Measurement of Emulsifying Properties with Small Quantities of Soybean Protein by a Sonicator and Turbidimetry

Abstract

Emulsifying properties of a soybean protein(acid-precipitated protein)were measured with small quantities of the protein(about 10mg)by emulsification with a sonicator followed by tubidimetry with a photometer. Recommended conditions for measurment were as follows. Protein solution(1%, 1.4ml)and oil(0.6ml)were emulsified with the sonicator(20KHz)at 60 W for 3 minutes. The turbidity of this emulsion was measured at 500nm after the dilution to 2500 folds. This turbidity was closely related to the emulsion stability determined by measurement of water content in the low part of the emulsion after keeping it for 24 hours. The degree of flocculation was determined from the difference of turbidity between with and without a detergent(SDS)in a diluting solution for the emulsion.