Assessing the refinement conditions for mechanical and solvent extracted hempseed oil

Authors: WILSON, PRESTON - North Dakota State University; MONONO, EWUMBUA - North Dakota State University; SARKER, NILOY - North Dakota State University; CLEMENTSON, CLAIRMONT - North Dakota State University; Evangelista, Roque; Moser, Jill

Submitted to: Journal of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/12/2025
Publication Date: 3/21/2025
Citation: Wilson, P.C., Monono, E., Sarker, N.C., Clementson, C.L., Evangelista, R., Winkler-Moser, J.K. 2025. Assessing the refinement conditions for mechanical and solvent extracted hempseed oil. Journal of the ASABE. 68(2):207-215. https://doi.org/10.13031/ja.16141.
DOI: https://doi.org/10.13031/ja.16141

Interpretive Summary: The use of hempseed oil for food and industrial applications is expanding at a rapid rate and is expected to have a global market size of USD 170 million in 2030. Industrial hempseed oil is extracted by cold-pressing methods and sold as unrefined oil. This process leaves a significant amount of oil in the cake, which can be extracted using a solvent. However, solvent-extracted oil is darker in color and has more impurities than cold-pressed oil rendering it undesirable for food and bioproduct applications. This study optimized processing methods by investigating the purity of hempseed oil obtained using several different methods. The improved refining process removed the off-flavor associated with crude hempseed oil and extends its shelf-life, thus widening its application beyond food. Expanding the demand of hempseed oil will increase the acreage for industrial hemp grain production, which in turn contributes to increased profits for farmers and producers.

Technical Abstract: Crude hemp (Cannabis sativa) seed oil is highly pigmented due to the presence of chlorophylls, carotenes, and other antioxidants, which can potentially hinder downstream processes, rendering it undesirable for food and bioproduct applications. The composition and quantity of impurities in hempseed oil are likely influenced by the oil extraction method. Therefore, this study aimed to identify the optimal chemical refining conditions for mechanical and solvent extracted oils and compare the quality of the refined oil. Crude oils were obtained through two extraction methods: cold-pressing using a Komet twin screw for mechanical extraction and solvent extracted oil using hexane in a 12 L Soxhlet extraction unit. Subsequently, the crude oils underwent degumming with citric and phosphoric acids at three acid concentrations, followed by neutralization at varying sodium hydroxide concentrations. The efficacy of the refining conditions was assessed by measuring the phospholipid and free fatty acid contents. The results revealed that the phospholipid content of the crude solvent extracted oil was ten times higher than that of the mechanically extracted oil. Consequently, the solvent extracted oil required approximately three times the amount of acid to reach the target of <15 ppm residual phospholipids. Interestingly, the type of acid used did not influence the refining process of hempseed oil. These findings suggest that the oil extraction method significantly influences the refinement process required to meet the industrial threshold of vegetable oil containing less than or equal to 15 ppm phospholipids.