الملخص الإنجليزي
Date-pits are considered as waste and value added functional food components could be developed. One of the important value added components could be oil from date-pits. In order to utilize it as cooking or frying oil, it is important to measure its characteristics and oxidative stability during storage. Date-pits contained moisture, protein, fat, fiber, ash and total carbohydrate as 4.1,6.1, 9.2, 0.92, 31.3 and 79.7 g/100 g date-pits. It also contained significant amount of important minerals. Calcium was the highest (2994 ppm), followed by potassium (1712 ppm), magnesium (687 ppm), selenium (456 ppm), iron (14.8 ppm) and zinc (10.19). Date-pits oil showed a low refractive index (1.450) with density 876.5 kg/m and polyphenols as 22.0 mg/100 g oil. Thermal characteristics of date-pits oil measured by MDSC showed oil crystallization by an exothermic peak during cooling and an endothermic peak during heating. The melting (i.e, non-reversible) showed two peaks and onset at -32.0°C, maximum slope at - 10.0°C, peak at -0.3°C, end at 19.6°C and total enthalpy of 60.0 kJ/kg. The onset, mid and end of glass transition were - 12.1, -10.4, and -7.8°C, respectively with a specific heat change 308 J/kg K at its transition. Date-pits oil contained six major fatty acids (i.e. C18:1, C18:2, C18:0, C16:0, C14:0 and C12:0); oleic fatty acid (C18:1) is the highest level (47,5%). In this study the oxidative stability of Omani date-pits oil was studied during storage at different temperatures (30, 100 and 150°C). The saturated fatty acid increased while the unsaturated fatty acids (mono and polyunsaturated) decreased significantly with increase of storage temperature and time (p<0.05). The reduction of linoleic acid (C18:2, w6) was much higher (i.e. 90.0%) than the reduction of oleic acid (C18:1, w9) (i.e. 27.0%) due to the increased sensitivity of C18:2 to oxidation. Oxidation parameters (AV, PV and PAV) increased significantly with the increase of storage time and temperature (p<0.05). Considering free fatty acid, it was observed that date-pits oil had relatively good oxidative stability at low temperature (i.e. 30°C) at least 90 days as maximum storage time used in this study. However, its acceptability remained up to 49 days of storage at 100°C, while it was 28 days during storage at 150°C. Based on the fatty acid composition and oxidative stability of date pits oil, it could be used as edible cooking oil. In addition, it could be used in pharmaceutical, cosmetic and other non-food industries.
