Neutral sugar profile of cell wall polysaccharides of pitaya (Hylocereus sp.) fruits

The composition of cell wall polysaccharides of pitaya (Hylocereus sp.) fruit pulp was studied with the aim of designing proper maceration processes for the fruit processing industry. Therefore, the degree of esterification of pectin was determined through a potentiometric titration and the consistency with a Bostwick consistometer. Moreover, the alcohol insoluble residue (AIR) was extracted and subsequently fractionated into water-, oxalate-, acid- and alkali-soluble pectins, hemicellulose and cellulose. Each fraction was analyzed for its neutral sugar composition by gas chromatography. Additionally, the AIR uronic content was measured by the m-hydroxydiphenyl (MHDP) assay. Pectin fractions in the analyzed fruit pulp were composed mainly of arabinose and galactose, while the hemicellulose fraction consists mainly of glucose, xylose and galactose. Considering the limited uronic acid content (32.3%) in the AIR and the high esterification degree of pectin, the high viscous consistency of this fruit pulp might not be highly attributed to pectin fractions.