Quantitative determination of carotene stereoisomers in carrot juices and vitamin supplemented (ATBC) drinks

For the quantification of alpha- and beta-carotene including the cis-isomer s of beta-carotene in carrot juices and vitamin supplemented (ATBC) drinks, a rapid and artefact-free method was developed. The analytical procedure i nvolves the extraction of carotenes with a mixture of acetone-hexane and th eir determination by HPLC using a C-30 stationary phase. No saponification prior to HPLC is required. The method was applied to the determination of c arotenes in commercially available carrot juices, and, for the first time, in ATBC drinks. In carrot juices, alpha-carotene contents ranged from 19.9 to 49.4 mg/l and for all-trans-beta-carotene from 32.8 to 84.8 mg/l. Relati ve amounts of cis-isomers, calculated as percentages of all-trans-beta-caro tene, were up to 16.2%. High relative amounts (31.8-44.5%) were found in AT BC drinks exclusively composed of synthetic beta-carotene. In contrast, ATB C drinks containing carrot juice as a natural source of p-carotene showed s ignificantly lower isomerization (6.7-13.6%), which is in the range of plai n carrot juices. Technological implications as well as nutritional conseque nces of these findings are discussed. (C) 2000 Elsevier Science Ltd. All ri ghts reserved.