2001 AACC Annual Meeting Charlotte, North Carolina October 14-18, 2001 Charlotte Convention Center

Wheat bran water-unextractable cell wall material (WUS) was obtained with a yield of ca 45% by enzymatically (Termamyl 120L and Neutrase 0.8L) removing starch and proteins from industrial wheat bran. The water-extractable AX in wheat bran amounted to 6% of the total AX content and were present as lowly substituted polysaccharides. Two consecutive extractions of WUS with alkaline hydrogen peroxide (AHP; 2.0%, pH 11.5, 60 C, 4 h) resulted in a 61% loss of material. The remaining residue (CRR) was rich in cellulose and contained 33% of the AX originally present in WUS. Because of the selective extraction of highly substituted AX by dilute alkali, the arabinose to xylose (A/X-) ratio of AX in CRR was lower than that in WUS. During two consecutive extractions of WUS with AHP, ca. 45% of the AX originally present in WUS was extracted. The alkali-extractable AX were present as polymers with a high A/X-ratio (0.82) and their elution profiles shows two polydisperse peaks with an apparent molecular weight of respectively 100-120 kDa and 6-10 kDa. When the alkaline extracts were fractionated by means of graded ethanol precipitation, two different AX populations were distinguished. A lowly substituted fraction (A/X = 0.40) was recovered at 20% and between 20 and 40% ethanol. A second major fraction with highly substituted AX was obtained at ethanol concentrations between 40 and 60% and between 60 and 70%. Those fractions comprised respectively 23% and 18% of the AX originally present in WUS and the present AX had a A/X-ratio of respectively 0.95 and 1.12.