Quantification of cis-trans isomers of provitamin A carotenoids in fresh and processed fruits and vegetables

A polymeric 5 mu m C-30 stationary phase for reversed phase HPLC was used to separate and quantitate geometric isomers of provitamin A carotenoids in fresh and processed fruits and vegetables. beta-Carotene isomers (all-trans, 9-cis, 13-cis, and 15-cis), alpha-carotene isomers (all-trans, 9-cis, 13-cis, and 13'-cis), and beta-cryptoxanthin isomers (all-trans, 13 and 13'-cis, and 15-cis) were resolved isocratically using the C-30 stationary phase with 89:11 methanol/methyl tert-butyl ether as mobile phase. The percent of cis isomers increased 10-39% with canning. The total provitamin A carotenoid content (in micrograms per gram of dry weight of tissue) ranged from 3.5 to 907 in fresh samples and from 1.8 to 1055 in canned samples. In several fruits and vegetables, processing produced an increase of 16-50% of total measured provitamin A carotenoids relative to the fresh samples. These increases were most likely a result of increased extraction efficiency, inactivation of enzymes capable of degrading carotenoids, and/or loss of soluble solids into the liquid canning medium.