AbstractTraditional methods for the quantitation ofO‐acetate ester and pyruvic acid acetal in xanthan gums require hydrolysis procedures followed by determination of acetic acid and pyruvic acid separately either by colorimetric, enzymic or chromatographic assays. Some of these assays are time‐consuming and involve many solvent extractions, and during the course of these procedures the xanthan sample is destroyed by hydrolysis. The methyl protons of bothO‐acetate ester and pyruvic acid acetal can be detected by1H n.m.r. spectroscopy, and this paper describes a method for the quantitative determination of these groups on intact polymeric xanthan using an internal integration standard dissolved within the sample. The method is non‐destructive, can be easily performed on a 60MHz spectrometer equipped with Fourier Transformation and variable temperature control, and simultaneously quantitates bothO‐acetate ester and pyruvic acid acetal with improved