The New Life Of Exhausted Bentonite From The Grape Processing Industry: From Waste To Precious Resource To Produce Novel Raw Materials Enriched In Polyphenols

Introduction: In an ever-growing perspective of circular economy, the development of conscious, sustainable and environmental-friendly strategies to recycle the waste products is the key point1. The exhausted bentonite, from the grape processing industries, could become a precious matrix to produce new pharmaceutical/cosmetic excipients enriched in functional polyphenols2. Materials & Methods: The exhausted bentonite recovered after the fining process (supplied by Bono&Ditta s.p.a., Campobello di Mazara TP, Italy) was stored at -20°C. Solid-liquid extractions on both freeze-dried and as-collected (wet) bentonite were carried out by using PEG200 or propylene glycol as solvents. The liquid extracts were evaluated in terms of yield, pH, total phenolic (Folin-Ciocalteu) and protein (Bradford) contents, antioxidant power (DPPH) and amount of representative polyphenols (HPLC-DAD). Results: Both solvents extracted significant amounts of polyphenols from the waste bentonite, leading to coloured fluids characterized by acidic pH after water-dilution. Among all, the best extract was obtained from wet bentonite treated with PEG200 as it highlighted the highest phenolic content and consequently the strongest antioxidant activity. Conclusion: The waste bentonite emerged as a valuable source of functional polyphenols, and it could be treated with such solvents currently used in the pharmaceutical/cosmetic field to directly obtain novel enriched raw materials and excipients.