# Changes in Selected Properties of Cold-Pressed Oils Induced by Natural Plant Additives
## 3 Results and Discussion
### Chemical Determination of Oils
The fatty acid composition of hemp seed oil was investigated by [PERSON] and [PERSON] [29] in terms of its application in cosmetology. No major differences were noted between the results reported by these authors and the present findings (Table 2). The authors reported 7.5% of unsaturated acids, mainly palmitic acid (5%), and a two-fold lower amount of stearic acid. Oleic acid (MUFA) accounted for 13%, and PUFAs constituted 81%, with 4% of \(\gamma\)-linolenic acid, 19% of \(\alpha\)-linolenic acid, and 58% of linoleic acid. The authors showed an n-6 to n-3 ratio of 3.3, which was 0.1 higher than the value obtained in the present study (Table 2). Thus, it can be concluded that hemp seed oil almost fulfills the requirements established by nutritionists, where the appropriate ratio of n-6 to n-3 acids in the diet should be 4:1 [27]. The growing interest in the use of natural sources of antioxidants, due to the increasing number of publications on toxicity and carcinogenicity in animals and humans, has limited the use of synthetic antioxidants [30,31]. The results of the oil extraction yield and chemical properties that indicate the quality of the extracted oils immediately after pressing are \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Fatty Acid** & \begin{tabular}{c} **Fla Seed Oil** \\ **(\(\pm\) SD) [\%]** \\ \end{tabular} & \
\begin{tabular}{c} **Hemp Seed Oil** \\ **(\(\pm\) SD) [\%]** \\ \end{tabular} &
\begin{tabular}{c} **Black Cumin Seed Oil** \\ **(\(\pm\) SD) [\%]** \\ \end{tabular} \\ \hline Palmitic (16:0) & 5.99 \(\pm\) 0.56 \({}^{\mathrm{a}}\).* & 5.02 \(\pm\) 0.47 \({}^{\mathrm{b}}\) & 12.91 \(\pm\) 0.51 \({}^{\mathrm{c}}\) \\ Stearic (18:0) & 3.62 \(\pm\) 0.14 \({}^{\mathrm{a}}\) & 2.14 \(\pm\) 0.11 \({}^{\mathrm{b}}\) & 3.03 \(\pm\) 0.16 \({}^{\mathrm{c}}\) \\ Arachidomic (20:0) & - & - & - \\ Oleic (18:1) & 17.49 \(\pm\) 0.44 \({}^{\mathrm{a}}\) & 13,23 \(\pm\) 0.39 \({}^{\mathrm{b}}\) & 23.98 \(\pm\) 0.41 \({}^{\mathrm{c}}\) \\ Linoleic (18:2) & 15.96 \(\pm\) 0.83 \({}^{\mathrm{a}}\) & 58,21 \(\pm\) 0.78 \({}^{\mathrm{b}}\) & 59.65 \(\pm\) 0.81 \({}^{\mathrm{c}}\) \\ \(\alpha\)-linolenic (\(\alpha\)-18:3) & 56.94 \(\pm\) 0.21 \({}^{\mathrm{a}}\) & 18.74 \(\pm\) 0.29 \({}^{\mathrm{b}}\) & 0.43 \(\pm\) 0.26 \({}^{\mathrm{c}}\) \\ \(\gamma\)-linolenic (\(\gamma\)-18:3) & - & 2.66 \(\pm\) 0.31 & - \\ \(\Sigma\)SFA & 9.61 & 7.16 & 15.94 \\ \(\Sigma\)MUFA & 17.49 & 13.23 & 23.98 \\ \(\Sigma\)PUFA & 72.90 & 79.61 & 60.08 \\ n-6/n-3 & 1/3.6 & 3.2/1 & 138.7/1 \\ \hline \hline \end{tabular} \({}^{\mathrm{a}}\)Values designated by the different small letters in the row are significantly different (\(\alpha=0.05\)).  
\end{table} 
Table 2: Average fatty acid composition in the analyzed oils. presented in Table 3. Although the pressing process was performed under comparable conditions, the oil extraction yield from the analyzed seeds differed significantly. The extraction yield of the flax seed oil (81.43%) was substantially higher than that of the black cumin (56.13%) and hemp (72.81%) seed oils. These differences may have resulted from the different structure and chemical composition of the seeds. The highest yield (81.43%) was obtained in the process of pressing flax seeds with moisture content of 6.64%. The oil yield was within the range of 70.1-85.7% in flax seeds with 6.1-11.6% moisture content reported by [PERSON] et al. [32]. Similarly, in their study of the effect of the method of flax seed preparation on the parameters of the pressing process, [PERSON] et al. [33] showed an extraction yield of 81.6% for the seeds with moisture content of 6.7%. The oil extraction yield for the other seeds analyzed in the present study (Table 3) was similar to the values of 72.54% and 55.49% for hemp seeds and black cumin seeds, respectively, reported by [PERSON] et al. [24]. The fatty acid composition and the presence of natural antioxidants are the most important determinants of the durability and quality of oils, which were assessed in the present study based on their AV, PV, and oxidative stability values.