Rapeseed ( Brassica napus) Meal Valorisation through Particle-Size Fractionation: Nutritional, Antinutritional and Protein Quality Insights

Rapeseed press cake is a protein-rich oilseed co-product whose food application is constrained by high insoluble fibre, antinutritional compounds (ANFs), and sensory limitations. This study evaluated a laboratory-scale sequential workflow comprising liquid-nitrogen-assisted milling, defatting and sieving. The fine sieved defatted fraction (SDRM) contained 34.79% protein content compared with 30.00% in the original rapeseed meal (RM), with a dry-mass yield of 19.03% and a protein recovery yield of 22.07%. SDRM had the highest in vitro protein digestibility (82.92%), whereas the coarse fraction (CF) had the highest in vitro digestibility-corrected amino-acid score (98.49%). Effects on the measured ANFs were fraction-specific: CF had lower phytate (3.86 g/100 g) and trypsin-inhibitor activity (2.13 TIU/mg), whereas SDRM retained values comparable to DRM. The workflow redistributed rather than uniformly removed these compounds. Because residual hexane, glucosinolates, sinapine and techno-functional properties were not determined, the fractions should be regarded as research intermediates requiring further validation before food use.