Conflicting evidence for non-methyl galacturonoyl esters in Daucus carota

An alcohol-insoluble residue from carrot root, analysed by an established method, appeared to contain partially non-methyl esterified pectic polysaccharides. Digestion with Driselase, to which such esters are thought to be resistant, gave small amounts of acidic oligosaccharides. Treatment with alkali at room temperature hydrolysed some of these components and gave more acidic 1,4-linked oligogalacturonic acids as products. Since Driselase is known to cleave pectic methyl esters, these components appeared to contain non-methyl galacturonoyl esters. However, the predominant component of this type was shown to be a monomethyl esterified, singly-acetylated tetragalacturonic acid. It was converted to galacturonic acid when re-treated with Driselase and, thus, was a product of incomplete digestion. Other, more minor components with similar properties were either other methyl esterified oligomers or were present in such small amounts that their characterization was not possible. (C) 1998 Elsevier Science Ltd. All rights reserved.