The digestibility of rapeseed protein isolate prepared by salt and alkali extraction: The importance of protein composition
Kangyu Li, Dengfeng Peng, Jiaqi Shao, Fenghong Huang, Weiping Jin, Xia Wan, Jack Yang, Qianchun Deng
Abstract
In this study, four rapeseed protein extracts were prepared from intact/dehulled rapeseed using salt and alkaline extraction. Their nutritional quality was assessed and linked to protein composition through 4D label-free proteomics. Salt-extracted protein isolates had lower glucosinolate (0.47 μmol/g) and phytic acid (0.59 %) content than the alkaline-extracted protein isolates, whereas the alkaline-extracted isolates demonstrated higher digestibility (93 %). The inconsistency between the trend of non-protein anti-nutritional factors and protein digestibility suggests that protein composition may play a more significant role than anti-nutritional factors. Proteomic analysis showed that both extraction methods yielded similar globulin (cruciferin) abundance, but the salt-extracted isolate contained more protein anti-nutritional factors, including albumin (napin) and other protease inhibitors. These findings highlight the importance of protein composition in determining digestibility, showing the need for a protein composition-based approach in evaluating (plant) protein digestibility. • Rapeseed protein isolates prepared by various methods vary in anti-nutritional factors and protein composition. • Protein inhibitor-like albumins, but not anti-nutritional factors, play a key role in protein digestibility. • 4D label-free proteomics is an effective tool to study protein digestibility.