CONFLICTING EVIDENCE FOR NON-METHYL GALACTURONOYL ESTERS IN DAUCUS-CAROTA

An alcohol-insoluble residue from carrot root, analysed by an establis hed method, appeared to contain partially non-methyl esterified pectic polysaccharides. Digestion with Driselase, to which such esters are t hought to be resistant, gave small amounts of acidic oligosaccharides. Treatment with alkali at room temperature hydrolysed some of these co mponents and gave more acidic 1,4-linked oligogalacturonic acids as pr oducts. Since Driselase is known to cleave pectic methyl esters, these components appeared to contain non-methyl galacturonoyl esters. Howev er, the predominant component of this type was shown to be a monomethy l esterified, singly-acetylated tetragalacturonic acid. It was convert ed to galacturonic acid when re-treated with Driselase and, thus, was a product of incomplete digestion. Other, more minor components with s imilar properties were either other methyl esterified oligomers or wer e present in such small amounts that their characterization was not po ssible. (C) 1998 Elsevier Science Ltd. All rights reserved.