3.1. Materials and Extraction of Fat from the Seeds

Blueberry, cranberry, raspberry, and cuckooflower seeds were procured from Polfeed in 2020 (Skrzyńsko, Poland), which specializes in the drying and packaging of fruit pomace resulting from the extraction of fruit and vegetable juices. Pomace with a moisture content of approximately 55% was obtained from Hortex (Skrzyńsko, Poland)), and dried on drum driers to reduce the moisture to <10%. The dried pomace was then cut and ground, and the seeds were separated. The production line (Scorpion, Poland), which included a chopper, a separator, and a pneumatic tunnel, was used to separate seeds from other parts. Before extraction, the seeds were ground in a Fritsch PULVERISETTE 25 laboratory mill (Fritsch, Kastl, Germany) with a mesh diameter of 1 × 1 mm.

The extracts from blueberry, cranberry, raspberry, cuckooflower seeds were obtained from the ground material by sonication. The extraction conditions involved the grinding of the seed samples, followed by pre-extraction with 70% ethanol at a temperature of −60 °C for 30 min. After this time as the extraction mixture reached −30 °C the sonification process was started. Since the temperature increased during the sonication process, the vessel with the extraction mixture was placed in ice. A low extraction temperature was used, following previous studies, where it was found that the optimum range for extraction of substances from stone fruit seeds is between −30 °C and −20 °C. The solution was extracted on a Hielscher Ultrasonics UP200ht sonifier (Hielscher, Teltow, Germany) for 15 min under the following conditions: 30 Ws/mL and 90 μm. After the alcoholic extracts were obtained, the solvent was evaporated under nitrogen at 30 °C. The oil layer was collected from the surface, placed in sealed dark glass tubes under nitrogen, and stored in a refrigerator at 4 °C until analysis.