A A C C   2 0 0 0   A n n u a l   M e e t i n g

Since the rheological properties of wheat flour dough are determined mainly by "gluten strength," one of the most important objectives of a wheat breeding program is to optimize the strength of the gluten. Genetic and biochemical experiments have shown that flour end use quality is associated with the relative distribution of monomeric proteins (MP) (eg. gliadins) and high and low molecular glutenin subunits (HMWG-S and LMWG-S respectively) and their polymers. I have found that the gluten of "strong gluten" type varieties with higher ratios of HMWG and LMWG has higher densities and probably lower "packing defects" and contains less buried water. The intra-molecular "packing defects" must be genetically determined through controlled "chain-length" recognition. When unmatched chains, or aggregates with different surface charges and shapes come together, cavities or inter-domain "packing defects" will occur. In the "weak gluten" types the cavities between the domains (inter-molecular) in the gluten mass must be created by the large amount of monomeric and LMWG subunits and/or LMWG polymers. They are likely sandwiched between the HMWG and LMWG polymers and trapped with or without weak electrostatic interactions. At certain "points" hydrophobic side chains are in contact and can enhance weaker associations. Therefore, with higher MP and LMWG content, the overall attractive forces within the gluten mass are weaker and considering the increased ratio of total free accessible surface area of the native protein to the total free accessible surface area of the unfolded (trans) protein, the thermostability of the gluten also increases. I believe that the intrinsic differences between the HMW subunits are much less important than the ratio of HMWG to LMWG polymers and MP and their arrangements into their genetically predefined "SHAPE."