Comparative analysis on the biochemical properties of phenoloxidase isolated from Euphausia superba and Trachypenaeus curvirostris

Abstract:

Melanosis is a prominent problem in the transportation and storage of Antarctic krill. In order to explore the similarities and differences in the process of melanosis between Antarctic krill and common sea shrimps, Euphausia superba and Trachypenaeus curvirostris were selected as research objects. A sensory evaluation of the melanosis process of the two shrimps during storage at (2±1)℃ were observed. The phenoloxidase (PO) was extracted and purified from the two species, the biochemical properties of which were further examined and compared. The results showed that the black spot formation was more serious in Antarctic krill under cold conditions at 24 h, and large areas of black spots were concentrated in the cephalothorax, abdominal shell, and tail of Antarctic krill. For T. curvirostris, slight black spots were observed in the cephalothorax and tail after 72 h, and then gradually spread to the whole body. The crude PO solutions of the two shrimp species were purified using ammonium sulfate and filtered through Sephadex G-100 gel. The purification fold of the PO solutions of T. curvirostris and E. superba reached 17.22 and 19.67, respectively. The optimum PO temperature was 30℃ for E. superba and 40℃ for T. curvirostris, respectively. The PO activity of Antarctic krill was higher at low temperatures and that of sea catch shrimp was higher at high temperatures. The optimum pH was between 6.0 and 7.0 for both species. Sodium metabisulfite, sodium bisulfite, 4-HR, L-cysteine, and ascorbic acid can all effectively inhibit the PO activity of the two shrimp species. Among these chemical reagents, 4-HR showed the best inhibitory effect on PO activity. The findings in this paper may provide a basis for the quality control during cold chain logistics of Antarctic krill, and also provide a reference for effectively suppressing melanosis in shrimps after death.