Recovery of polyphenols from corn cob (Zea mays L.): Optimization of different green extraction methods and efficiency comparison
Ilaria Frosi, Anna Balduzzi, Raffaella Colombo, Chiara Milanese, Adele Papetti
Abstract
The present work focuses on the recovery of polyphenols from Lombard corn cob to develop a new upcycled ingredient. Three different green extraction methods were evaluated using an experimental design approach: a conventional extraction (CSE-HA) and a microwave-assisted extraction (MAE-HA) using hydroalcoholic solvents, and a more innovative MAE method using natural eutectic solvents (MAE-NaDES). From mathematical modelling, three optimized extracts were obtained: CBE-1 from CSE-HA (50.3% of ethanol, 60 °C, 89.9 min, and 32.7 mL/g solvent solid ratio - SSR), CBE-2 from MAE-HA (62.4% ethanol, 88 °C, 5 min, and 42.8 mL/g SSR), and CBE-3 from MAE-NaDES (20% water content, 90 °C, 5 min, and 20 mL/g SSR). The highest polyphenolic yield, reported as total metabolites content (TMC), was obtained for CBE-2 (TMC=285345.0 ± 3737.67 milli Absorbance unit per second -mAu*s), followed by CBE-1 (TMC=242965.2 ± 3411,5 mAu*s) and CBE-3 (TMC=108000.2 ± 4530.03 mAu*s). Despite NaDES still appeared as promising solvents, the hydroalcoholic mixtures gave the best recoveries; at the same time, innovative MAE showed to be a sustainable approach, providing high yield within few minutes.