Effect of different extraction methods on the physical and chemical properties of the following oils (sunflower - soybean - sesame)

A laboratory study was conducted from 1/9/2022 to 1/9/2023 using seeds of soybean, sunflower, and sesame plants. the aim of study the effect of two extraction methods, Soxhlet and hydraulic press. Thermal treatments on seeds before extraction, roasting, cooling, and control (without thermal treatment), on the chemical and physical properties, quality, and concentration of fatty acids in the oils of these crops. The experiment was designed as a regular factorial experiment based on the complete random design (CRD), with three factors: crop type, extraction method, and type of thermal treatment before extraction. The levels of these treatments were applied with three replications. The initial preparations, oil extraction, and chemical and physical tests were performed in the laboratories of the Department of Life Sciences/Tikrit University and the Department of Food Sciences /Mosul University, while fatty acids were diagnosed and estimated in the laboratories of the Ministry of Science and Technology in Baghdad. The results were as follows. It was observed that for the crop type, soybean recorded the highest acid value and the highest iodine value of 134 mg KOH/g, the highest density of soybean was 0.93 g/cm3. Sesame seeds recorded the highest peroxide value and the highest FFA content of 0.44%, and the highest oil refractive index of 1.475 n. While the highest saponification value was for sunflower. As for the effect of the extraction method, hydraulic pressing recorded the highest values for acid, saponification, iodine, density, and refractive index properties, reaching 4.679, 190 mg KOH/g, 123 mg KOH/g, 0.93 g/cm3 , and 1.474 n, respectively. Soxhlet extraction recorded the highest values for peroxide and FFA, reaching 3.422 mg KOH/g and 0.38%, respectively. As for the thermal treatment before extraction, roasting recorded the highest significant values for acidity, peroxide, and FFA, reaching 4.76, 3.36 mg KOH/g, and 0.39%, respectively. The control treatment recorded the highest significant rate for saponification and iodine number, reaching 124 mg KOH/g. While the cooling treatment recorded the highest significant values for density and refractive index, reaching 0.93 g/cm3 and 1.474n, respectively. As for the two-factor interactions, the interaction of crop type with extraction method showed that soybean seeds extracted by hydraulic pressing recorded the highest rates for acidity, iodine number, and density, reaching 4.74, 137 mg KOH/g, and 0.94 g/cm3, respectively. The highest rate of peroxide value for soybean seeds extracted by Soxhlet was 3.83 mg KOH/g. Meanwhile, the highest saponification rate was recorded for sunflower seeds extracted by hydraulic pressing, reaching 194 mg KOH/g. The highest FFA rate was recorded for sesame seeds extracted by Soxhlet, at 0.48%. The highest refractive index was recorded for sesame seeds extracted by hydraulic pressing, reaching 1.478 n. As for the interaction between crop type and thermal treatment, roasted soybean seeds recorded the highest significant mean for acidity value of 4.84. Roasted sesame seeds recorded the highest significant averages for peroxide value and FFA percentage of 3.71mg KOH/g and 0.48%, respectively. Soybean seeds without thermal treatment (control) recorded the highest significant mean of 138 mg KOH/g. Sesame seeds cooled recorded the highest averages for density and refractive index of 0.93 g/cm3 and 1.481 n, respectively. As for the effect of the interaction between extraction method and thermal treatment, hydraulic pressing with roasting recorded the highest acidity value of 4.82. Soxhlet extraction with roasting recorded the highest values for peroxide and FFA percentage of 3.77 mg KOH/g and 0.43%, respectively. Hydraulic pressing with control recorded the highest averages for saponification value and iodine number of 194 and 126 mg KOH/g, respectively. Hydraulic pressing with cooling recorded the highest values for oil density and refractive index of 0.93 g/cm3 and 1.481 n. As for the effect of the three-way interaction between extraction method and thermal treatment, the combined treatment of roasting and hydraulic pressing on soybean seeds recorded the highest acidity value of 4.9. Roasting and Soxhlet extraction treatment on sesame seeds recorded the highest averages for peroxide value and FFA percentage of 4.11 mg KOH/g and 0.55%, respectively. Control and hydraulic pressing treatment on sunflower seeds recorded the highest saponification value of 196 mg KOH/g. Control and hydraulic pressing treatment on soybean seeds recorded the highest iodine value of 140 mg KOH/g. The interaction between cooling treatment and hydraulic pressing on soybean seeds recorded the highest density value of 0.94 g/cm3. The interaction between cooling treatment and hydraulic pressing on sesame seeds recorded the highest value for refractive index at 1.485 n.