AbstractBACKGROUND: Broccoli (Brassicaceae) is a rich source of phytochemicals (glucosinolates and phenolic compounds) and micronutrients (vitamins and minerals). Germinated broccoli sprouts contain much higher levels (10–100 times) of aliphatic (glucoraphanin) and indolic glucosinolates than the inflorescences. This quality characteristic of broccoli sprouts plays an important role in human health and disease prevention. Although it is known that genetic and environmental factors can affect the composition of broccoli inflorescences, the influence of such factors on the seeds and sprouts has not been widely reported. Therefore the aim of this study was to determine the effect of light versus dark growth conditions on the phytochemical composition (vitamin C, phenolic compounds and glucosinolates) of broccoli sprouts.RESULTS: Broccoli sprouts grown in the light were found to have much higher concentrations of vitamin C (by 83%), glucosinolates (by 33%) and phenolic compounds (by 61%) than those grown in the dark. During a 7 day period there was a clear and analogous trend in both treatments, with a general reduction in concentrations over time. Among the different organs studied (seeds, cotyledons, stems and roots), the cotyledons contained the highest levels of bioactive compounds, while the roots contained the lowest.CONCLUSION: Light treatment of sprouting broccoli seeds increased their concentration of health‐promoting phytochemicals, mainly during the first 3–5 days of development. Therefore the younger broccoli sprouts are a better source of bioactive compounds for the consumer than the inflorescences. Copyright © 2008 Society of Chemical Industry