Fennel (Foeniculum vulgare Mill. subsp. piperitum) florets, a traditional culinary spice in Italy: evaluation of phenolics and volatiles in local populations, and comparison with the composition of other plant parts

BACKGROUND: Wild fennel (Foeniculum vulgare Mill. subsp. piperitum) florets are used as a typical spice in central and southern Italy. Although fennel (Foeniculum vulgare Mill.), belonging to the Apiaceae (syn. Umbelliferae) family, is a well-known vegetable and aromatic plant, whose main phytochemical compounds have been extensively analysed and investigated as flavouring agents and for their putative health promoting functions, its florets have not been specifically considered up to now. Therefore, the volatile and phenolic composition of florets from an Italian wild fennel crop was determined at different developmental stages, and compared to that of leaves and fruits. Moreover, florets of nine Italian wild fennel populations of different geographical origin from northern–central Italy were also analysed. RESULTS: The total phenolic amount increased from leaves to florets, reaching its highest value in early florets, at 58 012 mg kg−1 of dry matter (DM), then constantly decreased in fruits. In florets of wild populations, phenolics ranged from 6666 to 43 368 mg kg−1 DM. The total amount of volatile compounds was more than twice higher in florets (21 449 mg kg−1 DM) than in leaves (10 470 mg kg−1 DM), reaching its highest value in fruits (50 533 mg kg−1 DM). Estragole and trans-anethole were the main compounds of the volatile fraction. Total volatiles ranged from 24 367 to 60 468 mg kg−1 DM in florets of local populations. CONCLUSION: Significant changes in the total amount and profile of both phenolic and volatile compounds occurred during plant development. The consistent increase of estragole at later developmental stages supported the claim of different sensory properties of florets and fruits. Geographical origin significantly affected phenolic and volatile composition of wild fennel florets. © 2017 Society of Chemical Industry.