Effect of degumming and bleaching on the yield and quality of epoxidized hempseed oil

Abstract:
Crude hemp (Cannabis sativa L.) seed oil (HSO) is highly pigmented with chlorophyll that is not appealing for food and industrial uses. Its high degree of unsaturation has increased its interest in many industrial applications especially the production of epoxy resin. Crude oil is usually refined to remove impurities and pigments that may affect downstream processes. Post-epoxidation refining to remove impurities and side products are very similar to the vegetable oil refining process. Therefore, this study evaluates if it is worth refining HSO pre-epoxidation and to what extent pre-refining 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 yield, oxirane, conversion, color, and other quality parameters were analyzed before and after epoxidation of HSO. Results showed that the cumulative yield of the epoxidized hempseed oil (EHSO) ranged from 63-77%, with the crude EHSO having the highest yield. The oxirane content and epoxy conversion ranged from 8.4-8.6% and 99.5%, respectively. There was a significant decrease (approximately 99%) in the color, especially chlorophyll after epoxidation for samples that were not bleached with bleaching earth. Hydrogen peroxide was very effective in bleaching the HSO. Other quality parameters did not show any significant benefit of pre-epoxidation refining of HSO. Therefore, it is recommended to directly epoxidize crude HSO.