Abstract: Marine animal oil free of undesirable odor or taste is produced by treating a freshly killed marine animal with a peroxidase-inhibiting antioxidant, disaggregating the marine animal, separating the oil phase, mixing with a dilute aqueous acidic solution, removing the oil phase and adding antioxidant. Marine animal oil which has already turned rancid may be restored to a non-rancid state by mixing with a reducing antioxidant such as a thiodipropionate, separating out the fatty acids which have reacted with the antioxidant, preferably by column chromatography, and adding another antioxidant to prevent further peroxidation.

Abstract: To extract and purify of polyunsaturated fatty acids, particularly EPA and DHA, without cis-trans conversion, from naturally occurring oils, such as marine animal oil and various vegetable oils a mixture of free fatty acids is first extracted from the oil. The resulting mixture of pure fatty acids is then subjected to separation by means of urea complexing to remove saturated fatty acids and most mono-unsaturated fatty acids. Remaining solvent and urea are then removed from the filtrate which is then subjected to low temperature fractional crystallization in the presence of an organic solvent such as acetone. Substantially pure polyunsaturated fatty acids, especially EPA and DHA, can be separately precipitated by reducing the temperature of the filtrate in two steps. Alternatively, the volume of the filtrate is reduced in two steps and cooled to form precipitates, which are removed. The final product is a mixture of substantially pure DHA and EPA.