Organic acids were measured using a Synergi 4-μm Hydro-RP 80-Å HPLC column (Phenomenex Ltd., Aschaffenburg, Germany), together with a Dionex Ultimate 3000 system and a photodiode array detector (Dionex, Sunnyvale, CA) at a wavelength of 210 nm. The eluent consisted of 145 mM phosphoric acid with 10% methanol at pH 3. Elution was performed isocratically at a flow rate of 0.7 ml/min and a temperature of 20°C