Headspace gas analysis
Headspace gas analysis was done to ensure that the desired concentration of
gases had been attained immediately after packing, as well as throughout the
storage period. Gas samples (0.5 ml volume) were withdrawn using 0.5-ml gas-tight
Pressure-lok syringe, through silicone seals attached to the outside of each package.
Headspace gas was analysed using a Varian gas chromatograph (model 3300,
Varian Canada Inc.) fitted with a thermal conductivity detector and using a
Porapak Q (80-100 mesh) and molecular sieve 5A (80-100) columns in series.
Helium was used as the carrier gas at a flow rate of 80 ml/min. The column oven
temperature was set at 150°C, while the injector and detector temperatures were
set at 80 and 100°C, respectively. Peaks were recorded and analysed with a Hewlett
Packard integrator (model 3390A).