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Food Structure

Abstract

This paper reports on a combined electron microscopy and X-ray diffraction study of gluten gel, in which conventional gluten, a delipidized gluten sample and a storage protein fraction obtained by salt-fractionation were used. It can be concluded that the gluten gel is a continuous phase of densely packed protein units. Other structural components such as air ce lls, lipid droplets, liposomes, fiber residues, starch granules etc. are dispersed in the continuous matrix. The space available for water is strictly limited in the continuous phase due to the dense packing of protein molecules. Water that is not completely separated from the gel during preparation is therefore expelled at interfaces between the continuous phase and other structural components and water-rich domains are thus formed. The dense protein matrix is very stable and not significantly influenced by the methods used for gluten preparation, gel formation or preparation for electron micr~scopy. The microstructure of. the prot'bin matrix remamed the same, even after heat1ng a t 95 C. There is a close analogy between the gluten gel and the L2 phase in aqueous systems of simple amphiphiles, and it is proposed that the structure consists of globular aggregates with hydrophobic cores and a hydrophilic surface zone forming a continuum. The results clearly show that the formation of the gluten gel is due to proteins only, nat to lipid-protein interaction, as was often proposed in previous studies.

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