COMPETITIVE ADSORPTION BEHAVIOR OF WHEAT-FLOUR COMPONENTS AND EMULSIFIERS AT AN AIR-WATER-INTERFACE

This study aimed to characterise the competitive adsorption behaviour of the different components present in wheat flour and emulsifiers use d in breadmaking at an air-water interface using surface balance measu rements. It was found that the proteins could be arranged in increasin g order of surface activity: albumin < globulin < glutenin < gliadin. Furthermore, the ability of the proteins to interact with and/or to in sert into lipid monolayers was found to correlate with their surface a ctivities. The ability of gliadin to insert into emulsifier monolayers was comparable to its ability to insert into lipid monolayers. Compet ition experiments with pure protein monolayers, and the subsequent add ition of different lipid or emulsifier suspensions, revealed that non- bilayer forming lipids were more effective at adsorbing to and competi ng at the air-water interface than bilayer forming lipids. It was foun d that proteins could not insert into lipid or emulsifier monolayers a bove a surface pressure of 37 mN/m, whereas a wheat lipid mixture coul d reach a surface pressure of approximately 50 mN/m. If sufficient amo unts of lipids are available to reach the gas cell interface in dough, it is likely that lipids will expel the proteins from the interface a nd that lipids and/or emulsifiers will be the only constituents left i n the gas cell film. This study indicates that future studies addressi ng the issue of gas-cell stability in a wheat flour dough should focus on the behaviour of lipid and emulsifier monolayers. (C) 1997 Academi c Press Limited.