Interstitial concentrations of carbon dioxide and oxygen in stored canola, soybean, and wheat seeds under various conditions

Interstitial concentrations of CO2 and O2 were measured to determine respiratory activities of microflora infecting stored canola, soybean, and wheat in different airtight storage times (1, 3 or 5 days) and at different moisture contents and temperatures (10, 15, 23, 25, 30, 35 and 40 °C). Canola seeds and ground canola with moisture contents (m.c. wet basis) of 8.0%, 10.0%, 12.0%, 13.6% and 14.0%, soybean with 23.0% m.c., and wheat with 20.3% m.c. were used. There were significant differences in CO2 concentrations between 1-d airtight storage time and other airtight storage times except at 40 °C. The same moisture content canola at the same environmental condition but in different replicates accumulated different CO2 concentrations at 10 °C and 40 °C but not at temperatures of 23 and 30 °C. Compared with the respiration of microflora, respiration by canola itself was negligible. There was no significant difference in concentration of CO2 produced by microflora within different crops at 35 °C, while there was significant difference at 15 °C and 25 °C. Values of respiration quotients (RQ) were >1 at almost any testing condition with few exceptions. Sum of CO2 and O2 concentrations were close to 21%-22% at most airtight storage times and within any crop. There was a strong positive relationship between the sum and RQ values. The sum might be used to identify whether stored grain had high level of spoiled spots with high moisture content.