Emulsifying properties of ethanol-precipitated mucilage from cellulase-hydrolyzed green algae (Monostroma nitidum)

The emulsifying properties of the ethanol-precipitated mucilage from cellul ase-hydrolyzed Monostroma nitidum were investigated. Both emulsifying activ ity and emulsion stability of the mucilage increased from 51.5 and 48.0% to 69.0 and 62.0%, respectively, and oil droplets did not coalesce when the m ucilage concentration was at 1%(w/v). Gel permeation chromatography showed that the carbohydrate moieties of the mucilage exhibited an absence of low molecular weight fractions and a broader molecular weight range for the hig h molecular weight fraction than that of the cellulase hydrolysate. Also, t here was a greater amount of high molecular weight protein-containing fract ions in the mucilage, while predominantly low molecular weight protein frac tions were in the hydrolysate. Increasing the mucilage concentration of the solution(0-20 mg/mL) led to a reduction of surface tension to 54.9 dyne/cm , and increased the emulsifying activity and emulsion stability to 76.9 and 70.0%, respectively. The oil did not separate from the emulsion when the m ucilage concentration was higher than 0.5%(w/v). When 0.2% NaCl was added t o the emulsion containing 1% mucilage. the apparent viscosity decreased fro m 37.1 to 7.6 Pa.s (x 10(-3)). Also, the emulsifying activity and emulsion stability decreased from 69.0 and 62.0% to 50.0 and 48.0%, respectively.