Influence of glutaminase-assisted extraction at varied pH on the physicochemical properties and functionalities of pea proteins

Protein glutaminase (PG)-assisted extraction has been demonstrated to increase plant protein recovery yield and protein solubility. However, the combined influence of extraction pH and PG inclusion during extraction on the structure, functionality and in-vitro digestibility of extracted plant proteins remains largely unknown. This study compared PG-500-assisted extraction of pea proteins (D-PP) with traditional alkaline extraction (PP) at pH 7, 8, and 9. D-PP showed similar to 26 %, 6 %, and 5 % increment on protein recovery yield extracted at pH 7, pH 8, and pH 9, respectively. D-PP extracted at pH 7 and pH 8 showed higher negative surface charge under neutral to alkaline conditions compared to PP, while no significant difference was observed when extracted at pH 9. Surface hydrophobicity and sulfhydryl group content of D-PP were consistently lower than those of PP, regardless of extraction pH. SDS-PAGE showed similar protein bands between D-PP and PP samples, indicating PG-500 did not induce proteolysis. Differential scanning calorimetry (DSC) showed D-PP extracted at pH 7 had higher onset (T-O) and denaturation temperature (T-P), but lower enthalpy (Delta H) compared to PP, with no difference observed at pH 8 and pH 9. Gelation dynamics showed a comparable or higher storage modulus (G') for D-PP extracted at pH 7 and pH 8, but a reduced G' extracted at pH 9 compared to PP. Emulsification and foaming capacity were improved only for D-PP extracted at pH 7, water-holding and oil-binding capacity decreased. In-vitro digestion showed no significant differences in apparent protein digestibility between D-PP and PP across all extraction pHs.