Polyphenol and protein extraction from rapeseed stems and leaves assisted by pulsed electric fields

Abstract

Rapeseed stems and leaves are two promising biomass feedstocks containing polyphenols, proteins, chlorophylls, and carotenoids. Reports dealing with the extraction of these valuable compounds are very rare. The biomass is composed of strong lignin layers and cellulose of high crystallinity, which should be initially treated by mechanical, thermal, or chemical methods that are commonly accompanied by many undesirable factors, such as the use of organic solvents and highenergy consumption. The application of pulsed electric field (PEF) induces electropermeabilization of cell membranes that allows acceleration of solid-liquid extraction of intracellular compounds. This chapter aims to demonstrate the positive effects of PEF treatment on the extraction of proteins and polyphenols from rapeseed stems and leaves. The PEF (5-20 kV/cm) increased significantly the extraction of polyphenols from rapeseed stems and leaves by diffusion. Treatment at 5 kV/cm resulted in the highest polyphenol purity. Compared to diffusion, PEF-assisted pressing at 8 kV/cm permitted to obtain juices with higher concentration of extractives. Moreover, a significant increase of press cake dry matter after the PEF treatment (8.8 vs. 53.0%) largely reduced energy consumption for the biomass valorization. However, the increase of plant maturity of rapeseed may require higher intensity and longer treatment time because of their more fibrous structures.