Moderate heat enhances gliadin-proanthocyanidin interactions

Understanding wheat gliadin-proanthocyanidin (PA) interactions would be useful to systematically control foams and gels, create novel textures, and reduce inflammatory reactions. This work aimed to determine the effects of heat (50-90 °C) on gliadin-proanthocyanidin (PA) interactions. Gliadin-PA mixtures were heated for 30 min in aqueous ethanol, and resulting morphology, fluorescence, and MW distribution were analyzed. Atomic force microscopy showed that PA greatly increased gliadin particle size, especially with heat. PA significantly quenched gliadin's tryptophan fluorescence. Further fluorescence data analysis indicated that PA interacted with gliadins through static quenching, primarily via hydrophobic interactions, and that 75 °C treatment yielded the greatest gliadin-PA interactions, likely because the proteins unraveled and exposed residues for interaction. PA appeared to interact mostly with ω-gliadins, based on their absence in the SDS-PAGE gel. Though it has been overshadowed in previous studies by non-covalent interactions, staining of quinoproteins indicated that PA covalently cross-linked gliadins at pH ∼ 6.