SPECTROPHOTOMETRIC DETERMINATION OF LIMONIN IN ORANGE JUICE

Limonin in navel orange juice was extracted twice with dichloromethane. The combined extracts were treated with acid-washed alumina and filtered, and the alumina was washed with chloroform. Combined dichloromethane and chloroform extracts were evaporated and the residue was partitioned between acetonitrile and petroleum ether. Limonin in the acetonitrile layer was determined by treatment with alkaline hydroxylamine followed by addition of acid ferric perchlorate solution and measurement of the absorbance of the solution at 510 mμ. This method was useful for determining limonin in the 5- to 40-p.p.m. range, and the results correlated well with the bitterness of navel orange juice. It was not satisfactory for orange peel, twigs, leaves, roots, or for grapefruit juice, because of interference from coumarins. © 1968, American Chemical Society. All rights reserved.