Interaction of puroindolines with wheat flour polar lipids determines their foaming properties

The interaction of puroindolines with wheat polar lipids and the stability of the corresponding puroindoline foams were investigated. Whereas puroindoline-a is capable of binding tightly to both wheat phospholipids and glycolipids, puroindoline-b interacts tightly only with negatively charged phospholipids and forms loose lipoprotein complexes with glycolipids. Both ionic, hydrogen, and hydrophobic bonds contribute to the stability of puroindoline-polar lipid complexes, and the integrity of tryptophan-rich domain is essential for the interaction with neutral polar lipids. Compared with egg white proteins, chosen as a model of nonlipid binding and good foaming food proteins, puroindolines exhibit excellent foam stability, especially in the presence of wheat polar lipids. The higher efficiency of puroindoline-a than puroindoline-b to prevent foam destabilization by wheat polar lipids highlights the close relationships between lipid binding and foaming properties of these wheat proteins. These results indicate that puroindolines would be good candidates to play a major role in the formation and stability of bread dough foams.