Evaluation of moisture dependent geometric and gravimetric properties of small-sized sesame and black caraway seeds using image analysis

Sesame and black caraway seeds are important oil and medicinal grains that are small sized. The development of handling, processing, and storage facilities for the crops has been hampered by difficulties in measuring their geometric and gravimetric properties using Vernier caliper and micrometer screw gauge. Image analysis technique was chosen and applied in this study. Images of the seeds at different moisture levels were captured using a high resolution digital camera. The images in RGB were converted to Gray, then to Binary, and Noise was filtered, and the images subjected to threshold segmentation and analysis using LABVIEW software. Grain projected area and axial dimensions were determined. Volume was determined using liquid displacement. Dimensional analysis was used to select an appropriate grain shape as oblate spheroid. Calculated volume was obtained, and volume correction factor determined. One thousand grain mass was obtained using an electronic balance. Particle and bulk densities were determined using standard methods. Porosity was calculated using its relationship with particle and bulk densities. Results showed that as the moisture content of sesame and black caraway grains increased from 2.25% to 28.53% and 3.04% to 39.62%, respectively, the projected area, major and minor axes increased from 3.37 mm2 to 5.68 mm2, 0.3 mm to 0.452 mm and 0.287 mm to 0.45 mm (sesame), and from 1.041 mm2 to 5.136 mm2, 0.23 mm to 0.38 mm and 0.227 mm to 0.373 mm (caraway). In the above moisture ranges, volume and volume correction factor varied from 0.0214 mm3 to 0.0317 mm3 and 0.851 to 0.865 (sesame), and 0.01 mm3 to 0.0283 mm3 and 0.85 to 0.879 (caraway), respectively. W1000 increased from 2.9 to 3.875 g (sesame) and 2.644 to 3.78 g (caraway) while bulk and particle densities, and porosity decreased from 502.1 kg/m3 to 310.87 kg/m3, 828 kg/m3 to 378.4 kg/m3, and 39.4% to 17.85% for sesame, and from 560 kg/m3 to 269.8 kg/m3, 746.4 kg/m3 to 295.5 kg/m3, and 24.97% to 8.7% for caraway seed.