Authors: Suchy J.¹; Lukow O.M.¹; Fu B.X.²

Source: Journal of the Science of Food and Agriculture, Volume 83, Number 10, August 2003 , pp. 1083-1090(8)

Publisher: John Wiley & Sons, Ltd.

Abstract:

Wheat protein composition is important for understanding the biochemical basis of wheat quality. The objective of this study was to design a simple protein fractionation protocol with low cross-contamination and to show that these protein fractions were associated with wheat quality. The protocol consists of three sequential extractions from 100 mg of flour with 7.5% propan-1-ol and 0.3 M sodium iodide (monomeric-rich protein), 50% propan-1-ol (soluble glutenin-rich protein) and 40% propan-1-ol and 0.2% dithiothreitol (insoluble glutenin-rich protein). Nitrogen content of protein solubility groups was determined from dry residues using an automated combustion nitrogen analyser. About 90% of the total protein in the flour was solubilised. Cross-contamination of protein fractions was evaluated by SDS-PAGE, SE-HPLC and RP-HPLC. Variation in nitrogen content of the protein solubility fractions was lowest for monomeric-rich protein (<2%) and insoluble glutenin-rich protein (<4%). Three wheats with similar high-molecular-weight (HMW) glutenin subunit composition, Alpha 16, Glenlea and Roblin, varied significantly (P 0.05) in the proportion of monomeric-rich and insoluble glutenin-rich protein in the flour. Dough rheological properties were directly related to the proportion of insoluble glutenin-rich protein and inversely related to the proportion of monomeric-rich protein. The protocol was validated using an expanded set of 11 wheats which also showed that inter-cultivar differences in the proportion of monomeric-rich, insoluble glutenin-rich protein and glutenin-to-gliadin ratio in the flour governed dough rheological properties such as mixograph, farinograph and microextension tests. The protocol has merit for quality screening in wheat-breeding programmes when the sample size is too small or when time constraints limit the ability to perform traditional rheological tests. For the Department of Agriculture and Agri-Food, Government of Canada, Copyright © Minister of Public Works and Government Services Canada 2003. Published for SCI by John Wiley & Sons, Ltd.

Keywords: wheat protein fractionation; monomeric protein; soluble glutenin; insoluble glutenin; residue protein; HMW-GS; LMW-GS; glutenin-to-gliadin ratio; Dumas combustion; nitrogen; wheat quality; mixograph; farinograph; microextension

Document Type: Research article

DOI: http://dx.doi.org/10.1002/jsfa.1438

Affiliations: 1: Agriculture and Agri-Food Canada, Cereal Research Centre, 195 Dafoe Road, Winnipeg, MB, R3T 2M9, Canada 2: Canadian International Grains Institute, 1000-303 Main Street, Winnipeg, MB, R3C 3G7, Canada

Publication date: 2003-08-01

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