Protein wheat, hydration

Solid state 13C CPMAS NMR spectra of Wheat High Molecular Weight (W.HMW) subunits show well resolved resonances identical with spectra of dry protein and peptide samples [24], Most of the amino acids side-chain resonances are found in the 0-35 ppm region followed by the alpha resonances of the most abundant amino acids glycine, glutamine and proline at chemical shifts of 42, 52 and 60 ppm, respectively, and the carbonyl carbons show a broad peak in 172-177 ppm region. The CPMAS spectra of hydrated whole HMW provides important information on the structural characteristics. 

Starch changes during cooking of pasta are reported to vary from a hydration-driven gelatinization process in the outer layer to a heat-induced crystallite melting in the center.525 It is speculated that both the state of the starch and the surface structure contribute to the development of the elastic texture and stickiness of pasta. Interactions between starch and the surrounding protein matrix are evident in the outer and intermediate layer. In the center of cooked pasta, wheat starch granules retain their shape due to limited water diffusion, and the protein network remains dense. 

A commercial fractionation process in which groats are dry-milled and the comminuted groats are soaked in a solution of cellulases and hemicellulases has been developed.9 In addition to the starch the process produces fiber and protein fractions. Unlike wheat starch, oat starch cannot be separated from the grain by selective hydration and centrifugation, because of hydrated bran and protein layers. 

Wheat Gluten occurs as a cream to light tan, free-flowing powder. It is the water-insoluble complex protein obtained by water extraction of wheat or wheat flour. It is soluble in alkalies, and partly soluble in alcohol and dilute acids. Vital Wheat Gluten is characterized by high viscoelasticity when hydrated, while Devitalized Wheat Gluten has lost this character because of denaturation by heat. 

Proteins are natural, renewable, and biodegradable polymers which have attracted considerable attention in recent years in terms of advances in genetic engineering, eco-friendly materials, and novel composite materials based on renewable sources. This chapter reviews the protein structures, their physicochemical properties, their modification and their application, with particular emphasis on soy protein, zein, wheat protein, and casein. Firstly, it presents an overview of the structure, classification, hydration-dehydration, solubility, denaturation, and new concepts on proteins. Secondly, it concentrates on the physical and chemical properties of the four important kinds of proteins. Thirdly, the potential applications of proteins, including films and sheets, adhesives, plastics, blends, and composites, etc. are discussed. 

The hydration of proteins from wheat seeds has been studied using solid-state CPMAS and... 

The activity of a soluble DNA polymerase in wheat embryos starts to increase during the first six hours after imbibition commences and continues to do so for at least the 1st day [91]. DNA replication occurs after radicle expansion, some 15 h after the initial hydration of the embryo [90]. The polymerase appears to be synthesized de novo during germination, for if protein synthesis is inhibited during the first nine hours then subsequent DNA synthesis is inhibited. Inhibition of protein synthesis at times after nine hours is progressively less effective in preventing DNA synthesis, presumably indicating that critical levels of the polymerase are synthesized prior to the ninth hour. 

In order to optimise the process parameters (temperature, plasticiser content, residence time and so on), during the transformation of material proteins, the specific characteristics of each protein should be determined (thermal, mechanical and chemical sensitivities, and high viscosities of the rubbery phases above the Tg) for these new raw materials. However, the physico-chemical factors involved in these processes are unclear because very little is currently known about protein modifications that take place when processing at high temperature under low hydration conditions [182]. This has mainly been determined for wheat gluten-based materials [71,74,75]. 

Wheat is very suitable for bread making because the dough produced has elastic properties. This is due to the gluten (hydrated insoluble protein) present. The amount and quality of the gluten is a varietal characteristic, but it can also be affected by soil fertility and climatic conditions. 

Wheat protein fractionation by the Osborne method provides prolamins and glutelins in a ratio of 1 1. Both fractions, in hydrated form, have different effects on the rheological characteristics of dough prolamins are responsible, preferentially, for viscosity, and glutelins for dough strength and elasticity. 

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