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Walter Bushuk Graduate Research Award - Development of improved methods to evaluate the gluten quality of wheat flours
S. M. THANHÄUSER (1), H. Wieser (1), P. Köhler (1). (1) German Research Center for Food Chemistry, Freising, Germany

The ultimate method to assess the baking quality of wheat flour is the baking test since all stages of breadmaking including storage are considered. However, as baking tests are time-consuming and difficult to perform, quick and easy-to-use methods are being carried out and the obtained parameters are correlated with the baking quality. The objective of this study was to establish protein parameters for wheat flour quality evaluation, such as the concentrations of gliadins (GLI), glutenins (GLU), and glutenin macropolymer (GMP). The focus should be laid on the development of simple assays for protein quantitation based on colorimetry and fluorimetry. In a set of wheat cultivars approved in Germany including all baking quality classes GLI, GLU and GMP fractions were quantitated by means of different extraction/HPLC methods, as well as by colorimetric and fluorimetric methods such as the Bradford, the bicinchoninic acid, the fluorescamine and the naphthol blue black (NBB) assay. To get reliable results the assays had to be calibrated with the protein fractions that were quantitated. Thus, reference materials were prepared in a semi-preparative scale prior to the analyses. The GLIA (r=0.80), GLUT (r=0.76) and GMP (r=0.8) contents were highly correlated with the baking quality determined by means of a baking test with mixing of dough to peak consistency (micro-baking-test; MBT) but not with a baking test using a fixed mixing time at high speed (micro-rapid-mix test; MRMT). Hence, GLIA, GLUT and GMP contents are suitable parameters to assess the baking quality of wheat flour. Among the colorimetric assays, the NBB test had the best reproducibility. Furthermore, this assay had the potential to be established as a simple high throughput method for determining technologically relevant protein parameters of wheat flour.

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