WATER SOLUBILITY AND MACROMOLECULAR PROPERTIES OF CORN MEAL EXTRUDATES AS AFFECTED BY EPICHLOROHYDRIN

Degermed corn meal adjusted to 18% moisture content (db) with epichlor ohydrin (ECH) content at 0, 0.5, 1, or 2% (w/w) were extruded with a t win-screw laboratory extruder at a screw speed of 140 rpm. Compression and metering barrel zones were set at 100, 120, or 140 degrees C. Wat er 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 tem perature and ECH content were not significant (P > 0.05). Presumably, ECH reduced WS of extrudates through cross-linking between hydroxyl gr oups on starch and protein molecules. Gel-permeation chromatography pa tterns for both 100 and 140 degrees C barrel temperatures showed that high molecular weight carbohydrates in the extrudates decreased with i ncreasing ECH content without a simultaneous increase in low molecular weight carbohydrates. This suggested that the decrease in high molecu lar weight fractions was due to insolubilization by cross-linking rath er than degradation. SDS-PAGE revealed that two protein bands of appro ximate to 29 and 17.5 kDa disappeared, and a new band appeared at 45 k Da with increasing ECH content. This indicated that, most likely, ECH reacted with protein in addition to reacting with starch. However, gly coprotein and starch-protein complexes were not identified with electr ophoresis.