Emulsifying ability of porphyran prepared from dried nori, Porphyra yezoensis, a red alga.

A suspension of low-quality dried nori processed from Porphyra yezoensis, a red alga, was autoclaved at 120 degrees C for 30 min, and from the supernatant, five preparations of porphyran of differing molecular masses and chemical compositions were obtained by preprecipitation with ethanol at stepwise-increasing concentrations of 50 and 67% followed by size-exclusion chromatography. The porphyran preparations exhibited a high emulsifying activity index and high emulsion stability over a wide range of pH and temperature and also in the presence of sodium chloride. An adequately high coefficient of correlation between the median diameter of oil droplets and their 3,6-anhydrogalactose content suggests that 3,6-anhydrogalactose could take part in emulsification with porphyran.