Results from the current study show maximum carotenoid concentrations occur in mature and fully developed kale leaves. These results are in agreement with de Azevedo and Rodriguez-Amaya (2005) who showed that lutein and β-carotene reached higher concentrations in mature kale leaves grown in Brazil. The researchers in this study identified carotenoid accumulations between two maturity levels of kale leaves, whereas five different leaf ages were evaluated in the current study. Kale leaf tissue concentrations for lutein were higher than β-carotene for all of the leaf ages sampled. Decreases in carotenoid concentrations occurred as the leaves underwent senescence. However, immature or baby kale leaves have less carotenoid concentrations than the mature leaves, and only slightly better concentrations than the senescent leaves. Harvesting kale leaves at a more mature stage of development will allow for maximum carotenoid nutritional value.
Acknowledgements
This paper was funded in part by a grant received by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 2001-52102-11254. The authors wish to thank Dr. Joanne Curran-Celentano and Dr. David Kopsell for their assistance during this project.