Valorization of sugar beet leaves: optimizing ultrasound-assisted extraction of bioactive substances and proteins

Sugar beet leaves, an underutilised by-product rich in proteins and polyphenols, were investigated for recovery of bioactive compounds using ultrasound-assisted extraction (UAE). Response Surface Methodology was applied to identify optimal conditions. The model predicted a maximum Bradford protein yield of 92.07 mg/g d.m. and a total flavonoid content (TFC) of 5.18 mg quercetin eq./g d.m. at 9 min, 100% amplitude, and a 1:50 solid-to-liquid ratio. Under the same conditions, the experimental values reached 94.6 mg/g d.m. (Bradford protein) and 4.71 mg quercetin eq./g d.m. (TFC), showing good agreement with predictions. Extraction time, amplitude, and ratio significantly affected Bradford protein yield, while amplitude was the only significant factor for TFC. In contrast, no significant effects were observed for total phenolic content or Lowry protein yield. These findings highlight the potential of UAE as a sustainable method for valorising sugar beet leaves into high-value natural products.