Reduction of Chlorophyll in Cold-Pressed Hemp (Cannabis sativa) Seed Oil by Ultrasonic Bleaching and Enhancement of Oxidative Stability

The effects of ultrasonic bleaching on chlorophyll reduction and oxidative stability of cold-pressed Cannabis sativa (hemp) seed oil is investigated using three different clays, Sepiolite, activated Bentonite, and an industrial clay. The chlorophyll content is significantly reduced (p<0.05) from 56.3 mu g g(-1) in the untreated oil to 14.8 mu g kg(-1), 9.9 mu g kg(-1), and 7.8 mu g kg(-1) in oils treated with Sepiolite, activated Bentonite, and industrial clay, respectively. Oxidative stability is enhanced in all ultrasonically-treated oils by a significant (p<0.05) reduction in Peroxide Value (PV) with the highest reduction (97%) observed in the presence of industrial clay (PV = 0.11 mEq kg(-1)). A corresponding reduction in Conjugated Dienes (CD) is also found in the treated samples ranging from 0.073-0.095% compared to 0.102% for the control. During accelerated storage at 60 degrees C, increase in PVs and CDs are significantly (p<0.05) slower for the ultrasonically treated oils in the presence of clays compared to the control. Accelerated storage at 40 degrees C shows that the PV is greater in hempseed oil bleached with Sepiolite clay compared to a combination of Sepiolite and ultrasonic bleaching. Based on these results it is evident that the rapid removal of chlorophyll from cold pressed hempseed oil is enhanced by a combination of bleaching clay and ultrasonic treatment.