Relating the protein composition and air-water interfacial properties of aqueous flour extracts from wheats grown at different nitrogen fertilization levels

Aqueous phase extractable proteins from wheat can play a functional role in foods requiring interfacial stabilization. We here investigated the (protein) composition of aqueous flour extracts from wheats grown at different nitrogen (N) fertilization levels and studied their air-water interfacial characteristics. An important finding was that alpha- and gamma-gliadins were extracted from wheat flour with water, even to an extent that they in the present work comprised 62-71% of the extract proteins. Application of N fertilization during wheat cultivation led to flour extracts with higher foam stabilities and air-water interface dilatational moduli. In all cases, proteins were found to most likely be the dominant constituent at the air-water interface. Analysis of foam protein compositions revealed an enrichment of proteins with molecular weights matching those of alpha- and gamma-gliadins. It thus seems that gliadins can to a large extent determine the foaming characteristics of aqueous wheat flour extracts.