When groundnuts are harvested they contain wide range of foreign material. This impacts quality, beginning with airflow restrictions and uneven moisture distribution during curing. Foreign material at 5 percent and above results in a deduction in the value of farmer’s stock groundnut brought to market.

During storage, foreign material interferes with airflow, reducing the ventilation that is necessary to removemoisture from the warehouse. To improve the quality of groundnuts, further modifications are needed in the threshers being used in the developing countries. Still, threshers used in India perform asatisfactory job of cleaning. The cleaning of threshed groundnut is normally done when there is no blower in the thresher or the cleaning efficiency of the thresher is low. In general most of the threshers have blowers, which perform the cleaning operation by the process of winnowing.

In the developing countries, less attention has been paid to cleaning material by the machines before storage. For the benefit of readers of this report, the cleaning operations of a typical peanut pre-cleaner and the methods to reduce the incidences of foreign material in groundnuts are displayed in Table 8.

Foreign material and loose-shelled kernels (LSK), groundnut seed inadvertently shelled by harvesting and handling operations cause problems in storage and processing (Dickens and Hutchison, 1976). LSK are often dirty, mouldy, mechanically damaged, or insect damaged. They deteriorate more rapidly during storage than in shell groundnuts. Small-shrivelled pods (raisins) contain high concentrations of moisture and often mould during storage. The incidence of foreign material in the farmers' stock groundnut may be reduced with a program of prevention and removal.

Despite the obvious advantages, most of the groundnuts are not cleaned before storage. Doing so requires a large investment in equipment and labour, provides another significant cause of breakdowns and delays during the rapid harvest season and usually results in a small loss of marketable groundnuts. Developing countries have manufactured cleaning equipment and created methods to remove some of the foreign material that segregate in storage . Cleaning with sand-screens at ground level and employing additional elevators is also an effective cleaning method. In Senegal, a rotary cleaner made by SISMAR^®, is used which can be operated by hand. This machine has a double sieve designed to separate groundnuts from husk and other rubbish. It is fitted with a large hopper, having a capacity of 80 kg (approximately one sack)plus two outlet spouts allowing the independent or simultaneous filling of two sacks. Output is 155 to 2 000 kg h^-1. The sieve axle is mounted on ball bearings. Recommended turning speed is 15 rpm, weight 212 kg.

Due to the lack of an efficient machine to shell groundnut, small farmers generally depend upon mouth shelling or employing labour to prepare seed for sowing purpose. This is a time consuming operation and does not match the shelling requirements within a limited period of time to retain seed viability. A small machine is required for this purpose, which may also meet the shelling needs of the farmers for their domestic consumption of kernels. This can also facilitate the shelling of graded kernels by the farmers instead of pods. Sale of kernels in graded quality will also fetch them more price for the produce. In Gujarat, a small manually operated sheller is available in the market for the use of small farmers and for shelling of groundnut at the time of sowing (Figure 18).

 Figure 18:Groundnut hand-sheller.