Pilot Scale Tannin Extraction from Chestnut Wood Waste Using Hydrodynamic Cavitation

Tannins, extracted from various plant sources, are worldwide commodities used in several different fields, including leather manufacturing and the production of bio-based adhesives, with emerging use in technical, environmental, food and feed sectors, pharmacology. Due to increasing market demand, few emerging techniques were proposed besides the conventional hot water extraction usually performed under pressurized conditions. For the first time, hydrodynamic cavitation, an emerging and straightforwardly scalable green extraction technique, was applied to the extraction of tannins from chestnut wood waste in water only and at room pressure, without any pretreatment of the raw material except for mild grinding. Promising performances were shown based on tests carried out from room temperature up to 100 ℃. Extraction rates close to 300 mg of tannin per gram of chestnut wood material (dry basis) were achieved, as well as high levels of the DPPH antioxidant activity of the obtained extract (IC50 up to about 2.45 μg of extracted tannin, corresponding to 10.8 μg of chestnut wood waste, per mL of solution). The proposed technique allows ample room for improvement with regards to process time, extraction rate and specific energy consumption, and suitable for both small-scale and industrial extraction facilities.