An important and frequently observed effect of food processing is the reduction of protein nutritive quality. The simplest criterion used for the characterization of proteins is their solubility in various media. As in all legumes, the bulk of soybean proteins are globulins, characterized by their solubility in salt solutions. A series of experiments was conducted to evaluate the influence of particle size and pH on the protein solubility of soybean meal in 0.0357 M KOH solution. The obtained results revealed a negative correlation (r = -0.9218) between the protein solubility and the particle size. The soybean proteins exhibit minimum solubility at pH 4.2 to 4.5 (isoelectric region). At pH 12 when the solvent is water, soy proteins are 87% soluble.
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