Characterisation of the carotenoprotein found in carapace shells of Jasus lalandii

Carotenoprotein, containing astaxanthin as the prosthetic group was extracted from the carapace shells of the lobster, Jasus lalandii. The material, with a molecular mass of around 400 000 Da and λmax 525 nm (α-crustacyanin), was readily converted under the conditions used for extraction and on standing to the subunit (β-crustacyanin) of molecular mass around 40 000 Da and λmax 560 nm. The latter complex was stable up to 65 °C and between pH 5 and 8. Both the large molecule and the subunit showed the reversible bathochromic shift (λmax ~ 480 nm) after being subjected to conditions of heat above 65 °C and below 85 °C and pH between 3 and 10, which alter the natural protein orientation. Above 85 °C and outside of the pH range, the shift was irreversible. Crustacyanin from J. lalandii differed from the blue crustacyanin of the Homarus species with respect to visible spectra (λmax 632 nm and λmax 585 nm) and by displaying a hypsochromic shift between the α- and β-crustacyanin. Stability of the α-crustacyanin and affinity to DE52 also differed. Yellow protein, with a λmax 409/410 nm as described for the Homarus species was not detected in this J. lalandii study, although it may have been co-eluted. The properties of the extracted complex show potential for its use as a natural water soluble food colourant or temperature sensitive indicator.