The metabolism of sodium nitrite by porcine skeletal muscle has been investigated in vitro under conditions relevant to the meat curing process leading to bacon and pasteurised ham, i,e. at pH 6.0 under reducing (anaerobic) conditions with nitrite at 3mM, (200 ppm). Other concentrations of nitrite were used to include the range relevant to curing ana beyond. The rate of loss of nitrite from model cures has been studied. In order to produce a 'balance sheet' of the nitrite added to model curing systems, the only stable isotope of nitrogen, [15]N, was used as a tracer. Nitrite, labelled to 96.1% with [15]N was found to be incorporated into both the non-water soluble fraction and the non-nitrite water soluble fraction of minced muscle cures. Analysis of the fractions revealed that enrichment was for the most part due to the formation of S-nitrosothiol derivatives and nitrosyImyogiobin. Analysis of the fractions also revealed the formation of nitrate, and non-volatile N-nitrosamines, the latter in concentrationsup to 2 ppm. Total recovery of the [15]N label was between 52 - 100%. Two methods of analysis of the [15]N were employed, mass spectrometry and emission spectroscopy. Analysis of the headspace gases of the model cures by high resolution mass spectroscopy confirmed the formation of nitric oxide V Volatile N-nitrosamines have been unequivocally identified by the development of two methods, both involving the use of high resolution mass spectroscopy and gas chromatography, in samples of foodstuffs preserved with nitrite prepared both commercially and in the laboratory.