Isolation of gluten from wheat flour and its structural analysis

Gluten is commonly known as cereal grain-associated protein. In wheat, it accounts for 85% of endosperm protein and contains high levels of amino acid units, i.e., proline, glycine, and glutamine. It contains low levels of amino acids that have ionizable side chains, among which gluten plays a primary role. Gluten provides unique viscoelasticity to wheat dough, allowing the production of different wheat-generated foods like bread, barley, porridge, crackers, biscuits, muesli, pancakes, pasta, and noodles. Gluten is very sensitive to heat in moist form, and even low temperature destroys its viscoelastic and cohesive properties, which make it unique among food proteins. This chapter will discuss the importance, structural features, occurrence, and different methods of isolation of gluten from wheat and their effectiveness. Generally, Gluten is isolated from wheat by soaking the wheat grains and then washing them to remove starch or by kneading the wheat flour with water and removing starch in a running water stream. The insoluble part of wheat constitutes raw gluten. Gluten is very sensitive to temperature; thus, it is difficult to obtain in dry form. Freeze-drying is the only method that efficiently reduces impacts on the gluten characteristics in the drying process. The second part of the chapter will focus on the structural properties and structural analysis of gluten. The gluten structural characteristics are mainly determined by Raman microscopy, scanning electron microscopy, Fourier Transform Infrared spectroscopy, mass spectroscopy proton, and 13C nuclear magnetic resonance techniques. Reverse-phase high-performance liquid chromatography (HPLC) is also used for the study of the nonlinear properties of gluten. Moreover, hyphenate techniques such as HPLC/MS, and LC/MS are used for the structural analysis of gluten. Overall the chapter will provide useful information regarding the isolation of gluten from wheat flour and its structural analysis.