Moderate electric field-assisted alkaline solubilization of lupin protein

Abstract

The nutritional quality of lupin is often limited by the presence of anti-nutritional factors (ANF), such as saponins and alkaloids, as well as anti-technological factors (ATF), including fat and polyphenols. This study evaluated the use of moderate electric field (MEF) during the protein solubilization stage as a strategy to reduce ANF and ATF and improve protein yield and the techno-functional properties of lupin protein isolate (LPI). Thus, 4 different treatments were applied during the alkaline solubilization for protein isolation purposes: (i) conventional (25 °C, 90 min), (ii) high temperature (60 °C, 45 min), (iii) MEF (60 °C, 45 min, 1200 Hz) with ON-OFF (25 V/cm) and (iv) Proportional control (up to 25 V/cm, avg 3.7 V/cm) algorithms to prevent overheating. Overall, MEF application led to a highly effective decrease in the ANF and ATF of LPI. Compared to high temperature isolation, MEF significantly lowered saponin content (1.93 g oleanolic acid/hg dm) and polyphenols (0.66 mg gallic acid/g dm). Additionally, techno-functional traits, such as water and oil absorption and foaming and emulsifying properties, were also enhanced. A prolonged voltage supply at low electric field under MEF proportional control effectively prevented overheating during protein solubilization and led to improved LPI properties when compared with ON-OFF control.