Mass and dimensional changes of single canola kernels during drying

The size and mass of individual kernels of canola (Brassica napus L.) were monitored during drying using thermo-gravimetric analysis. The test samples consisted of individual whole kernels (seeds with their seedcoat intact) and individual embryos (seeds with their seedcoat removed). The initial kernel moisture contents ranged from 1.7% to 22.6% (wet basis). The instrument was programmed to either maintain a constant temperature of 80 degrees C or increase the temperature from 25 to 105 degrees C at a rate of 5 degrees C/min. The driest test kernels (the embryo at 1.7% and the whole kernel at 2.3%) showed a net expansion during drying. The higher moisture kernels (4.3% and higher) increased in size initially followed by shrinkage as drying progressed. When exposed to constant temperature, an embryo exhibited a larger increase in size than a whole kernel. This behavior could be due to the restraining role of the seedcoat in limiting the dimensional change of the whole kernel during drying. A first order drying equation with variable radius fitted the data better than the equation with a fixed radius. (C) 1999 Elsevier Science Ltd. All rights reserved.