INFLUENCE OF PH AND SALT CONCENTRATION ON NITROGEN SOLUBILITY AND EMULSIFICATION PROPERTIES OF SOY FLOUR

Nitrogen solubility and emulsifying properties of soy flour were measured over a pH range of 20–10.0 and in three dispersion media including water, 0.1M NaCl (low salt) and 1.0M NaCl (high salt). Nitrogen solubility and emulsion capacity of water and low‐salt suspensions were similar and were quite low at pH 4.0 but improved significantly at pH levels below or above 4.0. In high‐salt suspensions, nitrogen solubility and emulsion capacity generally increased from IJH 2.0 to PH 10.0. Whereas no emulsions were formed by water ‐and low‐salt suspensions at pH 4.0, thick mayonnaise‐like emulsions were formed by the high salt treatment at this pH. Except for the water and low‐salt suspensions at pH 4.0 and the low‐salt suspension at pH 5.0, all emulsions formed were mayonnaise‐like in consistency and compared favorably to a commercial mayonnaise. Multiple regression analyses showed that pH was the primary determinant of nitrogen solubility and emulsifying properties of soy flour. The influence of soluble nitrogen on emulsion capacity and viscosity was difficult to discern since it too was strongly influenced and confounded by pH effects. Changing the electrovalent properties of the protein, either by shifts in pH or by modifications in salt concentration, appeared to be the most significant factor influencing these functional characteristics. Copyright © 1979, Wiley Blackwell. All rights reserved