Influence of moderate electric field pretreatment on protein extraction from lupin flour

Abstract

Lupin protein quality is notably affected by the presence of anti-nutritional factors (ANF) such as polyphenols, alkaloids and saponins, along with anti-technological factors (ATF) like polyphenols and fat. This research addresses the impact of moderate electric field-assisted (MEF) pretreatment on lupin flour (LF) prior to protein extraction by isoelectric precipitation, focusing on its effects on ANF and ATF content, protein yield and techno-functional properties. Pretreatments were carried out for 3 min using water and ethanol–water (1:4 v/v), under two conditions: (i) conventional mechanical stirring (952 rpm) and (ii) MEF (from 150 to 300 V) at 60 °C. Pretreatment decreased noticeably ANF and ATF content of both LF and lupin protein isolate (LPI). Furthermore, it yielded a lupin protein concentrate (LPC, avg. 62 g protein/100 g) with reduced levels of ANF and ATF. LF pretreatment increased the recovery of protein (avg. 12 %). Compared to conventional pretreatment, MEF application reduced fat (avg. 21 %), saponins (avg. 37 %), polyphenols (avg. 38 %) and antioxidant activity (avg. 8 %) and improved LPI's techno-functional properties, including water and fat absorption index (avg. 17 and 68 %, respectively), foaming (avg. 122 %) and emulsifying properties (avg. 10 %). The LPC fraction also exhibited promising characteristics, indicating its potential as a valuable ingredient in food formulations. These findings highlight the effectiveness of MEF pretreatments as a strategy for reducing ANF and ATF, enhancing protein extraction and overall quality.