Thermal Characteristics and Proton Mobility of Date-Pits and their Alkaline Treated Fibers

Thermal characteristics and proton mobility of date pits and their alkaline-treated fibers were measured by differential scanning calorimetry (DSC) and low-field nuclear magnetic resonance (LF-NMR). The DSC thermogram of date pits showed three endothermic peaks: first one for oil melting, second one after glass transition, and third one for the solids-melting and a shift indicating glass transition. The residue from the alkaline-treated fibers (F1) showed an exothermic peak and an endothermic peak for solids-melting. The exothermic peak before solids-melting indicated that more molecular order was progressed in the fibers before its melting. The exothermic shift could be due to the crystallization or molecular ordering in the sample and the endothermic peak was due to the solids-melting. The precipitated alkaline-soluble fibers (F2) at a medium pH (i.e., 5.5) showed mainly solids-melting, while precipitated fibers (F3) at very low pH (i.e., 1.5) showed an absence of glass transition and solids-melting. The residue fibers and fibers precipitated at pH 5.5 were mainly crystalline, while precipitated fibers at pH 1.5 were non-crystalline rigid amorphous. However, the precipitated fibers at pH 1.5 showed less structural bonding between the crystallites as compared with the precipitated fibers at pH 5.5. The three pools of proton were identified in the date pits, and these were linked to the protons in the lignin, holocellulose (i.e., cellulose and hemicellulose), and oil. The protons in the fibers F1, F2, and F3 as a function of temperature varied differently, which indicated structural diversity of the fibers. Therefore, fibers having different structural characteristics could be developed from the date pits.