Protein Recovery from New Zealand Oil Rapeseed (Brassica napus) Cake

The effects of downstream processing steps, lipid removal by supercritical carbon dioxide (CO2) or hexane and extraction pH on the properties of proteins extracted from rapeseed cake were investigated. The extraction pH was optimised by analysing the soluble protein profile at pH 2-11 and its effects were visualised using 1D electrophoresis. Two extraction conditions, pH 4 and pH 8, were selected for their capacity to preferentially extract the storage proteins and a wider distribution of proteins, respectively. A bottom-up proteomic analysis of the pH 8 extract identified partial matches to antimicrobial peptides from defensin-like protein 1 (DEF1) and the potential for large numbers of antihypertensive and angiotensin-converting enzyme (ACE) inhibitory peptides, previously associated with reductions in hypertension. The pH 4 and pH 8 protein extracts performed differently in the physical functionality tests. The pH 4 extracts had higher foaming capacity and stability but lower emulsion stability compared with the pH 8 extracts. Overall, the lipid removal technique used did not significantly affect the properties of proteins extracted. Graphic Abstract

Automated summary

This study investigated the effects of downstream processing steps, lipid removal techniques, and extraction pH on the properties of proteins extracted from rapeseed cake. The pH 4 and pH 8 protein extracts showed differences in physical functionality tests, with pH 4 extracts having higher foaming capacity and stability but lower emulsion stability compared to pH 8 extracts. Overall, the lipid removal technique used did not significantly impact the properties of the extracted proteins.