## 3 Results and Discussion
### Thermal Behavior of Algal Pigment Microparticles  
For more detailed analysis of the obtained microparticles, structural transitions in the microparticles were obtained by the PGSS process using the DSC and TGA methods at temperatures ranging from 25-900 \({}^{\circ}\)C. The thermogravimetric change of algae pigment  
Figure 4: Environmental scanning electron microscope (ESEM) photographs of polyethylene glycol microparticles of pigments of raw algal materials or extracts obtained with different extraction techniques: (**A**) raw algae material; (**B**) supercritical CO\({}_{2}\) extraction; (**C**) ethanol/water extraction; (**D**) conventional extraction.  
microparticles was compared with the PEG to evaluate the thermal stability of the obtained microparticles (Figure 5). The desorption peak that would be assigned to algae pigment extract was not detected in the thermogram of microparticles. Lower onset melting temperature in the case of SCO\({}_{2}\)E and the absence of an extract endothermic melting peak indicate that the extract was a disrupted PEG crystalline structure. The melting enthalpy (\(\Delta\)Hm) was very similar to carrier enthalpy for extracts obtained with conventional extractions (WAT and CON), while that for RAM was significantly lower. However, the melting enthalpy (\(\Delta\)Hm) increased when SCO\({}_{2}\)E was encapsulated, which indicates the higher thermal energy storage capacity of microparticles (Table 2).  
The thermograms of the microparticles showed a characteristic peak at around 60 \({}^{\circ}\)C of the PEG [26], without an extract peak indicating that the extract was completely encapsulated into a carrier during DSC measurement. The samples' thermogravimetric curves  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \(\mathbf{T_{On}}\) (\({}^{\circ}\)C) & \(\mathbf{T_{n}}\) (\({}^{\circ}\)C) & \(\mathbf{\Delta H_{n}}\) (\(\mathbf{/g}\)) & \(\mathbf{T_{Onax}}\) (\({}^{\circ}\)C) & \(\mathbf{T_{max}}\) (\({}^{\circ}\)C) & \(\mathbf{\Delta H_{max}}\) (\(\mathbf{/g}\)) \\ \hline
**RAM+PEG** & 45.47 & 63.59 & 181 & 382.53 & 411.64 & 101.17 \\ \hline
**SCO\({}_{2}\)E+PEG** & 37.47 & 60.44 & 191 & 372.77 & 408.90 & 222.81 \\ \hline
**CON+PEG** & 46.36 & 62.01 & 173 & 370.49 & 413.86 & 188.07 \\ \hline
**WAT+PEG** & 48.65 & 60.26 & 171 & 372.12 & 410.87 & 250.85 \\ \hline \end{tabular}
\end{table}
Table 2: Summary of thermal properties of algae microparticles.  
Figure 5: DSC (Differential scanning calorimetry (DSC) and TGA (thermogravimetric analysis) of PEG microparticles of pigments of raw algal materials or extracts obtained with different extraction techniques: Sample 2: RAM+PEG—raw algal material, Sample 5: SCO\({}_{2}\)E+PEG—extract obtained with supercritical extraction, Sample 6: CON+PEG—dry extract obtained with conventional extraction, Sample 7: WAT+PEG—dry extract obtained with ethanol/water extraction, PEG—polyethylene glycol.  
followed a consistent pattern, and Figure 5 shows that the microparticles exhibit a thermal decomposition that begins in the temperature range between 180 and 280 \({}^{\circ}\)C, and ends at temperatures above 430 \({}^{\circ}\)C. These microparticle thermal characteristics are comparable to those reported for PEG 4000 by [PERSON] et al. [27] and [PERSON] et al. [28].