Rice endosperm proteins are quite insoluble and have low commercial value mainly due to their poor functional properties. In this study the influence of enzymatic hydrolysis and tangential flow ultrafiltration were evaluated in obtaining a hydrolyzed rice endosperm protein of high solubility and reduced sodium content. Initially, enzymatic hydrolysis kinetics was evaluated to select the enzyme/substrate ratio and hydrolysis time appropriate to the process. The rice endosperm proteins were extracted by the alkaline method and hydrolyzed with Alcalase (R) until reaching degree of hydrolysis of 9.40% when 40% of the protein became solubilized. The molar masses of the soluble peptides were evaluated via LC-MS QTOF MS/MS. The hydrolyzed soluble fraction was recovered by centrifugation, pre-treated by microfiltration and then concentrated by tangential flow ultrafiltration using a 1 kDa membrane. The sample was subjected to two diafiltrations with reduced solvent volume, after it was dried and analyzed with respect to their protein, mineral, sodium and potassium contents, solubility and foaming properties. The hydrolyzed protein showed 71.28% of protein; ultrafiltration removed 70% of the total mineral content. Even so, the sample still showed 1.97% of sodium, demonstrating the need to carry out more diafiltrations. The hydrolysate has solubility higher than 88.5% in the pH 3 to 7, reaching 99.8% at pH 6. The sample had high foaming capacity, but low foam stability. Thus, enzymatic hydrolysis associated with ultrafiltration can be a suitable alternative for obtaining a soluble fraction with low sodium content, improving the quality of rice endosperm protein. (C) 2017 Elsevier B.V. All rights reserved.