A COMPARATIVE STUDY TO EVALUATE THREE IMPORTANT PLANT OILS FOUND IN EGYPT

Abstract

Oils are a very important component in different diets, which makes it important for researchers to constantly search for a variety of sources of these oils that are acceptable to consumers on the one hand and are characterized by high nutritional value and storage properties on the other hand. This study was carried out to determine physical properties of linseed, soybean and walnut oils (Refractive index, color, specific gravity) as well as chemical properties (Acid value, saponification value, ester value, iodine value and peroxide value). The percentage of unsaponifiable matter and stability induction period at 100◦C were also estimated. To determine the nutritional value of these oils, both their fatty acid content (assessed by the gas chromatography apparatus) and sterol content (assessed by GC-MS). Physical properties of linseed, soybean or walnut oils showed that; refractive index were 1.48, 1.47 and 1.84, respectively, while color (red) intensity were 9.5, 3.5 and 2.6, respectively and specific gravity were 0.93, 0.92 and 0.92, respectively. On the other hand, chemical properties of linseed, soybean or walnut oils showed that; saponification value were 192, 191 and 190.73(mg KOH/g oil), respectively, while acid value were 0.87, 0.27 and 0.79 (mg KOH/g oil), respectively, and iodine value were 175, 128 and 145 (g I2/100 g oil), respectively, finally, peroxide value were 1.95, 0.77 and 1.31 (Meq oxygen/Kg), respectively. Alpha linolenic acid was the major fatty acid in linseed oil (60.21%), while linoleic acid was the main fatty acid in both, soybean oil (52.83%) and walnut oil (61.85%). β-sitosterol was the main sterol in the linseed, soybean or walnut oils (54.72, 40.13 and 76.85%, respectively). As shown by the results, the three studied oils showed high content of essential fatty acids, (both omega-3 and omega-6), making them promising oils to support diets with essential fatty acids.