Professor University of Saskatchewan Saskatoon, Saskatchewan, Canada
Canola, the second largely produced oilseed in the world, provides oil and protein-rich meal. Industrial-scale canola oil extraction involves solvent extraction and de-solventizer toasting steps resulting in extensively modified meal proteins with compromised nutritional and functional attributes. Cold-pressing has less impact on meal protein and generates cold-pressed meal (CPM), but the high residual oil content (~15%) pose challenges in aqueous protein extraction. Objectives of this study were to investigate; 1) extraction with ethanol to obtain low-oil CPM (E-CPM), 2) determining the suitability of E-CPM for protein and fibre fractionation using AAFC process, and 3) characterization of protein fractions of E-CPM. Hexane extracted CPM (H-CPM) was investigated as the control. Optimization of extraction conditions to reach the lowest oil content in CPM was studied according to Box-Behnken design. Extraction condition combination of no water in ethanol, 1:4.5 (w:v) meal:solvent, 1.75 h extraction time and 25℃ extraction temperature reduced ~90% of CPM oil. Repeated extraction under same conditions produced E-CPM with 0.2-0.5% oil and 41% protein while H-CPM had 0.2% oil and 35% protein. Both meals generated five fractions with different protein levels. Protein content of napin, cruciferin, intermediate, soluble sugar and seed coat fractions were 95.2%, 56.7%, 26.4%, 16.5%, 30.5% for E-CPM and 94.5%, 54.7%, 22.4%, 16.3%, 35.1% for H-CPM, respectively. Phenolic compounds of the meals were 1.25 and 1.42 mg/g of E-CPM and H-CPM, respectively. The napin-rich, cruciferin-rich and seed coat fractions of E-CPM and H-CPM contained phenolic compounds between 0.43 and 0.79 mg/g. The oil and water holding capacities of napin-rich fractions were different than cruciferin-rich fractions and showed a variation between the meals they derived from. Use of ethanol at room temperature removed oil and phenolic compounds of CPM and had minimum effect on protein extractability. E-CPM can be fractionated into napin- and cruciferin-rich fractions similar to H-CPM.