The present invention relates to a process for preparing zeaxanthin and/or biosynthetic intermediates and/or secondary products thereof by culturing genetically modified plants which, compared to the wild type, have a reduced .epsilon.-cyclase activity caused by double-stranded .epsilon.-cyclase ribonucleic acid sequences, to the genetically modified plants and to the use thereof as foodstuffs and feedstuffs and for producing carotenoid extracts.