Fractionation and determination of chemical and physical properties of Dates’ fibers

Dates are considered as highly nutritious and healthy food. It is a rich source of DF including pectin, cellulose, hemicellulose, and lignin. The present study aims to fraction and characterize dates’ insoluble fibers to reach a better understanding of dates’ constituents. Two fractions (light and dark) were isolated from dates’ flesh together with skin fibers and their chemical and functional properties were determined. Light fiber was the major fraction in the extracted insoluble fiber; 76.22% and 59.83% in Khalas and Fard, respectively. The skin yield from 100 g dates was about 4.08 ± 0.1 g and 2.34 ± 0.04 g for Fard and Khalas varieties, respectively. The dark fiber was significantly (10 times) denser than light fiber. Water holding capacity (WHC) and oil holding capacity were significantly higher in light fiber compared to the other extracted dates’ fiber fractions as well as many reported results for other plants. TPC (bound) for the individual fiber fractions was in the range 5.12–19.87 mg GAE/100 g fiber while TFC (bound) was in the range 34.16–158.52 mg QE/100 g fiber. Using HPLC-PDA, 16 phenolic compounds were identified in dates’ fiber fractions. Protocatechuic acid (3,4-dihydroxybenzoic acid) was significantly the highest phenolic acid in all the fiber fraction, catechin was the highest flavonoid in light and dark fiber; whereas, rutin was the highest flavonoid in skin fiber. FTIR results demonstrated that dark fiber had more lignin than light and skin fiber, while sugar profile by GC–MS revealed more heterogeneity in light fibers compared to skin and dark fibers.