# Valorization Potential of Oilseed Cakes by Subcritical Water Extraction
## 5 Conclusions  
The research provides an important contribution in chemical characterization of pumpkin, hemp and flax seed cake extracts obtained by subcritical water, since these are not available in the literature. Furthermore, the influence of specific extraction conditions, such as pressurization with different gases and homogenous catalysis, on chemical profiles of extracts is discussed. Oilseed cake extracts obtained by subcritical water demonstrated a favorable chemical composition and great biological potential. The content of all analysed compounds differed depending on the pressurisation gas and extraction conditions. In general, degradation of sample matrix constituents was more pronounced in the carbon dioxide atmosphere compared to the nitrogen atmosphere. The change in treatment conditions did not substantially affect the overall extraction yield, but affected extracts' composition. The highest extractability of lipid compounds was achieved in a nitrogen atmosphere when adding 0.05 mol/L HCl as a modifier, followed by the extraction in a carbon dioxide atmosphere. The extractability of the protein fraction was more pronounced in a carbon dioxide atmosphere. As expected, the content of proteins was the lowest in extracts obtained in nitrogen atmosphere with pure water. Protein content was comparable in a carbon dioxide atmosphere and a nitrogen atmosphere with the addition of a HCl modifier. The highest content of total amino acids (409.51 \(\pm\) 1.12 mg/100 g dry extract) was observed in hemp seed extracts obtained in a carbon dioxide atmosphere. All extracts presented high values for essential amino acids. The highest relative content of essential amino acids was observed in pumpkin seed extracts (51.49 \(\pm\) 0.47 to 58.58 \(\pm\) 0.45 mg/100 g dry extract), whereas hemp seed extracts were the richest in flavour amino acids Asp, Glu and Ala. In most of the cases, extraction in a carbon dioxide atmosphere or in a nitrogen atmosphere with a HCl modifier released more minerals into the aqueous phase. Extractability of minerals from all oilseed cakes, nevertheless, was also quite satisfactory with pure water. Further work should be conducted to study the potential bioactivity of oilseed cake extracts. Additionally, the lipid and protein fractions of water extracts should be characterized in terms of molecular-weight distribution and functional properties.  
For conceptualization, J.S.-G., S.M.; methodology, J.S.-G., S.M., C.D.-M., E.F.V. and G.S.; investigation, J.S.-G., E.F.V.; data curation, J.S.-G., S.M., C.D.-M., E.F.V. and G.S.; writing--original draft preparation, J.S.-G., E.F.V.; writing--review and editing J.S.-G., S.M., C.D.-M., E.F.V. and G.S. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Ministry of education, science and technological development of the Republic of Serbia, grant number 451-03-68/2020-14/200134 and from project 5537 DRI, Servia 2020/21-Development of functional foods incorporating a chestnut shells extract obtained by subcritical water, supported by Portuguese Foundation for Science and Technology and by FCT/MCTES through national funds. Further, this work received financial support from FEDER (through COMPETE funds), Fundacao para a Ciencia e Tecnologia (by project UIDB/50006/2020), and through FCT/MCTES--CEEC Individual 2018 Program Contract (CEECIND/03988/2018; [PERSON]). Funding acknowledgement is also given to the Italian Ministry of University (MIUR) call PRIN 2017, project 2017 LEPH3M \"PANACEA: A technology PIatform for the sustainable recovery and advanced use of Nanostructured CEllulose from Agro-food residues.\"  
The authors declare no conflict of interest.