Structure of Wheat Gluten

For steric reasons, the cysteine residues C and C in the LMW subunits cannot form intramolecular disulfide bonds, but are available for intermolecular disulfide bridges, preferably with other LMW and HMW subunits (Fig. 15.10). 

HMW subunits of the x-type contain four and those of the y-type contain seven cysteine residues (Table 15.17). Except for the residue C in the y-type, all the residues are in the segments A and C (Fig. 15.12). In the x-type, the residues C and C form an intramolecular disulfide bridge (Fig. 15.12) and C and C are available for intermolecular bonding. The y-type contains five cysteine residues in segment A and one in each of the segments B and C (Fig. 15.12). Until now, intermolecular disulfide bonds to other 

HMW subsunits of the y-type as well as to LMW subunits could be detected (Fig. 15.12). 

It is noticeable that small amounts of a-, y- and m-gliadins are not extractable from flour with aqueous alcohol, but remain with the glutenins. It is assumed that these proteins contain an odd number of cysteine residues due to point mutations, one residue being available for intermolecu-lar disulfide bonding. In fact, it has been observed that LMW subunits are linked to y-gliadins which have 9 instead of 8 cysteine residues, via a bridge from to C (Fig. 15.10). 

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Blanch, E.W., Kasarda, D.D., Hecht, L., Nielsen, K., Barron, L.D. 2003. New insight into the solution structures of wheat gluten proteins from Raman optical activity. Biochemistry 42 5665-5673. 

Structure of Wheat Gluten in Relation to Functionality in Breadmaking... 

On the whole, the structure of wheat gluten has been so far evaluated to be able to describe variety-specific differences in the technological properties. 

VPGVP, which tends to form a type II P turn with proline in position 2 (Fig. 2-24) is present in long tandem repeats e.g., (VPGVG). These extensible regions alternate with short a helices which are crosslinked to other chains. Similar structures are present in silks (Box 2-B) and in proteins of wheat gluten. ... 

Shewry, PR., Halford, N.G., Field, J.M., and Tatham, A.S. The structure and functionality of wheat gluten proteins. Proceedings of the 38th Australian Cereal Chemistry Conference, Sydney, NSW, Murray, L. ed.. Royal Australian Chemical Institute, Melbourne, VIC, Australia, 1989. 

By varying reaction condititnis, the optimum extent of esterification was obtained for each kind of proteins. Table 1 shows the highest esterification values obtained from an experimental design. Sunflower proteins underwent esterification in a larger extent than wheat gluten proteins. Only 25 % of the carboxyl groups of wheat gluten could be esterified with this experimental procedure. The different structure of proteins may account for this difference. 

L-Glutamic acid from hyrolyzate of wheat gluten by H. Ritthausen. Structure W. Dittmer, 1872 W. Markovnikov, 1876. Synthesis from levulinic acid L. Wolff, 1890. 1877 L-Glutamine from sugar beet, E. Schulze, see glutamic acid. 

Wieser, H., Seilmeier, W, Belitz, H.-D. Use of RP-HPLC for a better understanding of the structure and the functionality of wheat gluten proteins. In High-Performance Liquid Chromatography of Cereal and Legume Proteins (Eds. Kruger, J.E., Bietz, J.A.), p. 235, American Assodation of Cereal Chemists St. Paul. Minn., 1994... 

Rye Proteins. While rye is the only European cereal able to completely replace wheat in bread, rye protein is not as effective as wheat protein. One reason for this is that as much as 80% of the protein in a rye sour dough is soluble compared with 10% of soluble protein in a wheat dough. One factor that inhibits the formation of a gluten-like complex is the 4-7% of pentosans present, which bind water and raise the viscosity of the dough. The crumb structure is then formed from the pentosans in combination with the starch. 

The ability of a degradable plastic to decay depends on the structure of its polymer chain. Biodegradable plastics are often manufactured from natural polymers, such as cornstarch and wheat gluten. Micro-organisms in the soil can break down these natural polymers. Ideally, a biodegradable plastic would break down completely into carbon dioxide, water, and biomass within six months, just like a natural material. 

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