Recovery of Phenolic Compounds from Rowan Fruits (Sorbus aucuparia L.): A Comparison of Pretreatment and Extraction Methods

Abstract

Phenolic compounds contribute significantly to the nutritional value of underused rowan (Sorbus aucuparia L.), but their extraction depends heavily on pre-processing and extraction methods. This study examined convective drying (CD) and freeze-drying (FD) of fruits, followed by ethanol extraction using rotor–stator homogenization, ultrasound-assisted extraction (UAE), or Soxhlet, to measure total phenolics (TPC), total flavonoids (TFC), and DPPH antioxidant activity (AA). AGREEprep benchmarking was included to assess method greenness. FD samples outperformed CD samples, increasing TPC by ≈2× (α = 0.05). For CD samples, Soxhlet extraction produced the highest averages, while for FD samples, UAE resulted in the highest AA (>58 μmol TE/g DW), and Soxhlet with 16 cycles maximized TPC and TFC (22.82 mg CGA/g DW; 4.24 mg QE/g DW). AA correlated strongly with TPC (R = 0.860) but only exhibited a moderate correlation with TFC. Multivariate analysis revealed that extracts mainly differed based on drying method and extraction intensity. AGREEprep scores were 0.45 for homogenization/UAE and 0.35 for Soxhlet. Overall, drying and extraction methods jointly influence results: FD combined with UAE offers a robust antioxidant profile with a lower environmental impact, whereas FD with Soxhlet maximizes phenolic and flavonoid yields at a higher environmental cost.