English abstract
Value added products, such as roasted date-pits powder, and date-pits oil, could be developed from date-pits byproducts from whole dates. In order to develop quality products, it is important to understand the structural characteristics of date-pits. In this project, the chemical composition and thermal characteristics of un-roasted and roasted date-pits were measured. The moisture content of roasted pits powder was 1.63% (wet basis) and soluble solid in water-extract was 6.57%. Protein, fat, ash, carbohydrate, and crude fiber were found 6.96, 7.95, 0.96, 61.50, and 21.00%, respectively. Carbohydrate is the main solid component of date-pits. The amount of total sugars was 2.93%, while reducing and non-reducing sugars were 1.09% and 1.84%, respectively. Fatty acid analysis indicated that lauric acid (C12) and oleic acid (C18:1) were the major fatty acids in roasted date seeds, followed by palmitic acid (C16) and linoleic acid (C18:2). With regards to mineral content, potassium (K) was the highest followed by phosphorus (P), magnesium (Mg), calcium (Ca), sodium (Na), and iron (Fe). Other minerals were less than 10 mg/kg sample, while lead (Pb), cadmium (Cd), and chromium (Cr) were at trace levels. The melting point (peak of the endotherm) and latent heat of melting of pure date-pits oil were found to be 1.8°C and 68.1 J/g, respectively. Thermal analysis was conducted for roasted, un-roasted and defatted date-pits powder using Differential Scanning Calorimetry (DSC) and Modulated Differential Scanning Calorimetry (MDSC). The heating thermogram showed an endothermic peak (for ice and/or fat melting) and no evidence of glass related processes within the temperature range of –90 to 80°C. The endothermic peak for the lower moisture sample was mainly due to the melting of relatively bound lipids in the matrix since all water in the sample was un-freezable. The missing of a glass transition could be explained by the fact that the date pits contained a high ratio of low-mobility ordered regions to amorphous domains. This would enhance strong interactions and a percolation effect (clustering) between adjacent sequences, thus rendering free-volume effects insignificant within the accessible temperature range. The roasted sample with fat showed higher un-freezable water of 29.4%, while the other samples showed lower values; 22.2 - 23.9%.
