Structure and Orientation Changes of ö- and ç-Gliadins at the Air-Water Interface: A PM-IRRAS Spectroscopy and Brewster Angle Microscopy Study

Microscopic and molecular structures of ö- and ç-gliadin monolayers at the air-water interface were studied under compression by three complementary techniques: compression isotherms, polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). For high molecular areas, gliadin films are homogeneous, and a flat orientation of secondary structures relative to the interface is observed. With increasing compression, the nature and orientation of secondary structures changed to minimize the interfacial area. The ç-gliadin film is the most stable at the air-water interface; its interfacial volume is constant with increasing compression, contrary to ö-gliadin films whose molecules are forced out of the interface. ç-Gliadin stability at a high level of compression is interpreted by a stacking model