Characteristics of carbon dioxide sorption by stored wheat

The sorption of carbon dioxide gas (CO₂) by wheat was determined in glass flasks at four temperatures (0, 10, 20 and 30 °C) and four moisture contents (m.c.) (12, 14, 16 and 18% wet basis). The gaseous concentrations were analyzed by gas chromatography and the vacuum developed from the sorption of CO₂ by wheat was measured with a mercury manometer. The calculated amount of CO₂ sorted at equilibrium was a non-linear function of both temperature and moisture content. Sorption of CO₂ by wheat decreased with increasing temperature from 0 to 30 °C at 14% m.c., and the initial rate of sorption increased with increasing m.c. from 12 to 18% at a temperature of 20 °C. Sorption was modelled using non-linear regression at two conditions (0–30 °C at 14% moisture content and 12–18% moisture content at 20 °C). The maximum mass of CO₂ sorbed in 60 h was 0.510 g/kg of wheat at 18% m.c. and 0 °C and the lowest was 0.224 g/kg at 18% m.c. and 30 °C. A linear relationship existed between the initial CO₂ concentration and the concentration after 60 h when 250 g of wheat of 14% m.c. at 20 °C was exposed in 500 ml flasks.