AbstractThe antioxidant hydroxytyrosol has been enzymatically synthesised in order to functionalise tomato juice. The antioxidant capacity significantly increased in the functionalised juice according to a set of in vitro antioxidant assays (ie ferric thiocyanate method, inhibition of oxygen consumption, and scavenging of both DPPH· and ABTS·+ free radicals). In addition, hydroxytyrosol was stable within the tomato juice matrix under extreme storage conditions (room temperature and light exposure) for 48 days. Sensory properties (flavour and colour) of the tomato juice were not affected by functionalisation with hydroxytyrosol concentrations of up to 1 mg ml−1. Therefore this functional tomato juice could be a promising source of health‐beneficial properties, beyond basic nutrition, taking into account both the high activity and bioavailability of hydroxytyrosol.© 2003 Society of Chemical Industry