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ABSTRACT Resolution of cis‐trans alpha‐ and beta‐carotene isomers was achieved using a rapid (30 min) high‐performance liquid chromatography method employing a slurry‐packed calcium hydroxide column. The isomers found in fruit and vegetable products were identical to those formed through iodine catalyzed isomerization of carotene solutions. A survey of fresh and commercially processed fruit and vegetable products indicated that the greatest percentage of isomers was found in processed foods (20.1–54.0%). Of the fresh products surveyed, cis‐isomers were found in plums, nectarines and peaches, and no cis‐isomers were detected in sweet potatoes, carrots and tomatoes; however, all fresh green vegetables contained from 19.6–28.3% monocis‐isomers.
Chandler et al. (1987) studied this question.