Foaming properties of tryptic gliadin hydrolysate peptide fractions

A tryptic gliadin hydrolysate was separated into central domain (CD) or terminal domain (TD) related peptide fractions. Whereas the initial foam volume (FV) of CD peptide fractions remained constant as a function of pH, FV of TD peptide fractions increased from acidic to alkaline pH. Foam stability (FS) of CD peptide fractions was maximal near neutral pH. For TD peptide fractions, one fraction showed maximal FS at strongly alkaline pH, while the other showed no clear maximal FS. CD related peptide foams contained higher levels of hydrophobic peptides than the respective solutions, while small differences were observed for TD peptide fractions. Peptide compositions of foams did not vary with pH, indicating that the foaming properties of gliadin peptides are mainly dictated by charges. As the pH dependent foaming properties of TD related peptides resemble best those of gliadin, it was concluded that the pH dependent foaming properties of gliadins are mainly determined by their TDs.