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

Abstract Interstitial concentrations of CO 2 and O 2 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 CO 2 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 CO 2 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 CO 2 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 CO 2 and O 2 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.