Barium hydroxide as a tool to extract pure arabinoxylans from water-insoluble cell wall material of wheat flour
1991
Gruppen, H. | Hamer, R.J. | Voragen, A.G.J.
Water-insoluble cell wall material (WIS) prepared from wheat flour was extracted with various solvents. The extracts were compared in terms of yield, sugar composition, amino acid composition and molecular weight distribution. With 1 M NaOH, 1 M hydroxylamine hydrochloride, saturated Ba(OH)2 and 4-methylmorpholino-N-oxide (MMNO) most of the WIS was extracted, whereas 0.05 M Na2CO3, 8 M urea and dimethylsulphoxide (DMSO) only extracted a small part. Fractions enriched in glucan content could be extracted using MMNO and DMSO. Pure arabinoxylans were extracted in limited amounts with Na2CO3. Ba(OH)2, extraction, however, yielded a pure arabinoxylan fraction which represented c. 80% of all the arabinoxylan present in the WIS and a second fraction containing arabinoxylans and glucans. The various extracts showed almost no differences in protein contents and amino acid compositions. Most extracts had similar molecular weight distribution patterns. Light scattering analyses showed the molecular weight of these fractions to be c. 850000. Application of Ba(OH)2 extraction to wheat flour WIS from other wheat varieties, wheat bran, oat spelt xylan and starch-containing wheat flour WIS also resulted in selective extraction of arabinoxylans. The presence of NaBH4 in the saturated Ba(OH)2 solution appeared to be important for the selective extraction.
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