Ethanolic extraction of commercial rapeseed meal in the production of protein concentrate of reduced glucosinolate content

The aim of this work was to investigate suitable extraction procedures for the production of a protein concentrate of significantly reduced glucosinolate content from commercial rapeseed meal. The level is a factor in deciding its suitability for either animal or human food. Ethanolic extraction was studied as a function of time, solvent to meal ratio and solvent composition, to minimise concomitant losses of solids and nitrogen. Rapeseed meal was extracted over the range of 0 to 100% (v/v) aqueous alcohol. A concentration of 80% was found to give the best compromise between glucosinolate extraction and other component loss, but glucosinolate extraction was only about 30%. Increase of solvent polarity improved glucosinolate extractability, but extraction yields greater than 70% were not found. Subsequent extraction of the pretreated meal with water at pH 11.0 gave extracts of lower glucosinolate concentration than those made from non‐pretreated meal, but residual concentrations of the glucosinolate were unacceptable. Additional hydrolysis of the glucosinolates by exogenous myrosinase is proposed to improve extractability.