Читать книгу Biomolecules from Natural Sources - Группа авторов - Страница 61

Wheat gluten is a protein by-product of the starch fabrication. In addition to wheat, grain sources of gluten are barley, rye, triticale, spelt, einkorn, emmer and kumut. It is available in high quantity and at low cost [137]. Gluten is a part of our food and is contained in pasta, bread, cereals, soups, deserts, soy sauce, hydrolyzed wheat proteins, wheat bran hydro lysate, wheat protein isolate, wheat starch, glucose syrups, wheat maltodextrin, sorbitol, lactitol, maltitol, caramel, glucan, alcohol/ ethanol, vinegar, wheat germ oil, medications, and so on. They are relatively impermeable to oxygen and to CO₂ but are sensitive to humidity. Potential applications are producing soluble receptacles for the controlled release of a chemical product (such as toilet detergent). Wheat gluten contains two main groups of proteins, gliadin and glutenin [138]. Gliadins are protein molecules with disulphide bonds. They have low molecular weight and a low level of amino acids with charged side groups. Gliadin has antimicrobial activity and is used in food packaging and coating applications [130, 139].

The molecular weight of glutenins is at least ten times higher than that of gliadins. Wheat gluten materials have the fastest degradation rates. Gluten is fully biodegradable and the products obtained are non-toxic. Wheat gluten has proved to be an excellent film-forming agent [18, 140]. In practice, the term “gluten” refers to the proteins, because they play a key role in determining the unique baking quality of wheat by conferring water absorption capacity, cohesivity, viscosity and elasticity to dough. It is also used for improving solubility, emulsification, and film-forming properties [22, 141, 142]. The amino acid compositions of glutenins are similar to those of gliadins, with high levels of glutamine and proline and low levels of charged amino acids. Glutenins can be broadly classified into two groups, the high molecular weight (HMW) and the low molecular weight (LMW) subunits.