RAPESEED MEAL UPGRADING - PILOT-SCALE PREPARATION OF RAPESEED MEAL MATERIALS WITH HIGH OR LOW GLUCOSINOLATE CONTENTS

Because of its antinutritional factors, (high glucosinolate) rapeseed meal cannot yet be used extensively as a protein source in animal feed. The purpose of this work was to prepare, from a dehulled rapeseed meal containing 50.6 micromol g(-1) of glucosinolates (GSL), different materials for animal feed experiments. Before processing on a pilot scale, several parameters of solid-liquid extraction were studied on a laboratory scale and compared, using a calculation method based on mass balance. The results of the glucosinolate elimination showed that extraction could be conveniently performed on raw rapeseed meal with water (water to meal mass ratio of 6) at room temperature for 15-20 min. These conditions were then repeated on a pilot batch process by treating 15 kg of rapeseed meal twice with 90 kg of water. Solid residue and water extract were freeze-dried and analyzed for their glucosinolate content. The extraction procedure removed about 98% of the glucosinolates but entailed a loss of 30% of the dry matter and almost 25% of the crude protein from the initial amount of rapeseed meal. The water extract contained 168.9 micromol g(-1) of GSL and 334 g kg(-1) of protein. The solid residue contained only 3 micromol g(-1) of glucosinolates and the protein content was increased from 425 g kg(-1) (in the initial rapeseed meal) to 478 g kg(-1) (in the residue). The protein value of the processed meal is close to that of soyabean meal. Moreover an industrial use for the extract should significantly improve the economics of the process.