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Water Solubility and Macromolecular Properties of Corn Meal Extrudates as Affected by Epichlorohydrin¹

¹Journal Series 11618, Agricultural Research Division, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. ²Visiting researcher, director, and postdoctoral research associate, respectively, Industrial Agricultural Products Center, University of Nebraska, Lincoln, NE 68583-0730. ³Presently with Food Research Institute, Aichi Prefectural Government, Japan. ⁴Corresponding author. E-mail: bsen024@unlvm.unl.edu. ⁵Presently research scientist, Banner Pharmacaps, Inc., 4125 Premier Drive, High Point, NC, and adjunct assistant professor, Department of Biological Systems Engineering, University of Nebraska, Lincoln, NE 68583-0726.

Degermed corn meal adjusted to 18% moisture content (db) with epichlorohydrin (ECH) content at 0, 0.5, 1, or 2% (w/w) were extruded with a twin-screw laboratory extruder at a screw speed of 140 rpm. Compression and metering barrel zones were set at 100, 120, or 140°C. Water solubility (WS) of ground extrudates ranged from 7.6 ± 1.1% to 14.3 ± 1.3%. ECH content had a significant (P < 0.01) negative effect on WS, while barrel temperature and the interaction between barrel temperature and ECH content were not significant (P > 0.05). Presumably, ECH reduced WS of extrudates through cross-linking between hydroxyl groups on starch and protein molecules. Gel-permeation chromatography patterns for both 100 and 140°C barrel temperatures showed that high molecular weight carbohydrates in the extrudates decreased with increasing ECH content without a simultaneous increase in low molecular weight carbohydrates. This suggested that the decrease in high molecular weight fractions was due to insolubilization by cross-linking rather than degradation. SDS-PAGE revealed that two protein bands of ≈29 and 17.5 kDa disappeared, and a new band appeared at 45 kDa with increasing ECH content. This indicated that, most likely, ECH reacted with protein in addition to reacting with starch. However, glycoprotein and starch-protein complexes were not identified with electrophoresis.