Abstract
In this study, we extracted hemicellulose from two date fruit cultivars (soft Barhi and hard Neghal) and investigated their structural, physicochemical, and thermal properties. Alkali solubilized more hemicellulose (45%-47.5%) than DMSO (6%-7%); however, DMSO preserved the feruloyl ester linkages. The monosaccharides constituent of hemicellulose includes xylose (33.1-70.6%), glucose (6.7%-17.2%) uronic acids (5.5%-13.3%), arabinose (3.2%-10.1%), galactose content (4.8%-6.8%), mannose (1.6%-3.6%), and rhamnose (0%-3.1%). The hemicellulose was primarily β-(1 → 4)-linked arabinoxylans with minor glucurono-/galacto-arabinoxylan motifs, together with insoluble glucan and pectic homogalacturonan (HG) and rhamnogalacturonan-I (RG-I). Neghal hemicellulose was structurally simpler, containing relatively less branched arabinoxylan and showing lower peak-molecular weights (27.5-35 kDa), whereas Barhi hemicellulose was enriched in arabinogalactan-protein (AGP) and RG-like features and showed higher peak-molecular weights (29.5-223.9 kDa). These structural differences correlate with a more branched, hydrated and less tightly packed hemicellulose-pectin matrix in Barhi compared with a more dominated arabinoxylan-matrix in Neghal and may contribute to the softer texture of Barhi. Overall, these results provide new insights into the composition and structural diversity of alkali-soluble hemicellulosic polysaccharides in date fruits.