Cereal proteins denaturation

Saio, K. K. Kobayakawa M. Kito. Protein denaturation during model storage smdies of soybeans and meals. Cereal Chem. 1982, 59, 408-412. 

Electrophoretic techniques are also highly popular in protein food analysis. Polyacrylamide gel-based separation, either depending on the protein size in denaturing conditions or on its charge in specific solvent systems (as exemplified by those used for analysis of cereal proteins), is still highly popular because of their good sensitivity, ease of use, and capability to compare a relatively large number of samples on the same gel. This unique combination of features makes electrophoresis a popular choice also from an economic standpoint. 

It is not possible to extrude all types of protein, and considerable protein denaturation may occur when some proteins are extruded. Lawrie and Ledward (1988) found in their review that proteins extracted from offal could not be extruded successfully but that mixtures of offal proteins and cereals such as soya grits could be co-extruded. 

From the nutritional point of view, denaturation is usually desirable since denatured proteins are more amenable to digestive enzymes than the native proteins. Denaturation, therefore, increases the bioavailabihty of proteins (e.g. sulfur-containing amino acids in cereals and legumes). Some antinutritional and natural toxic substances are also denatured, such as protease inhibitors (see Section 10.2.1.1), lectins (see Section 10.2.2.6), enzymes and other unwanted proteins and undesirable microorganisms. 

Nowadays, most breakfast cereals are made either by original traditional processes or by using alternative extrusion methods. Commercial flakes, shreds, and oven-puffed cereals could be alternatively manufactured via extrusion. There are two major types of extrusion processes cold and thermoplastic. Cold extrusion is almost exclusively applied for production of pasta products (Chapter 10), whereas thermoplastic extrusion is used for manufacturing breakfast cereals and snack foods (Chapter 12). Undoubtedly, the most popular and versatile extrusion process is thermoplastic, defined as the combination of heat and mechanical shear to enhance starch gelatinization and dextrinization, protein denaturation, and inactivation of microorganisms, enzymes, and antinutritional factors. The changes in the properties of the starch and proteins result in the formation of a plastic material that could be formed and/or restructured into desired configurations. 

In food processing, the major objectives are sometimes achieved at the expense of some loss of recognised nutrients. However, in other cases, important nutrients may become available only after appropriate processing, since inhibitors or other interfering compounds may be destroyed or inactivated. Toxic factors can sometimes be destroyed by denaturation, as with enzymes, protease inhibitors and phyto-haemagglutinins. They can also be physically removed, for example by leaching, solvent extraction or solid classification methods, as in the removal of gossypol from cottonseed protein, or of phytate from cereals. 

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