## 4 Discussion
CSO had higher acid values when extracted with a solvent (using a Soxhlet apparatus and thermal cycles at 80 \({}^{\circ}\)C for 8 h) than when extracted via pressing (using a Komet screw press at 25 to 30 \({}^{\circ}\)C) [3]. This result could be explained by the fact that heating causes oil oxidation, which raises the acid value. The results demonstrated that high temperatures influenced the acid values. Acid values of CSO extracted by the cold solvent, pressing, and supercritical methods were 1.13 \(\pm\) 0.21, 1.18 \(\pm\) 0.06, and 1.41 \(\pm\) 0.46 mg KOH/g oil, respectively [20]. However, in the present study, none of the samples exceeded the upper limit of the acid value (4 mg KOH/g of oil) established by the Thai community product standards (Thailand Ministry of Public Health (No. 421), B.E. 2564 Issued under the Food Act B.E. 2522 on oils and fats) (Table 2). RSM prediction showed that a low temperature, lowered restriction die size, and high dry heat exposure time (i.e., low moisture content) aided in the extraction of CSO with a lower acid value (Figure 4). The experimental data indicated that die size (1 or 1.4 cm), temperature (50 or 60), and dry heat time (15 or 30 min) produced CSO with 0.80 mg KOH/g of oil (Table 2). According to the study on oil quality, the peroxide value trends for canola, corn, and sunflower oils fluctuate. This fluctuation is caused by the primary oxidation products of lipid oxidation and hydroperoxides, which are formed from unsaturated fatty acids. The initial increase in the peroxide value demonstrated a larger concentration of hydroperoxides. However, the peroxide value was reduced in the secondary oxidation products [28; 29]. The peroxide values of oil decreased with an increase in temperature under microwave treatments [30]. According to [PERSON] et al. (2020) [2], increasing the roasting temperature led to a rise in the peroxide values of CSO from 3.21 mgQ\({}_{2}\)/kg (control) to 18.42 mgQ\({}^{2}\)/kg (180 \({}^{\circ}\)C). Peroxide content was used to estimate the degree of oxidation of edible oils. Applying heat during chia seed roasting may influence the oxidation reaction, thus increasing the peroxide index of CSO [2]. CSO extracted from pretreated (water boiling, microwave roasting, oven drying, and autoclaving) chia seeds with pressing methods presented peroxide values ranging from 0.69 to 2.67 mEq/Kg oil [12]. The peroxide index values of CSO ranged from 3.12 to 8.08 mEq/Kg of oil (Table 2), which were higher than the values previously reported [31]. These changes may be associated with the cultivar of chia and processing conditions. The peroxide values of CSO extracted using the cold solvent, pressing, and supercritical methods were 0, 10.98 \(\pm\) 0.61, and 0.37 meq O\({}_{2}\)/Kg oil, respectively [20], indicating that CSO extracted via pressing had a higher peroxide value. These results indicated that the extraction methods greatly influenced the quality of CSO. However, further comparative studies are required to confirm the above statement. In the present study, none of the samples exceeded the upper limit of the peroxide index value (10.0 mEq active oxygen/kg oil) established by the Thai community product standards (Thailand Ministry of Public Health (No. 421), B.E. 2564, issued under the Food Act B.E. 2522 on oils and fats) (Table 2). Additionally, the RSM prediction showed that a high temperature would aid in the extraction of CSO with a lower peroxide value. The moisture content of the seed also affected the peroxide value, while the size of the restriction die had no effect on the peroxide value (Figure 5). The experimental data indicated that a die size of 1.2 cm, a temperature of 50 \({}^{\circ}\)C, and no dry heat treatment helped extract CSO with 3.12 mEq/Kg of oil (Table 2). The restriction die and temperature significantly affected the pressing time (Figure 5). The pressing time increased as the size of the restriction die was raised, while the pressing time decreased as the temperature was raised.