SALT CONCENTRATION, PH, AND FLOUR CONCENTRATION EFFECTS ON NITROGEN SOLUBILITY AND EMULSIFYING PROPERTIES OF PEANUT FLOUR

Nitrogen solubility in 2% dispersions and emulsifying properties in 8% dispersions of unheated peanut flour (50.9% protein) in water, 0.1M NaCl (low salt), and 1.0M NaCl (high salt) were measured over a pH range 2.0–10.0. Flour concentration effects were measured over the same range in water only at 2, 4, 6 and 8% flour levels (1, 2, 3, 4% protein). Both nitrogen solubility and emulsion‐forming and thickening properties of the water and low‐salt suspensions were lower at pH 4.0 than at levels below and above 4.0, increases in solubility being quite substantial below pH 3.0 and above pH 6.0. In the high‐salt suspensions, nitrogen solubility was low at pH 3.0 and below, high at pH 6.0 and above, with near linear increase between 3.0 and 6.0; no emulsions formed at pH 2.0–4.0, with generally low‐viscosity emulsions at pH 5.0–10.0. A flour concentration of 2% (1% protein) in water could support emulsion formation only at pH levels of 2, 3, 8, 9 and 10, and the quality of these emulsions was extremely poor (low viscosity); at higher flour concentrations (4, 6. 8%). emulsion capacities and viscosities were improved substantially by adjusting the pH to levels below or above 4.0, with more viscous emulsions produced below pH 4.0 than above. Multiple regression analyses confirmed that deviations of pH from 4.0 were better predictors of emulsifying properties of peanut flour than simple pH alone. Altering the electrovalent properties, ionic environment, or flour concentration strongly influenced these functional characteristics. Copyright © 1979, Wiley Blackwell. All rights reserved