Submitted to: American Association of Cereal Chemists Meetings
Publication Type: Abstract Only
Publication Acceptance Date: 6/25/2008
Publication Date: 7/25/2008
Citation: Ohm, J., Ostenson, A.M., Hareland, G.A., Doehlert, D.C., Senay, S. 2008. Extraction of starch from wheat flour by alkaline solution. American Association of Cereal Chemists Meetings. Cereal Foods World 53(4):71A
Technical Abstract: Separation of starch from wheat flour with high purity is very important for the analysis of starch such as amylose and amylopectin determination by size exclusion HPLC (SE-HPLC). A procedure that extracts starch from flour by ethanol precipitation after dissolving flour in KOH and urea solution was researched to improve extraction and analysis of wheat flour starch at micro scale, comparing with conventional dimethyl sulfoxide procedure. Isolated starches were characterized by SE-HPLC that separated starch molecules into high and low molecular weight amylopectin (AP) peaks and an amylose (AM) peak. Defatting of flour by refluxing in methanol helped to dissolve more starch from flour that was indicated by significantly larger peak areas of SE-HPLC. When compared with conventional dimethyl sulfoxide procedure, KOH and urea procedure extracted starch with higher purity that was evidenced by significantly lower protein, arabinose, xylose, and mannose contents and SE-HPLC of the starch extract showed the larger peak areas of amylopectin and amylose. Stability of starch was affected by pH adjustment during storage after dissolving in KOH and urea and SE-HPLC indicated that starch stored at pH 9 showed less degradation than pH 7. A significant negative correlation was shown between SE-HPLC peak areas of high molecular weight AP and AM among 14 wheat flours. Concurrently, AM peak and high molecular weight AP peak areas had significant correlations with flour peak viscosity measured by RVA, predominantly due to the variation among waxy and non-waxy wheats. The KOH and urea procedure offers advantage of extraction of starch with higher purity over a conventional procedure and could contribute to characterization of flour starches by analytical methods such as SE-HPLC and subsequent research on their associations with flour quality.