Canola meal valorization via acid hydrolysis to generate free amino acids

Abstract

This study investigated an alternative approach to valorizing canola proteins by hydrolyzing them to generate amino acids (AAs). Pre-treatment of cold-pressed (CP) cake and desolventized-toasted (DT) meal with ethanol (99%, vol/vol) followed by protein separation was studied as process optimizations to maximize protein recovery with higher purity. The optimum ethanol pre-treatment conditions to achieve a meal containing less than 1% oil was reached at a meal-to-ethanol ratio of 1:4 (wt:wt) and 50°C for 30 min extraction. The protein recovery reached the maximum at pH 12 and a meal-to-solvent ratio of 1:10 (wt:vol), yielding 73% and 33% recovery from ethanol pre-treated CP and DT meals, respectively, in a single extraction. Untreated and ethanol pre-treated meals were hydrolyzed with 6 N HCl (protein-to-acid ratio of 5 mg:2 mL) for 24 h at 110°C. The ethanol pre-treatment improved AA recovery and released 373 mg AA/g dry CP meal biomass (dbm) compared to 279 mg AA/g untreated CP cake dbm. However, no improvement in AA recovery upon ethanol pre-treatment of DT meal. Sulfuric acid was examined as an alternative acid. More than 700 mg AA/g CP protein were released with 6 N H₂SO₄, while for DT meal proteins, a 10 N concentration was needed to achieve a closer value. Commercial canola meals can be utilized for generating free AAs; however, the meal processing history may affect the yield.