Optimization of Rapeseed Protein Preparation by Salt Extraction and Its Physiochemical Properties

The aim of the study was to provide a reference basis for the preparation of high-quality rapeseed protein by salt-extraction. Cold-pressed dehulled rapeseed meal was used. The salt-extraction process was optimized using single-factor experiment and response surface experiments analysis, and the physicochemical properties were investigated and compared with the protein obtained by alkali-extraction and acid-precipitation. The results showed that the optimal conditions were as follows, pretreatment with phytase and hydrated ethanol, 0.75 mol/L CaCl₂ extracting medium, pH6.5, solid-liquid ratio 1:12 g/mL, temperature 53 ℃ and extraction time 90 minutes, and achieving a protein solubility of 27.96% under these conditions. Furthermore, the resulted rapeseed protein achieved a higher protein purity at 77.12%±0.63% and a lower phytic acid content of 0.13%±0.01%, in comparison to the protein obtained by alkali-extraction and acid-precipitation method. What's more, SDS-PAGE analysis revealed that the main components of salt-extracted protein were albumin. Its higher contents of α-helices and β-turns dominated its stable and flexible structure, also leading to better solubility. This experiment provides a basis for using the salt-solution method to prepare high-quality rapeseed protein.