Valorization of date seed holocellulose through post-fermentation fractionation and functional characterization for potential food applications following rumen microbial fermentation

Date seeds, a by-product of date fruit, are an underutilized lignocellulosic polymer. In this study, seeds were ground, defatted with petroleum ether, and delignified with ethanol to obtain holocellulose (H-C). The objective of this study was to evaluate rumen-based biological fermentation combined with post-fermentation fractionation as a strategy to convert date seed holocellulose into solid and soluble fractions with potential food applications. Rumen liquor from cows was used to treat H-C, producing two fractions: residual (HSJR) and supernatant (HSJS). A post-fermentation centrifugation step was applied to obtain distinct fractions for food-related characterization. Their chemical, structural, and thermal properties were analyzed. HSJR exhibited significant changes in composition, with cellulose, protein, and fat contents of 25.0, 18.0, and 6.0 g/100g, respectively, versus 47.0, 6.0, and 0.4 g/100g in control. Solubility increased in HSJR (15.0 g/L) and HSJS (58.0 g/L) compared to the control (4.0 g/L). Thermal analysis revealed distinct glass transitions: HSJR had one (154°C), while HSJS had two (38°C, 89°C), suggesting greater heterogeneity. HSJR showed a higher melting temperature (182°C), indicating lower degradability. Morphological, thermal, and crystallinity analyses confirmed fermentation-induced structural reorganization. Overall, the results demonstrate that rumen-treated, fractionated date seed holocellulose yields functionally distinct materials with enhanced solubility (15–58 g/L), thermal stability (melting 182°C), and crystallinity (HSJS 95%). Further research is needed to evaluate their safety and sensory suitability for food applications.