Carbon dioxide and cumulative heat production of canola stored under adiabatic conditions

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Pronyk, Carl William
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The main objective of this study was to measure and relate respiration and heat production of canola to its quality. Experiments were conducted under adiabatic conditions using canola (Brassica napus L.) at three moisture contents (m.c.) of 10, 12, and 14%o wet mass basis and two temperature regimes of 25 to 30 oC and 30 to 35 oC. Quality of the canola was related to levels of microflora, germination, ergosterol, and fat acidity values. Respiration data showed no difference (P > 0.05) between freshly harvested canola and canola that was dried, cooled, and stored for more than 6 months. Carbon dioxide production was dependent on storage time, moisture content, and temperature (P < 0.001) and increased with increasing levels of each. Germination was successfully modelled using CO2 production, moisture, and temperature data. Carbon dioxide production rates at the time of a drop to 95% germination were 500 (mg/d)/kg d.m. for 14% m.c., 192 (mg/d)/kg d.m. for 12% m.c., and 185 (mg/d)/kg d.m. for 10% m.c. canola between 30 and 35 oC and 290 (mg/d)/kg d.m. for 14% m.c. and 172 (mg/d)/kg d.m. for 12% m.c. canola between 25 and 30 oC. These CO2 production rates may be taken as the maximum safe rates for sound canola under the conditions described above. First signs of visible mould did not always precede a 5% drop in germination. Ergosterol levels correlated weakly with CO2 production but strongly with FAV. At ergosterol levels greater than 2 ppm germination has dropped significantly and spoilage has occurred. Cumulative heat production followed an increasing linear trend with time and moisture. Directly measured cumulative heat production was less than calculated heat production from CO2 production for carbohydrate and lipid metabolism.