A flow injection analysis (FIA) system was developed for the determination of phosphate efflux from wine lactic acid bacteria (Oenococus oeni and Lactobacillus hilgardii) as an indication of cell membrane damage. The system allowed the direct injection of the cell suspension, avoiding the filtration step, with minimum sample treatment and minimized reagent consumption. The developed system is characterized by a linear concentration zone between 3.23 × 10-5 and 4.84 × 10-4 mol L-1 PO4 3- and repeatability better than 2.9%. Bacterial suspensions were exposed to a chemical stress with phenolic acids and injected in the FIA system at regular intervals. The extracellular concentration of phosphate was measured spectrophotometrically. The experimental results obtained indicate that hydroxycinnamic acids (p-coumaric, ferulic and caffeic) induced faster phosphate leakage rates than hydroxybenzoic acids (vanillic and p-hydroxybenzoic) in both strains tested, which could be related to their higher lipophilic character.