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) a nd individual embryos (seeds with their seedcoat removed). The initial kern el 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 p rogressed. When exposed to constant temperature, an embryo exhibited a larg er 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 rad ius fitted the data better than the equation with a fixed radius. (C) 1999 Elsevier Science Ltd. All rights reserved.