Dried and toasted laver, “Yaki-nori”, Porphyra yezoensis, was compared with dried, but not toasted laver, “Hoshi-nori”, with respect to water sorption and the pigment stability during storage under various conditions.
The water-adsorbing activity of “Yaki-nori” was lower than that of “Hoshi-nori”, and hysteresis effect of the water adsorption profile was observed in “Yaki-nori”, but not in “Hoshinori”. During a three-day storage period at 20°C in 100% relative humidity, chlorophyll a was degraded mainly to chlorophyllide a and pheophorbide a in “Hoshi-nori”, but to pheophytin a in “Yaki-nori”, thus, suggesting that chlorophyllase, which hydrolyzes the chlorophyll and pheophytin to the chlorophyllide and pheophorbide respectively, was inactivated by the toasting process.
During a three-month storage period under various conditions of water activities and temperatures, chlorophyll a and carotenoids were degraded in similar profiles in “Yaki-nori”. However, the rate of pigment degradation in “Yaki-nori” depended more or less on the quality of the sample.
