Abstract
The effects of ultrasonic bleaching on chlorophyll reduction and oxidative stability of cold-pressed Cannabis sativa (hemp) seed oil was investigated using 3 different clays, Sepiolite, activated Bentonite, and an industrial clay. The chlorophyll content was significantly reduced (p<0.05) from 56.3µg/g in the untreated oil to 14.8 µg/kg, 9.9 µg/kg and 7.8 µg/kg in oils treated with Sepiolite, activated Bentonite, and industrial clay, respectively. Oxidative stability was enhanced in all ultrasonically-treated oils by a significant (P<0.05) reduction in Peroxide Value (PV) with the highest reduction (97%) observed in presence of industrial clay (PV =0.11 mEq/kg). A corresponding reduction in Conjugated Dienes (CD) was also found in the treated samples ranging from 0.073-0.095% compared to 0.102% for the control. During accelerated storage at 60 °C, increase in PVs and CDs were significantly (p<0.05) slower for the ultrasonically treated oils in the presence of clays compared to the control. Accelerated storage at 40 °C showed that the PV was 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 was enhanced by a combination of bleaching clay and ultrasonic treatment.
Practical applications: Ultrasonic treatment of cold pressed hempseed oil combined with bleaching clays proved very effective in reducing chlorophyll content. The method was not only rapid and clean but required significantly less bleaching clay. Hempseed oil treated in this way exhibited greater oxidative stability making it more attractive for industrial and consumer use. The results of ultrasonic bleaching suggested its potential for prolonging the shelf-life. Utilizing the ultrasonic bleaching technique as an alternative to conventional bleaching would be beneficial to the edible oil industry. The method is rapid, clean and requires comparatively less amount of clay.
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