Gas Chromatographic Determination of Synthetic Antioxidants in Edible Fats and Oils - A Simple Methylation Method

YOUK-MENG CHOONG* AND HSIU-JUNG LIN

Department of Food Sanitation, Ta-Jen Institute of Technology, 20, Wei-Shin Road, Yan-Puu Hsiang, Pingtung Hsien, Taiwan, R.O.C.

(Received: March 6, 2000; Accepted: July 10, 2000)

ABSTRACT

   A simple method was developed for determining the antioxidants, BHA, BHT and TBHQ in commercial edible fats and oils. In 2-3 drops (about 60-80 mg) of an oil sample, 10% tetramethylammonium hydroxide (TMAH) methanol solution 1 mL was added and vortex-mixed for 10-minute methylation. The mixture was then extracted with 4-6 mL ether, 0.2% tetradecanol (14C-OH) 50 μL was added and thoroughly mixed. An aliquot of 0.3μL of the ether layer was then injected to GC for BHA, BHT and TBHQ analyses. The recoveries from commercial oils were in a range of 94-106%, with a coefficient of variation < 9%. Eighteen commercial edible fat and oil samples of olive, sunflower, peanut, soybean, vegetable and blend oils were analyzed using the developed method. The contents of BHA, BHT and TBHQ were found to be 0-50, 0-267 and 0-37 μg/g. Fourteen out of 18 samples were detected to contain antioxidants. The total antioxidant contents in the three blend oils ranged 259-294 μg/g, which exceeded the Chinese National Standards (CNS) control level of 200 μg/g for edible oils.

Key words: synthetic antioxidant, methylation, fats and oils, gas chromatography