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United States Department of Agriculture

Agricultural Research Service

Title: Methods for Analyzing Polymeric Proteins of Wheat and Their Impact on Wheat Quality

Authors
item Lookhart, George
item Bean, Scott

Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: March 17, 2003
Publication Date: March 17, 2003
Citation: Lookhart, G.L., Bean, S. 2003. Methods for analyzing polymeric proteins of wheat and their impact on wheat quality. American Association of Cereal Chemists Pacific Rim Meeting. Abstract Book p. 17.

Interpretive Summary: Presentation at the AACC Pacific Rim Meeting held March 17-19, 2003, in Honolulu, Hawaii.

Technical Abstract: The polymeric proteins of wheat have been found correlated to wheat quality attributes such as mixing strength. Because of this improved methods for characterizing these proteins were developed and applied to the study of wheat quality. A rapid method for measuring the amount of insoluble polymeric protein was developed based on short, multiple extractions with 50% 1-propanol followed by nitrogen combustion analysis. Good correlations between dough strength parameters and amounts of pellet protein and % pellet protein (pellet protein/flour protein) were found for all samples. This procedure was found to be simple and rapid, with the potential of analyzing over 100 samples per day with good reproducibility. In addition, a method was developed to measure the actual size distribution of the polymeric proteins. This method used multi-angle laser light scattering (MALLS) in conjunction with size exclusion chromatography (SEC). Four solvent systems for analyzing wheat gluten proteins by MALLS were evaluated for use in extraction and as SEC mobile phases. The dn/dc values for wheat proteins were measured in each solvent. While all solvents showed similar resolution when used as mobile phases in SEC analysis, the SDS solvent extracted the most protein (~82%) in the unreduced form. This solvent system also displayed no concentration dependent or electrostatic effects during MALLS analysis. The SDS soluble and insoluble protein complexes were characterized by MALLS and Mw distributions ranging up to 8.1 x 106 Da were found for the insoluble SDS-protein complexes. The effect of the column void volume was also examined as was data analysis parameters such as fitting method, peak placement, etc... This method could be used to measure the size distribution of polymeric proteins in wheats differing in quality.

Last Modified: 12/21/2014