Hexane defatting effects on rapeseed protein extractability and properties at neutral and mild pH 8.5

Abstract

Rapeseed is a promising plant protein source yet to be fully explored. Traditionally, rapeseed proteins are extracted from hexane-defatted press cake at high alkaline conditions to maximise protein recovery. Instead of the traditional approach, this study explored the effects of extracting proteins from the whole-kernel seed, focusing on assessing the hexane defatting process followed by gentle protein extraction at neutral pH compared with pH 8.5. Extraction at neutral pH resulted in a napin-rich protein extract, while alkaline conditions favoured cruciferin extraction as expected. Hexane defatting destroyed the oil bodies's structure while detaching the cell membrane from the cell wall, causing dehydration, and enabling interactions between the seed constituents. Increasing cycles of hexane treatment greatly reduced the total protein recovery by 9 g/100 g under neutral pH and >60 g/100 g under mild alkaline conditions which affected the protein structure, leading to a more rigid structure with a slightly higher melting temperature.