Phenylacetic acid in vinegar

An off-flavor compound isolated form vinegar was identified as phenylacetic acid by gas chromatographic acid by gas chromatographic retention time and mass spectra of the isolated and authentic reference materials. The sensory odor threshold level of phenylacetic acid was 0.5ppm by direct test and 0.1ppm by remaining test in 4.5% acetic acid solution. The concentration of phenylacetic acid measured by HPLC was 2.5_??_8.2ppm in commercial vinegars. The phenylacetic acid at this level of concentration probably influenced the off-flavor of the vinegar.