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

For the quantification of α- and β-carotene including the cis-isomers of β-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 saponification prior to HPLC is required. The method was applied to the determination of carotenes in commercially available carrot juices, and, for the first time, in ATBC drinks. In carrot juices, α-carotene contents ranged from 19.9 to 49.4 mg/l and for all-trans-β-carotene from 32.8 to 84.8 mg/l. Relative amounts of cis-isomers, calculated as percentages of all-trans-β-carotene, were up to 16.2%. High relative amounts (31.8–44.5%) were found in ATBC drinks exclusively composed of synthetic β-carotene. In contrast, ATBC drinks containing carrot juice as a natural source of β-carotene showed significantly lower isomerization (6.7–13.6%), which is in the range of plain carrot juices. Technological implications as well as nutritional consequences of these findings are discussed.