Bleaching of Color Fixed Cottonseed Oil

Abstract

Six varieties of bleaching agents: Commercial, Engelhard and Tonsil bleaching earth, magnesium oxide, aluminum oxide and charcoal were selected to evaluate their abilities on reducing color and gossypol content of color fixed neutralized cottonseed oil. Color of this oil was higher than 50 red units / 20 yellow using Lovibond Tintometer and 1 inch cell and its gossypol content was 200 ppm . The bleaching of the color fixed cottonseed oil was carried out by using two methods, conventional method (stirring oil with bleaching earth), and passing the oil on column filled with bleaching adsorbents. The aluminum oxide showed a superior adsorption capacity in reducing color to less than 1.4 red/20 yellow and reducing the gossypol content to 21 ppm, by using the column system. The conventional method failed to reduce the color of the treated samples therefore, alkaline pretreatments were conducted. The treatment of color fixed oil with alkaline solution (sodium hydroxide solution 14.5 Be o or sodium silicate at 45 Be o ) followed by conventional Engelhard bleaching earth treatment reduced the color of oil to values lower than 1.4 Red/20Yellow.