Kale Carotenoids remain Stable while Glucosinolates and Flavor Compounds Respond to Changes in Selenium and Sulfur Fertility

Dietary intake of certain carotenoids has been associated with reduced risks of specific cancers and chronic eye diseases. Kale (Brassica oleracea L. var. acephala D.C.) has been reported to contain the highest levels of the carotenoids lutein and -carotene among green leafy vegetable crops. Brassica vegetables also contain anti-carcinogenic glucosinolates (GS) and S-methyl-cysteine sulfoxide (MCSO) sulfur compounds responsible for flavor. In several experiments, we investigated the influence of S and Se fertility on: 1) elemental accumulation; 2) GS and MCSO production; and 3) the accumulation patterns of carotenoid pigments in the leaf tissues of kale. Plants were greenhouse grown using nutrient solution culture with a range of S and Se concentrations. Increasing S fertility increased S leaf content, but decreased Mg and Ca accumulation. Levels of GS and MSCO increased in response to increasing S in nutrient solution. However, accumulation of lutein and -carotene were unaffected by S treatment. Decreasing S and increasing Se fertility in kale production will decreases GS and MCSO compounds without affecting carotenoid pigments levels. Understanding the combined impact of fertility on flavor compounds and carotenoid pigments may help improve consumer acceptance of phytonutritionally-enhanced vegetable crops