Effects of Deletions of High Molecular Weight Glutenin Subunit Alleles on Dough Properties and Wheat Flour Tortilla Quality
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In wheat (Triticum aestivum L), high molecular weight glutenin subunits (HMW -GS) are synthesized by the loci Glu-A1, Glu-B1, and Glu-D1 on the long arm of group 1 chromosome, and their variants play a significant role in the functional properties of flour; hence dough properties and tortilla quality. This study was conducted to understand the effects of HMW-GS on dough properties and tortilla quality using 40 different wheat lines from two different locations; Texas Agrilife Experiment Station at McGregor, and at Castroville, Texas, in 2010. Wheat lines in which one or more of these loci were absent (deletion lines) and non-deletion lines were used. Flours were evaluated for insoluble polymeric protein (IPP) content and mixograph properties. Dough properties; compression force, stress relaxation test, and dough extensibility, were determined using a texture analyzer. Tortillas were produced by hot-pressed method and evaluated for physical properties and textural change during 16 days of storage. Flour from deletion lines had lower average IPP content (38.4%) than non-deletion lines (41.9%). Dough from deletion lines were more extensible (44.8 mm) and required lower equilibrium force from stress relaxation test (4.91 N) compared to non-deletion lines (34.2 mm, and 6.56 N, respectively). Deletion lines produced larger diameter tortillas (177 mm) than non-deletion lines (165 mm) and had lighter color (L* = 82.3) than tortillas from non-deletion lines (L* = 81.0). Most of the deletion lines interestingly produced tortillas with acceptable flexibility scores on day 16 of storage (>= 3.0). Flour IPP content (r = -0.57) and equilibrium force (r = -0.80) were negatively correlated with tortilla diameter, but positively correlated with 16 day flexibility scores (r = 0.72, and r = 0.68, respectively). In general, deletion at Glu-A1 or Glu-D1 or presence of 2+12 instead of 5+10 allelic pair at Glu-D1 locus produced large diameter tortillas, but with poor day 16 flexibility. However, combination of 7+9 at Glu-B1 locus with deletions at Glu-A1 or Glu-D1 or 2+12 at Glu-D1 consistently produced tortillas that had large diameter and retained good flexibility scores during 16 days of storage. The results indicate the presence of 7+9 at Glu-B1 may play a crucial role in selection of wheat varieties for tortilla making.
Tuncil, Yunus (2012). Effects of Deletions of High Molecular Weight Glutenin Subunit Alleles on Dough Properties and Wheat Flour Tortilla Quality. Master's thesis, Texas A&M University. Available electronically from