Onion rind (dry onion skin) was obtained during onion production (farm located next to Skierniewice, Poland). The rind was chipped into 0.2–0.5 cm fragments using a mechanical crusher. The apple and strawberry pomace were obtained from the factory producing fruit juice (Agropol Company, Potycz) in a form of dry, small pieces (0.1–1 cm). The rapeseed meal was used as the commercial product (Ardex Company, Sochaczew).