English abstract
Date-pits are by-products of date-processing factories and its utilization could bring economic gain. Date-pits need to be pre-treated to enhance their functionality for proper utilization. Four types of fibers were prepared by alkaline digestion of defatted date-pits followed by acid digestion, which were pre-treated with water, ethanol, microwave and pressure cooker. Defatted date-pits were considered as control. The moisture content of the fibers was varied from 1.33 to 2.25 g/100 g sample. Ethanol pre-treated fibers showed the highest content of hemicellulose (21.8 g/100 g sample), hollo-cellulose (i.e. 76.1 g/100 g sample) and the lowest content of lignin (0.8 g/100 g sample). Pressure cooker sample gave the lowest content of hemicellulose (12.7 g/100 g sample) and highest level of lignin (5.6 g/100 g sample). In general, all pre-treated samples showed higher cellulose content as compared to the defatted date-pits.
Thermal analysis of the defatted date-pits showed a structural change at -5.3oC fol-lowed by a glass transition shift, onset at 135oC and solids melting-decomposition en-dothermic peak at 183oC with enthalpy of 125 kJ/kg. In addition, a small endothermic peak was observed after glass transition. Similarly, other treated fibers showed lower temperature structural change, glass transition and solids melting-decomposition. However, all treated fibers showed an exothermic peak (i.e. varied 155-160oC) before the solids melting-decomposition, which were considered as cold crystallization due to molecular ordering. There was no significant difference of the glass transition tem-peratures for the defatted and other fibers, while ethanol pre-treated sample showed highest specific heat change (i.e. 380 J/kg oC). This indicated that ethanol treated fibers contained highest fraction of amorphous component. The water pre-treated fibers showed lowest solids melting-decomposition peak temperature at 173oC, with an enthalpy 227 kJ/kg, while ethanol pre-treated fibers showed highest solids melting-de-composition peak (i.e. 187oC) and enthalpy (239 kJ/kg). Higher enthalpy indicated higher molecular networks, thus more energy needs to be applied to decompose.
Fourier Transform Infrared (FTIR) spectra showed the molecular structure of the defat-ted date-pits and other prepared fibers. The peaks at different wave numbers were used to characterize the functional groups in the fibers. Spectrum of the defatted date-pits showed significantly lower absorption indicating lower structural damage. The higher absorption peaks in the cases of prepared fibers indicated higher molecular structural breakage, which could allow the fibers to interlink with other components while used in different products. The characteristics of the prepared fibers could be used to determine their suitability while incorporating in different foods and bio-products.
