The Effect of Tempering on Strength Properties and Seed Coat Adhesion Strength in Sorghum and Millet

  • EL Lazaro Department of Agricultural Engineering, Sokoine University of Agriculture, P.O Box 3003, Morogoro, Tanzania
  • JF Favier Department of Agriculture and Environmental Sciences, University of New Castle Upon Tyne, NE1 7RU, United Kingdom
  • NB Shayo Department of Food Science and Technology, Sokoine University of Agriculture


The effect of tempering on seed coat adhesion strength and mechanical strength of sorghum and millet grain kernels was investigated at different tempering durations. Tempering reduced the kernel breaking strength and had significant effect on seed coat adhesion strength. Tempering the grain for 60 minutes at ambient temperature (200C) reduced the force required to break the grain kernel from 148.4 N to 120.9 N for Dionje (a hard endosperm sorghum variety), 86 .0 N to 36.4 N for Jumbo (a soft endosperm sorghum variety) and from 51.4 N to 31.0 N for millet. The amount of energy absorbed at the breaking point of the grain kernel decreased from 52.5 mJ to 37.0 mJ for Dionje, 18.9 mJ to 13.0 mJ for Jumbo and from 14.0 mJ to 5.3 mJ for millet within the same tempering duration. Deformation at break point increased with increasing tempering duration from 0.28mm to 0.46 mm for Dionje, 0.27 mm to 0.48 mm for Jumbo and from 0.21mm to 0.35 mm for millet. Tempering for 15 minutes reduced the seed coat adhesion strength per unit area by 87.6% for Dionje, 94.7% for Jumbo and 95.7% for millet compared to untempered grain. This indicated that tempering of sorghum and millet before dehulling could reduce both the dehulling time and losses incurred during the dehulling process leading to a substantial improvement in their dehulling efficiency.
Journal of Agriculture, Science and Technology Vol.4(1) 2002: 1-9

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eISSN: 1561-7645