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.
Okonkwo et al. (Thu,) studied this question.