Intensification of lupin protein solubilization using high-power ultrasound

Lupin's nutritional value can be reduced by anti-nutritional factors (ANF), including alkaloids and saponins, as well as by anti-technological factors (ATF), such as fat and polyphenols. This study investigated the use of high-power ultrasound (HPU) during alkaline solubilization of lupin flour with the aim of reducing ANF and ATF while enhancing protein yield and techno-functional properties of lupin protein isolates (LPI). For that purpose, the influence of time (15-30-45 min), temperature (30-45-60°C) and HPU amplitude (0-50-100%) was assessed. The impact of lupin flour (LF) addition to the alkalinized water and temperature on the ultrasonic field was evaluated from frequency spectra analysis. HPU enhanced lupin protein solubilization at elevated temperatures, resulting in higher extraction and protein yields (avg. 6 and 3%, respectively), compared to conventional alkaline solubilization without HPU at 60°C. This effect was consistent with the temperature-dependent cavitation behavior observed in LF dispersions. In addition, HPU also reduced the content of fat (avg. 47%), saponins (avg. 10%) and polyphenols (avg. 17%), and enhanced techno-functional treats, including water absorption (avg. 23%), foaming stability after 2 h (avg. 68%), emulsifying activity index (avg. 18%) and emulsifying stability index (avg. 119%), compared to non-sonicated conditions. High-amplitude HPU application (∼100%), combined with elevated temperatures (∼60°C) and prolonged solubilization times (∼45 min) were identified as the most suitable conditions to enhance protein recovery and techno-functional properties while reducing undesirable components. These results indicate that HPU-assisted solubilization represents a promising and efficient strategy for the sustainable production of high-quality LPI suitable for industrial applications.