Competitive adsorption behaviour 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 used in breadmaking at an air-water interface using surface balance measurements. It was found that the proteins could be arranged in increasing order of surface activity: albumin < globulin < glutenin < gliadin. Furthermore, the ability of the proteins to interact with and/or to insert into lipid monolayers was found to correlate with their surface activities. The ability of gliadin to insert into emulsifier monolayers was comparable to its ability to insert into lipid monolayers. Competition experiments with pure protein monolayers, and the subsequent addition of different lipid or emulsifier suspensions, revealed that non-bilayer forming lipids were more effective at adsorbing to and competing at the air-water interface than bilayer forming lipids. It was found that proteins could not insert into lipid or emulsifier monolayers above a surface pressure of 37 mN/m, whereas a wheat lipid mixture could reach a surface pressure of approximately 50 mN/m. If sufficient amounts of lipids are available to reach the gas cell interface in dough, it is likely that lipids will expel the proteins from the interface and that lipids and/or emulsifiers will be the only constituents left in the gas cell film. This study indicates that future studies addressing the issue of gas-cell stability in a wheat flour dough should focus on the behaviour of lipid and emulsifier monolayers. (C) 1997 Academic Press Limited.