Characterization of mechanically fractionated black currant pomace and its supercritical CO2 extraction products

After the process of berry juice extraction, the resulting solid residue (pomace), retains significant amounts of bioactive compounds. Unfortunately, pomace is often discarded as a waste, leading to the loss of valuable nutrients. The objective of this research was to conduct a comprehensive investigation into the chemical composition and volatile compounds found in dried black currants pomace, and to determine the changes in composition that occur as a result of supercritical CO2 extraction (scCO2E). The raw material was mechanically separated into two distinct fractions, namely the skins/residual pulp and seeds. Moisture, protein, fat, fibre, sugars and headspace volatile compounds were determined for each fraction. The scCO2E was carried out at 60 °C and 45 MPa during 120 min. The highest yield of lipids was obtained from the seeds, 15.66% and 18.29% by scCO2E and Soxhlet-hexane, respectively. Conversely, the skins yielded significantly lower lipid content, with only 4.42% and 5.21% obtained using the same extraction methods. The extraction process resulted in an increase in the percentage content of sugar, fibre and protein in the pomace after scCO2E. The volatile compounds were analysed using Headspace solid-phase microextraction (HS-SPME) coupled to gas chromatography-mass spectrometry (GC-MS). In the process of lipid extraction, a portion of the volatile compound is co-extracted and eliminated along with the extract. The extracted lipid fraction has potential applications in the food and cosmetic industries. Meanwhile, the residual defatted material still retains valuable nutrients such as proteins and sugars, rendering it suitable for downstream processes including fermentation.