Solid-liquid extraction of polyphenols from chestnut shells: A sustainable approach for coagulant synthesis

Abstract

Shells produced during industrial chestnut processing are rich in polyphenols, offering versatile applications. Extracting polyphenols from plant sources, especially chestnut shells, is a crucial initial step in the synthesis of tannin-based coagulants. This study explores the utilization of chestnut shells for polyphenol extraction through solid-liquid extraction (SLE), with water as the solvent. The process is optimized using response surface methodology (RSM). Parameters such as extraction time, liquid-to-solid ratio, and temperature were evaluated. Key responses, including extraction yield (EY) and total phenolic content (TPC), were considered, and validated models were developed for optimization purposes. The optimal SLE conditions were 90 °C, 10 min, and 50 mL g−1, resulting in an EY of 20.3 ± 0.8%, TPC of 333 ± 23 mg-GAE/g-E, and condensed tannin (CT) of 1152 ± 68 mg-CE/g-E. Furthermore, the tannin extraction process was upscaled 10 times under the same optimal conditions, resulting in an EY of 21.6 ± 0.1% and TPC of 310 ± 15 mg-GAE/g-E. The extracts demonstrated high concentrations of condensed tannins, highlighting their potential for tannin-based coagulant production.