Impact of Preservation Techniques on Polyphenols in Aronia melanocarpa Pomace and Their Recovery by Optimized Accelerated Solvent Extraction

The valorization of agro-industrial by-products is of increasing importance within circular economy strategies. Aronia melanocarpa pomace, a by-product of juice production, represents a valuable source of polyphenols with potential applications in food, nutraceutical, and cosmetic formulations. This study aimed to evaluate the effect of different preservation methods on the polyphenolic composition of Aronia pomace and to optimize accelerated solvent extraction (ASE). Pomace samples were subjected to drying, freeze-drying, freezing (−18 °C), and deep freezing (−80 °C). UAE was applied as a rapid screening method for polyphenol extraction, while ASE was used as an advanced technique for efficient recovery of target compounds. ASE parameters, including temperature (40–120 °C), methanol concentration (40–100%), and number of extraction cycles (1–3), were optimized using response surface methodology (RSM) based on a Box–Behnken design. Qualitative and quantitative analyses were performed using UHPLC–MS and HPLC–DAD. The developed models were statistically significant (p < 0.01) with high coefficients of determination (R2 = 0.88–0.97). Temperature had a positive effect on phenolic acid extraction but negatively affected anthocyanins due to thermal degradation. Optimal extraction conditions differed between compound groups: phenolic acids were maximized at 120 °C and 75% methanol (two cycles), while anthocyanins required milder conditions (82 °C, 92% methanol, three cycles). Moreover, our study showed that drying significantly reduced the content of several compounds, particularly anthocyanins, whereas low-temperature methods had minimal impact. The results highlight the importance of tailored extraction strategies and support the sustainable utilization of Aronia pomace as a source of bioactive compounds.