Novel method and machine for dehulling of guar seeds and optimisation of dehulling process

Abstract

Traditional guar processing method to produce guar gum splits comprises of splitting, germ separation, heating and dehulling heated splits through cutting and scratching in which 12–17% endosperm are lost. A novel pretreatment method and machine was developed to dehull guar seeds prior to splitting. The process involved steeping seeds in ethanol solution (0.2–0.4% concentration), conditioning for 5min followed by dehulling through compressive- shear- and abrasive-forces applied simultaneously using the developed machine. The machine comprised of hopper, feed regulator, under-runner discs of wire mesh for dehulling pretreated seeds, and aspirator to separate hull. Pretreated guar seeds moved between discs in compressed condition, thus subjected to abrasive and shear forces to remove hull. Dehulling efficiency increased with moisture content and rotational speed up to 75.8±1.7% (d.b.) and 90rpm, respectively and then decreased. Second order polynomial model described the relationship between dehulling efficiency, moisture content and rotational speed. Process conditions were optimised using surface plot and contour plot. Optimum range of moisture content and peripheral speed were 74–80% (d.b.) and 2.76–3.2ms−1 (88–102rpm), respectively at which a dehulling efficiency of 91.67±5% was observed with 3.48% split formation. Capacity of the machine was 80kgh−1 pretreated seeds at 90rpm.