperatures is also discussed.

II - Tyrosinase was isolated and assayed by measuring the formation of Dopa-chrome from DL-Dopa at pH 6.8 an 37ºC. Tyrosinase was obtained from the shrimp liver and was purified by approximately 25 times its activity from the initial extract by absorption chromatography through Celite 545, as judged by the rate of dopachrome formation.

RESUMO

Foram estudadas, no presente trabalho, as causas do enegrecimento do camarão, tendo-se verificado que o mesmo é causado, fundamentalmente, pela ação da tirosinase, produzida no hepato pâncreas do crustáceo. O isolamento e a purificação da enzima foram realizados. A purificação foi feita, até se obter uma atividade 25 vêzes maior do que o extrato inicial, por meio de cromatografia de absorção, através de Celite 545 e avaliada através da velocidade de formação de dopacromo.

O uso de diferentes drogas também foi tratado experimentalmente, tendo-se verificado que o melhor inibidor do processo de enegrecimento é o ácido L-arcórbico que evita a formação da mancha preta durante 9 dias à temperatura de 0 a -2ºC e durante tempo mais longo em temperaturas mais baixas. Tiosulfato de sódio e EDTA também têm boa ação inibidora. As técnicas empregadas são descritas detalhadamente e é apresentada discussão com resultados obtidos por outros autores. Ao que se sabe, esta é aprimeira vez que tirosinase é isolada de um invertebrado.

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ACKNOWLEDGEMENTS

The author wishes to express his sincere thanks to Dra. M. VANNUCCI for her support and also wishes to thank Miss DULCINDA RODRIGUES DA SILVA and Mr. Luiz SANCHES for their helpful assistance.

(Received in 29/4/1966)

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*

This work was accomplished while under contract as Visiting Researcher at the Instituto Oceanográfico da Universidade de São Paulo, on a Ford Foundation Grant.

**

Present address: Hokkaido Kyoiku University, Hokkaido, Japan.

Publication Dates

• Publication in this collection
  14 June 2012
• Date of issue
  1967

History

• Received
  29 Apr 1966