Analytical, Nutritional and Clinical Methods Section Quantitative determination of carotene stereoisomers in carrot juices and vitamin supplemented (ATBC) drinks

For the quanti®cation of aand b-carotene including the cis-isomers of b-carotene in carrot juices and vitamin supplemented (ATBC) drinks, a rapid and artefact-free method was developed. The analytical procedure involves the extraction of carotenes with a mixture of acetone-hexane and their determination by HPLC using a C30 stationary phase. No saponi®cation prior to HPLC is required. The method was applied to the determination of carotenes in commercially available carrot juices, and, for the ®rst time, in ATBC drinks. In carrot juices, a-carotene contents ranged from 19.9 to 49.4 mg/l and for all-trans-b-carotene from 32.8 to 84.8 mg/l. Relative amounts of cis-isomers, calculated as percentages of all-trans-b-carotene, were up to 16.2%. High relative amounts (31.8±44.5%) were found in ATBC drinks exclusively composed of synthetic b-carotene. In contrast, ATBC drinks containing carrot juice as a natural source of b-carotene showed signi®cantly lower isomerization (6.7±13.6%), which is in the range of plain carrot juices. Technological implications as well as nutritional consequences of these ®ndings are discussed. # 2000 Elsevier Science Ltd. All rights reserved.