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Molecules 2012, 17(1), 753-761; doi:10.3390/molecules17010753

Isolation and Structural Characterisation of Okara Polysaccharides

* ,
School of Food Science, Henan Institute of Science and Technology, Xinxiang 453003, Henan, China
* Author to whom correspondence should be addressed.
Received: 14 November 2011 / Revised: 18 December 2011 / Accepted: 5 January 2012 / Published: 13 January 2012
(This article belongs to the Special Issue Natural Polysaccharides: Chemistry, Bioactivity and Analysis)
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Okara is a byproduct generated during tofu or soymilk production processes. Crude polysaccharide (yield 56.8%) was isolated by removing fat, protein and low molecular weight carbohydrates from initial okara. Crude okara polysaccharide was further divided into four soluble fractions and an insoluble residue fraction by extracting with 0.05 M EDTA + NH4 oxalate, 0.05 M NaOH, 1 M NaOH and 4 M NaOH, with yields of 7.7%, 3.6%, 20.7%, 16.0% and 27.9%, respectively. Arabinose, galactose, galacturonic acid, xylose and glucose (only for the insoluble fraction) were the major constituent sugars. The primary sugar residues of okara polysaccharides were 1,4-linked β-galactopyranose, 1,5- and 1,3-linked α-arabinofuranose, 1,5-linked α-xylofuranose, 1,2-linked, 1,2,4-linked and terminal α-rhamnopyranose (or fucopyranose), and 1,4-linked β-glucopyranose (only for the insoluble fraction), indicating okara polysaccharides might contain galactan, arabinan, arabinogalactan, xylogalacturonan, rhamnogalacturonan, xylan, xyloglucan and cellulose.
Keywords: : okara; polysaccharide; structure; isolation : okara; polysaccharide; structure; isolation
This is an open access article distributed under the Creative Commons Attribution License (CC BY 3.0).

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Li, B.; Lu, F.; Nan, H.; Liu, Y. Isolation and Structural Characterisation of Okara Polysaccharides. Molecules 2012, 17, 753-761.

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