Effect of Degumming and Bleaching on the Yield and Quality of Epoxidized Hempseed Oil

Crude hemp (Cannabis sativa L.) seed oil (HSO) has a high degree of unsaturation, which has increased its interest in many industrial applications, especially epoxy-resin production. Crude HSO is refined to remove impurities and pigments; however, refining after epoxidation (post-epoxidation refining) also removes impurities and side products, similar to the vegetable oil refining process. Therefore, this study evaluates if it is worth refining crude HSO before epoxidation (pre-epoxidation), and to what extent pre-refining (before epoxidation) is needed to maintain yield and quality. Crude, degummed, and bleached HSOs were epoxidized at 60 °C for 5.5 h using amberlite 120H+ solid catalyst. The cumulative recovery yield, oxirane, conversion, color, and other quality parameters were analyzed before and after epoxidation of HSOs. Results showed that the recovery yield pre- and post-epoxidation of the epoxidized hempseed oils (EHSOs) ranged from 74 to 85%, with the bleached EHSO having the lowest yield. The oxirane content and epoxy conversion ranged from 8.4 to 8.6% and 99.5%, respectively. There was a significant decrease (approximately 99%) in the chlorophyll color content after epoxidation for samples that were not bleached initially with bleaching earth. Hydrogen peroxide was very effective in bleaching the HSO. Other quality parameters did not show any significant benefit from pre-epoxidation bleaching of the HSO. Therefore, it is recommended to directly epoxidize crude HSO or degummed HSO.