Effect of Wind Speed, Straw Walker and Sieve Conditions on Quality of Cumin Seed Cleaning

Cumin is an annual plant suitable for cultivation in dry and semi-dry lands of Iran. It is harvested in two periods to prevent seed loss. Manual harvesting either by hand or using a scythe forms the initial stage. After drying and threshing, in the final stage, the seeds are manually sieved to be cleaned and separated from foreign material. This harvesting method is time-consuming and labor intensive and causes high loss, decreasing quality and increasing seed pollution. A combine harvester was used to study the function of effective factors on the separation and cleaning of cumin seeds after threshing. The effect of independent variables (type of straw walker, wind speed, sieve blade angle, sieve angle) on dependent parameters (percent of seed loss by weight from straw walker, from cleaner system, percent of straw by weight in seed hopper) was investigated using a randomized complete block design. As the size and moisture content of cumin seed increased, terminal velocity increased. The results showed that wind speed, sieve blade angle and sieve angle had significant effects (P < 0.01) on percent of seed loss by weight in the cleaner system and percent of straw by weight in the seed hopper. The percent of seed loss in the straw walker was also affected by the type of straw walker used.