# Extraction of Galactolipids from Waste By-Products:
## 3 Results and Discussion
### Supercritical Fluid Extraction (SFE)  
In the first series of the extraction runs, nine sets of process parameters were evaluated--temperatures of 35, 55, and 75 \({}^{\circ}\)C were combined with pressures of 10, 20, and 40 MPa. None of the extraction variants was able to obtain a measurable yield of galactolipids. The possible explanation was an insufficient polarity of pure carbon dioxide; therefore, another set of experiments was conducted using ethanol as a cosolvent. The literature data highlight that higher pressures strongly improve the solvating properties of carbon dioxide; therefore, only 40 MPa was applied to limit the number of experiments [14]. Table 3 presents tested parameters and summarizes the results of this part of the work. The cosolvent flow values was selected to make up 0%, 10%, and 20% of total flow.  
The use of a cosolvent allowed the extraction of significant amounts of galactolipids and the yields obtained were in the range from 37 to 87%. The flow rate of ethanol appeared to be the crucial parameter for the process efficiency: the best results were observed for the 0.4 mL min\({}^{-1}\) share of the co-solvent, while pure carbon dioxide was unable to extract any galactolipids. The two-fold increase of ethanol content (0.2 vs. 0.4 mL min\({}^{-1}\)) resulted in improvement of the yield obtained higher than 100%; this may suggest that obtaining proper polarity of CO\({}_{2}\)-ethanol mixture may be more significant than simply adding ethanol to the system.  
The possibility of implementation of supercritical fluids for isolation of galactolipids from other matrices was reported by few teams. The paper by [PERSON] et al. described experiments on extraction of galactolipids from spinach (_Spinacia oleracea_) leaves by SFE with and without a modifier [22]. Similarly to our results, the use of pure CO\({}_{2}\) did not allow MGDG isolation, while ethanol as a cosolvent gave good results. The authors used a different matrix and tested only one parameter set; thus, full comparison of results is not possible. The work by [PERSON] et al. showed that supercritical CO\({}_{2}\) and ethanol mixture was able to extract over 80% of lipids from _Cyanobacterium Arthospira_, while pure carbon dioxide gave negligible yield [23]. The possibility of application of less orthodox solvent  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Temperature** & **Cosolvent** & **MGDGs Yield** \\ (\({}^{\circ}\)**C**) & **(mL min\({}^{-1}\))** & **(mg kg\({}^{-1}\) of Sample)** \\ \hline
35 & 0.0 & \(\leq\)0.1 a \\
35 & 0.2 & 22.7 \(\pm\) 3.1 b \\
35 & 0.4 & 48.8 \(\pm\) 2.5 c \\
55 & 0.0 & \(\leq\)0.1 a \\
55 & 0.2 & 20.9 \(\pm\) 2.5 b \\
55 & 0.4 & 49.2 \(\pm\) 2.0 c \\
75 & 0.0 & \(\leq\)0.1 a \\
75 & 0.2 & 21.4 \(\pm\) 1.3 b \\
75 & 0.4 & 47.9 \(\pm\) 1.6 c \\ \hline \hline \end{tabular}
\end{table}
Table 3: Impact of supercritical fluid extraction parameters on the efficiency of MGDGs extraction from rosehip pomace. All the experiments were performed at the pressure of 40 MPa. The letters denote statistical significance of the differences (\(p\leq 0.05\)).  
was reported by [PERSON] and coworkers, who successfully extracted galactolipids from fern fronds with dimethyl ether-water-ethanol mixture in the supercritical state [24].