Development of a Guna Seed Extractor

Abstract

Guna seed extraction presents an onerous task and has been the labour and time consuming operation that militates against the large scale production and processing of this important oil crop. To overcome this problem, a guna seed extractor that works on the principle of impact from breaker arms and macerators was developed. The seed extractor consists of a hopper equipped with flow rate control device, a seed extraction unit, winnowing unit and power system. Performance tests were conducted on the seed extractor using the fruits of two varieties of guna crop namely citrullus colocynthis and citrullus lanatus in the moisture ranges of 87.21-92.45% (wb) and 85.07-89.74% (wb) respectively, obtained by varying the fruit storage duration. Result of tests and analyses showed that the performance indicators (percentage effective seed extraction, cleaning efficiency, cleaning loss, percentage seed loss at concave, material retention and percentage seed retention) were significantly affected by fruit moisture content (storage duration), material feed rate and machine speed at 1 and 5% levels. Percentage effective seed extraction and percentage seed loss at concave increased with increase in fruit moisture content, material feed rate and machine speed Maximum percentage effective seed extraction of 95.1% at the moisture content of 92.45% for the colocynthis fruit, and 96.0% at 89.74% moisture content for the lanatus, was obtained at the material feed rate of 375 kg/h and machine speed of 939 min – 1. Maximum percentage seed loss at concave was less than 5%. Cleaning efficiency, cleaning loss and material retention in the seed extraction chamber, decreased with the increase in the fruit moisture content for both varieties of guna fruits, but increased with increase in material feed rate and machine speed, while percentage seed retention decreased with increase in moisture content, material feed rate and machine speed. Maximum cleaning efficiency of 94.15% and 91.28% for the colocynthis and lanatus varieties respectively, was obtained at the material feed rate of 375 kg/h, machine speed of 939 min -1, and fruit moisture contents of 87.21% and 85.07%. Maximum cleaning loss was less than 30% and percentage seed retention was high at low fruit moisture content, material feed rate and machine speed. Practically no seed damage was recorded. Regression models that could be used to express the relationship existing between the seed extractor performance indices and fruit moisture content, material feed rate and machine speed were established for each variety of guna crop.