The use of green technologies for processing lupin seeds (Lupinus angustifolius L.): Extraction of non-polar and polar compounds for concentrated-protein flour production

This study aimed to promote the valorization of lupin seeds by extracting both non-polar and polar fractions to produce a protein-rich flour suitable for food applications. Green extraction methods such as Supercritical Fluid Extraction (SFE) and SFE followed by gas-expanded liquid extraction with ethanol/CO₂ mixtures were employed. SFE yielded lupin oil with extraction yields ranging from 2.27 ± 0.02 to 4.5 ± 0.2 %, significantly influenced by temperature (40 and 60 °C) and pressure (150-350 bar). SFE extracts exhibited higher tocopherol concentration, particularly α-tocopherol (116.7-296.9 µg/g oil) and γ-tocopherol (2006-4749 µg/g oil), compared to the Bligh and Dyer (B&D) method. The fatty acid profiles were similar, although they differed slightly in composition, with the extracts obtained by SFE having higher proportions of unsaturated fatty acids (UFA) and lower proportions of saturated fatty acids (SFA). Ethanol proportion positively correlated with extraction yield (r = 0.991), resulting in higher recovery of polar lipids (PL). However, increasing ethanol percentage decreased the phenolic compounds content and antioxidant activity assessed by DPPH radical scavenging method. SFE produced lupin flour with 36 % protein content, increased by 11 % post-extraction. Ethanolic extraction also increased protein concentration, albeit less pronounced (6.8-11 % increase post-sequential extraction). Essential amino acids consistently increased post-SFE, highlighting the potential of this sustainable method to yield protein-rich flour free of non-GRAS (Generally Recognized as Safe) solvents and containing compounds essential for human health. SDS-PAGE analysis showed consistent protein profiles across all extracted flours, while FTIR assessment revealed changes in the secondary structure of proteins induced by SFE and SFE followed by gas-expanded liquid extraction processes. These findings highlight the potential of this approach to enhance the nutritional and commercial value of lupin-based products while promoting sustainable food processing practices.