Membrane process for premium quality expeller-pressed vegetable oils

Studies were conducted with expeller-pressed groundnut and sunflower oils in a magnetically stirred flat membrane batch cell with five different types of nonporous polymeric composite membranes, to improve the oil quality. The phospholipid contents of membrane permeates of groundnut and sunflower oils were lower than 360 mg kg(-1). The maximum reductions in Lovibond yellow and red color values were 75.6 and 50% in groundnut oil, and 77.9 and 77.8% in sunflower oil, respectively. The oxidation products were rejected to the extent of 26.5-40.3%. There was an increase in tocopherol content in permeates to the extent of 34-72.2% due to preferential permeation. Negative rejection of free fatty acids (FFA) resulted in a small increase in FFA content in permeates. The results suggest that the membrane process can be used as a single-step process for the production of premium quality edible oil. However, permeate flux needs to be improved for industrial adoption. (C) 1999 Published by Elsevier Science Ltd on behalf of the Canadian Institute of Food Science and Technology. All rights reserved.