Influence of canola seed dehulling on the oil recovery by cold pressing and supercritical CO2 extraction

Abstract

Dehulling canola seeds provides an enriched cake in oil and proteins leading to an improved meal quality after oil extraction. The aim of this work was therefore to explore the impact of dehulling pre-treatment on both oil recovery and quality, using cold pressing followed by supercritical CO2 extraction. For this purpose, whole canola seeds, dehulled seeds, and reconstituted mixtures of 5% and 10% hulls were used to recover canola oil. After 1 h pressing, the obtained results showed that the lowest oil yield (≈37%) was obtained using dehulled seeds, indicating that dehulling adversely affects the efficiency of cold pressing. After pressing, remaining oil in press cake was extracted by supercritical CO2. After process optimization, the optimal parameters providing the maximum extraction yield (≈74%) were found at 40 °C temperature, 35 MPa pressure, 8.5 kg/h CO2 flow, and 10 min of conditioning. Using these conditions for grinded seeds, the combined process allowed a quasi-total oil recovery (95 ± 3%) and showed similar oil quantities extracted from either whole seeds, dehulled seeds, or reconstituted mixtures, demonstrating thus the efficiency of the proposed process. On the other hand, total phenolic compounds content in oil was reduced upon dehulling, and results show that the oil obtained by supercritical CO2 extraction was about twice enriched in phenolic compounds when compared to that obtained by mechanical pressing.