Sacha inchi oil (SIO) extraction has been extensively studied using various oil extraction techniques to achieve a high oil recovery. However, most studies relied on heat-based methods, which led to compromised oil quality and reduced nutritional values, particularly polyunsaturated fatty acids (omega-3 and omega-6), vitamin E, and phenolic compounds. To address these concerns, this study employed a hydraulic cold-pressed extraction (HCPE) technique for extracting SIO aiming to enhance oil yield while preserving its nutritional integrity. During the HCPE process of sacha inchi seeds (SIS), conducted at a constant temperature of 25 ± 1 °C, pressures and pressing times were varied within the range of 30–50 MPa and 10–30 min, respectively, to determine their impact on SIO yields. The results revealed that both pressure and pressing time significantly influenced the yields of SIO (p < 0.05), with the highest oil recovery of 86.31 wt.% on a wet basis achieved at 50 MPa for 30 min. Regarding physicochemical properties, the peroxide values (5.71–9.07 meq/kg), iodine values (176.22–197.76 g I₂/100 g), acid values (1.82–2.16 mg KOH/g), and percentage of free fatty acids (0.91–1.08 wt.% as oleic acid) were found to be influenced by pressure and pressing time (p < 0.05). Additionally, the color variation by L* (34.22–35.17), −a* (0.39–0.81), and b* (3.48–5.62) changed with each oil yield. Notably, the high iodine value in SIO indicated a substantial content of polyunsaturated fatty acids, including omega-3 (40.86%), omega-6 (40.87%), and omega-9 (10.20%). Furthermore, a comparison with solvent extraction methods demonstrated that HCPE exhibited similar efficiency in extracting SIO, offering additional advantage in terms of its cold-pressed condition, eliminating of solvent use, simplicity, short extraction time, and higher oil recovery.

The conventional solvent extraction (CSE) method is commonly used to extract oil from oilseeds. Even though the extraction of oil from soybean seeds using the CSE method has been studied extensively, the application of response surface methodology (RSM) has not yet been widely explored. In this paper, the CSE method was employed using three different types of solvents – ethanol (Eth), n-hexane (Hex), and a mixture of Hex:Eth in a ratio of 2:1 – and optimized using RSM to extract the oil from Cambodian soybean seeds. For each solvent, a central composite design (CCD) was applied to optimize the extraction conditions, such as the extraction times (15, 30, and 45 min) and solvent-to-solid ratios (5:1, 10:1, and 15:1 mL/g). This CCD generated 11 experimental runs for each type of solvent. The optimum oil yields when using ethanol, Hex:Eth, and n-hexane were 20.53%, 18.78%, and 17.39%, respectively. The optimum condition was obtained at 15 min extraction time and 15:1 (mL/g) solvent-to-solid ratio for all solvent types. The coefficients of determination of ethanol, Hex:Eth, and n-hexane were 0.9710, 0.9954, and 0.9263, respectively, which mathematically indicated a good model for the prediction. Therefore, the model was considered accurate and reliable for predicting oil yields in this study.

The objective of this study was to investigate the effects of hydraulic pressing conditions on the extraction yields of Cambodian soybeans using hydraulic press machine. The extraction of soybean oil through hydraulic pressing is a chemical-free mechanical method that involves the compression of the soybean seeds using heat and pressure. The different pressures (30, 40, and 50 MPa) and pressing times (15, 20, 25, 30, 40, 50, and 60 min) were performed on the extracted soybean oil yield. The physicochemical properties and fatty acid profiles of the extracted soybean oil were also analyzed. The physicochemical properties such as peroxide value, iodine value, acid value, and color were determined by AOAC methods. And the fatty acid profiles, including linoleic acid, oleic acid, linolenic acid, palmitic acid, and steric acid, were characterized by gas chromatography with a frame ionization detector. The results demonstrated that the highest yield of 12.49% was achieved at a pressure of 50 MPa and a pressing time of 60 min. The crude soybean oil obtained exhibited acceptable physicochemical quality and fatty acid profiles. The fatty acids of soybean oil were found to be rich in unsaturated fatty acids, with 52.69% of linoleic acid and 25.24% of oleic acid. However, it is important to note that this study has limitations, and further research should investigate additional factors, particularly the effect of temperature in hydraulic pressing, to optimize oil yield.