Natural occurrence of denatured phycoerythrin during Porphyra cultivation

Abstract

Dried Nori (Porphyra spp.) normally turns greenish when toasted and this color usually remains for many days when moistened with vinegar in the Japanese food ‘Sushi’. However, for some lots of toasted Nori, this color changes to an undesirable reddish-brown one within a few hours in vinegar. A clear difference was noticed by spectrophotometry between the abnormally and normally colored toasted Nori. The former exhibited absorption maxima at around 490 and 530–600 nm while these were absent in the spectrum of the latter. The responsible pigment for the abnormal coloration was purified by ammonium sulfate fractionation and preparative flat-bed isoelectric focusing. On the basis of pI, molecular weight and the visible absorption, fluorescence and circular dichroism spectra, the pigment was identified as monomeric phycoerythrin. Dried Nori contained three times as much monomer as hexamer. From field cultivation tests, dried Nori produced large amounts of monomeric phycoerythrin when the fronds on frozen nursery-nets were damaged.