Cold Screw Pressing Followed by Lyophilisation Enhances Antioxidant Compound Retention in Rosehip Waste Powder

Processing rosehips generates substantial solid waste that retains valuable bioactive compounds. This study evaluated the effects of different treatments on the composition, phenolic and flavonoid contents, and antioxidant capacity of powders derived from rosehip waste. Rosehips were processed into purée by cold screw pressing or boiling, yielding raw and boiled processing waste fractions (RW and BW). These fractions were then dehydrated by hot-air drying or lyophilisation to obtain RWd, RWl, BWd, and BWl. Additionally, a previous cold screw pressing step was applied to the boiled processing waste, producing BWpd and BWpl. Cold screw pressing increased phenolic and flavonoid levels and enhanced the antioxidant capacity of the resulting waste compared with traditional boiling. The lyophilised powder derived from raw processing waste exhibited the highest total phenolic content (TPC, 27.16 mg GAE/g), total flavonoid content (TFC, 20.35 mg QUE/g), and Trolox equivalent antioxidant capacity by ABTS and DPPH (TEAC-ABTS, 89.13 µmol TE/g; TEAC-DPPH, 163.99 µmol TE/g), although at higher processing costs. As hot-air drying achieved comparable levels for TPC (20.01 mg GAE/g), TFC (19.53 mg QUE/g), TEAC-ABTS (58.01 µmol TE/g), and TEAC-DPPH (150.01 µmol TE/g), it may represent a more economical alternative to lyophilisation. These findings demonstrate the potential of rosehip-processing waste as a sustainable raw material for the development of functional food ingredients.