Comparison of Green Technologies for Valorizing Sugar Beet Leaves (beta Vulgaris L.)

This study is focused on the valorization of sugar beet leaves (Beta vulgaris L.), a prominent by-product wasted during the process of sugar. For doing so, Ultrasound-Assisted Extraction (UAE), Pressurized Liquid Extraction (PLE), and Maceration Extraction (ME) methods were compared by evaluating the extraction yield, Total Phenolic Compounds (TPC), Total Flavonoid Content (TFC), individual phenolic profile, and antioxidant activity (e.g., DPPH, FRAP, and ABTS). Ethanol and water (70% V/V) were employed as extracting solvents. The TPC for UAE and PLE methods was 4.90±0.083 and 6.46±0.33 (mg GAE/mL), respectively, differing significantly (P<0.05) from each other. Moreover, the TFC in the PLE method was the highest with 1.45±0.06 mg QE/mL (P<0.05). The antioxidant activity of extracts was significantly different as the PLE method yielded the highest quantities. Benzoic acid was present only in the PLE extracts, while PLE and ME methods recovered the highest quantity of syringic acid (0.35±0.00 mg/L) and pyrogallol (74.80±0.01 mg/L), respectively. However, the extraction yield obtained by the UAE method (19.58±0.33%) had a significant statistical difference from other methods. Therefore, despite the higher TPC and antioxidant activity reached by the PLE method, it was proved that UAE yields higher polyphenolic compounds with a lower quantity of beet leaves.