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Hemicelluloses of Ragi (Finger Millet, Eleusine coracana, Indaf-15): Isolation and Purification of an Alkali-Extractable Arabinoxylan from Native and Malted Hemicellulose B

Subba Rao, M. V. S. S. T. and Muralikrishna, G. (2006) Hemicelluloses of Ragi (Finger Millet, Eleusine coracana, Indaf-15): Isolation and Purification of an Alkali-Extractable Arabinoxylan from Native and Malted Hemicellulose B. Journal of Agricultural and Food Chemistry, 54. pp. 2342-2349.

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Abstract

Hemicelluloses (A and B) were isolated from an Indo-African hybrid variety of finger millet (ragi,Eleusine coracana) by extracting the starch-free residue with 10% sodium hydroxide under a continuous stream of nitrogen, and changes in their sugar composition during malting for 96 h were studied. Hemicellulose B, obtained in higher yield from both native (N) and malted (M) flours, was found to be completely soluble in water, richer in uronic acid, and more viscogenic than hemicelullose A. Fractional precipitation of hemicellulose B by ammonium sulfate resulted in four precipitable fractions (F-60, F-70, F-80, and F-100) and a nonprecipitable (NP) fraction varying in their yield and arabinose,xylose, galactose, and glucose contents. A progressive increase in the pentose-to-hexose ratio (P: H) from 0.42:1.0 in F-60 to 1.94:1.0 in NP was observed in native hemicellulose B fractions; however,in malted hemicellulose B the P:H ratio increased from 0.43:1.0 in F-60 to 1.56:1.0 in F-80 and then decreased to 1.13:1.0 in NP. The major fraction, F-70 (N, 44.5%; M, 38.5%), was separated into eight subfractions on DEAE-cellulose by successive elution with water, ammonium carbonate (AC) (0.1, 0.2, and 0.3 M AC), and sodium hydroxide (0.1 and 0.2 M) differing in their yield and neutral sugar composition. The purity of the major glucuronoarabinoxylan fraction (0.1 M AC eluted) was ascertained by Sepharose CL-4B, HPSEC, cellulose acetate, and capillary electrophoresis methods. A significant decrease in the molecular mass of arabinoxylan from 1200 to 1120 kDa upon malting for 96 h is an indication of cell wall degradation by the inducible cell wall degrading enzymes.

Item Type: Article
Uncontrolled Keywords: Arabinoxylans; malting; finger millet; hemicellulose
Subjects: 600 Technology > 08 Food technology > 21 Cereals > 05 Ragi (Finger Millet)
500 Natural Sciences and Mathematics > 04 Chemistry and Allied Sciences > 28 Polysaccharide Chemistry
Divisions: Dept. of Biochemistry
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 07 Apr 2007
Last Modified: 28 Dec 2011 09:27
URI: http://ir.cftri.com/id/eprint/587

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