The　physicochemical,　structural　and　functional　properties　of　citric-acid-deamidated　wheat　gluten　at　controlled　degrees　of　deamidation　(25%,　40%　and　55%),　which　were　obtained　by　using　different　acid　concentrations　(3.93　x　10(-5),　3.14　x　10(-3)　and　2.36　x　10(-2)　mol/L)　and　temperatures　(70　degrees　C　2　h,　90　degrees　C　1h　and　110　degrees　C　40　min),　were　compared.　Various　deamidation　processing　conditions　leading　to　the　same　degree　of　deamidation　resulted　in　proteins　with　different　physicochemical　and　structural　characteristics,　as　indicted　by　the　degree　of　hydrolysis,　Z-potential,　surface　hydrophobicity,　particle　size,　SDS-PAGE　results,　SEC-HPLC　results,　intrinsic　fluorescence　and　FTIR　spectra.　Agglomerative　hierarchical　clustering　analysis　and　principal　component　analysis　qualitatively　indicated　a　significant　effect　of　pH　on　protein　deamidation.　Three　samples　at　40%　deamidation,　which　were　produced　by　a　moderate　acid　concentration,　showed　the　best　emulsifying　and　foaming　properties.　Processes　conducted　at　greater　than　90　degrees　C　causing　protein　aggregation　and　at　a　high　acid　concentration　rupturing　peptide　bonds,　impaired　protein　quality.　These　findings　demonstrated　that　a　limited　amount　of　H+　could　function　well　in　the　catalysis　of　the　deamidation　of　amide　groups　without　an　excess　of　H+,　which　hydrolyses　peptide　bonds　in　a　stronger　hydrothermal　treatment.　(C)　2016　Elsevier　Ltd.　All　rights　reserved.