RESUMEN
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 lambda(max) 525 nm (alpha-crustacyanin), was readily converted under the conditions used for extraction and on standing to the subunit (beta-crustacyanin) of molecular mass around 40,000 Da and lambda(max) 560 nm. The latter complex was stable up to 65 degrees C and between pH 5 and 8. Both the large molecule and the subunit showed the reversible bathochromic shift (lambda(max) approximately 480 nm) after being subjected to conditions of heat above 65 degrees C and below 85 degrees C and pH between 3 and 10, which alter the natural protein orientation. Above 85 degrees 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 (lambda(max) 632 nm and lambda(max) 585 nm) and by displaying a hypsochromic shift between the alpha- and beta-crustacyanin. Stability of the alpha-crustacyanin and affinity to DE52 also differed. Yellow protein, with a lambda(max) 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.