Structural, rheological and functional properties of galactose-rich pectic polysaccharide fraction from leek.

Affiliation

Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Laboratory of Biologically Active Substances, 139 Ruski Blvd., 4000 Plovdiv, Bulgaria. Electronic address: [Email]

Abstract

An acid-extracted polysaccharide from alchohol-insoluble solids of leek was obtained. The sugar composition indicated that galactose and galacturonic acid were the major sugars, followed by small amounts of rhamnose and arabinose. The fraction contained a relatively high methyl-esterified homogalacturonan next to rhamnogalacturonan type I decorated with galactose-rich side chains. The fraction consisted of three high Mw populations, covering the range of 10-100 kDa. Enzymatic fingerprinting was performed with HG/RG-I degrading enzymes to elucidate the structure. The oligomers were analysed using LC-HILIC-MS, HPAEC, and MALDI-TOF MS. The data revealed the presence of GalA sequences, having different patterns of methyl-esterification, RG-I composed of unbranched segments and segments heavily substituted with β-(1→4)-linked galactan chains of varying length. The rheological study showed the shear-thinning, weak thixotropic, anti-thixotropic, and non-Newtonian behavior of the polysaccharide. The pectin exhibited higher water holding capacity than oil-holding capacity and the fraction did form stable foams at high concentration.

Keywords

Enzymatic fingerprinting,HILIC-MS,Leek,Pectic polysaccharides,Rheology,

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