# Optimizing Nigella Oil Extraction Temperature for Sustainable Production
## 3 Results and Discussion  
### Oil and Solid Components  
The results of Nigella oil samples obtained using the screw press method under five different temperatures (40, 50, 60, 70, and 80 \({}^{\circ}\)C) are presented in Table 1. The results clearly demonstrate a significant effect of temperature on the oil yield. As shown in the table, the oil yield ranged between 10.9 and 21.4%, with the lowest yield obtained at 40 \({}^{\circ}\)C and the highest at 80 \({}^{\circ}\)C. The oil yield at 40 \({}^{\circ}\)C (10.9%) and 50 \({}^{\circ}\)C (12.9%) showed no significant difference, after which it gradually increased with higher extraction temperatures up to 80 \({}^{\circ}\)C. \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Screw Press Temperature** & **Oil \%** & **Sludge \%** & **Cake \%** & **Waste in Screw and Barrel \%** & **Solid (Sludge, Cake and Waste) \%** \\ \hline Extraction at 40 \({}^{\circ}\)C & 10.9 \(\pm\) 0.8\({}^{\text{a}}\) & 3.5 \(\pm\) 0.1\({}^{\text{a}}\) & 55.5 \(\pm\) 0.6 \({}^{\text{c}}\) & 23.5 \(\pm\) 1.2 \({}^{\text{a}}\) & 82.6 \(\pm\) 0.8 \({}^{\text{a}}\) \\ Extraction at 50 \({}^{\circ}\)C & 12.9 \(\pm\) 1.1\({}^{\text{a}}\) & 3.7 \(\pm\) 0.5\({}^{\text{a}}\) & 54.3 \(\pm\) 0.6 \({}^{\text{b}}\) & 22.6 \(\pm\) 1.2 \({}^{\text{a}}\) & 80.6 \(\pm\) 1.1 \({}^{\text{b}}\) \\ Extraction at 60 \({}^{\circ}\)C & 15.6 \(\pm\) 1.3\({}^{\text{b}}\) & 3.5 \(\pm\) 0.3\({}^{\text{a}}\) & 54.0 \(\pm\) 1.5 \({}^{\text{b}}\) & 20.4 \(\pm\) 1.6 \({}^{\text{b}}\) & 77.8 \(\pm\) 1.3 \({}^{\text{c}}\) \\ Extraction at 70 \({}^{\circ}\)C & 19.0 \(\pm\) 1.7\({}^{\text{c}}\) & 3.6 \(\pm\) 0.3\({}^{\text{a}}\) & 52.5 \(\pm\) 1.3 \({}^{\text{a}}\) & 18.2 \(\pm\) 1.0 \({}^{\text{a}}\) & 74.4 \(\pm\) 1.7 \({}^{\text{d}}\) \\ Extraction at 80 \({}^{\circ}\)C & 21.4 \(\pm\) 0.8\({}^{\text{d}}\) & 3.4 \(\pm\) 0.2\({}^{\text{a}}\) & 51.8 \(\pm\) 1.7 \({}^{\text{a}}\) & 16.9 \(\pm\) 1.4 \({}^{\text{a}}\) & 72.1 \(\pm\) 0.8 \({}^{\text{d}}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Oil and solid composition in screw-pressed Nigella seeds under different levels of temperatures. Previous studies have also explored the impact of different temperatures in screw press extraction methods on oil yield, confirming significant variability ([PERSON] et al., 2018; [PERSON] et al., 2018). For example, [PERSON] et al. (2018) investigated different parameters, including screw press temperatures, and observed Nigella oil yields ranging from 8.8 to 31.6%, while [PERSON] et al. (2018) also investigated the effect of screw press temperatures on Nigella oil yield and reported its range between 15.2% to 22.7%. In the present study, an increase in yield with temperature was observed, corroborated by other studies ([PERSON] et al., 2018; [PERSON] et al., 2019). For example, [PERSON] ([PERSON] et al., 2019) reported an increase in soybean oil yield while extracting oil in screw pressed machine under a temperature between 50 \({}^{\circ}\)C to 90 \({}^{\circ}\)C; however, it decreased after then. However, the present results contrast with some other earlier reports. For instance, [PERSON] et al. (2018) applied five different temperatures (50, 60, 70, 80, 90, and 100 \({}^{\circ}\)C) to extract Nigella oil from a screw press machine (nozzle size of 6 mm, shaft screw diameter of 8 mm, rotational speed at 21 rpm) and found higher oil yields at 50 \({}^{\circ}\)C (22.7%) compared to lower yields at 100 \({}^{\circ}\)C (15.2%). They observed a decrease in oil yield with increasing the extraction temperature ([PERSON] et al., 2018). This irregular relationship between screw press temperature and oil yield may be attributed to various factors such as seed moisture content, feeding rates, applied pressure, screw press speed, restriction size, nozzle size, and shaft screw diameter ([PERSON] et al., 2018; [PERSON] et al., 2018; [PERSON] et al., 2019; [PERSON] et al., 2019). To support this, [PERSON] et al.