Modification of Mung Bean Protein Isolate Structure and Functionality by Freeze-Thaw Process

This study investigated changes of the structural and functional properties of mung bean protein isolate (MPI) during multiple freeze-thaw cycles. Results showed that freeze-thaw treatment did not affect protein electrophoresis patterns but induced a more disordered secondary protein structure of MPI. The exposed sulfhydryl content and surface hydrophobicity of MPI increased first and then decreased, while, protein denaturation enthalpy decreased first and then increased, indicating the unfolding and rearrangement of protein conformation during multiple freeze-thaw cycles. The particle size diameter of MPI trended to increase as a result of freeze-thaw treatment. The foaming capacity, foaming stability, emulsifying activity index, and emulsifying stability index of MPI significantly improved by the freeze-thaw process. MPI treated with 1 freeze-thaw cycle had comparable foaming properties to soy protein isolate. However, freeze-thawing up to 5 cycles led to a negative effect on protein functionality, especially the foaming stability. Results suggested that the freeze-thaw process modified protein structure resulting in the improvement of the functional properties of MPI.