Isolation and investigation of emulsifying properties of surface-active substances from rice bran

Surface-active substances were isolated from defatted rice bran. They were 70:30 w/w ethanol/water soluble and could be further divided into n-hexane soluble fraction (fraction A) and n-hexane insoluble fraction (fraction B). For both the fractions emulsifying properties (i.e., interfacial tension, emulsion droplet diameter, emulsifying activity, and emulsion stability), were investigated and compared to those of a commercial emulsifier Atmos 150 or Tween 20. It was found that fraction A produced lower interfacial tension data and smaller droplet sizes than those of fraction B and showed, at concentrations ⩾0.7 wt%, similar emulsifying properties to those of Atmos 150. Fraction B, however, was found to have inferior emulsifying properties to those of the fraction A and Tween 20. The main substances in fraction A responsible for the emulsifying properties and mechanisms involved need to be studied.