Engineering properties of the cashew nut in context of designing post-harvest handling and processing machinery

Abstract

The determination of the engineering properties of the cashew nut is essential as the basis for the design and development of appropriate and optimum post-harvest handling and processing machinery. The present study examined the physical, mechanical and colour properties of cashew nuts (n = 100) at a moisture content of 7.63% (wet basis) derived from Central Java, Indonesia. The main characteristics included the length, width, thickness, mass, volume, and density. The derivative properties consisted of the geometric diameter, arithmetic diameter, surface area, frontal surface area, transverse area, shape index, sphericity, bulk density, and porosity. The mechanical properties included the static friction, static and dynamic angle of repose, and compressive load (in four orientations). It was identified that the cashew nut from Central Java was dominant with a small-medium size with an average mass of 5.42 ± 0.99 g. This cashew nut was thicker, but shorter in length than the cashew nuts from India, Nigeria, and Ivory Coast. The results of the stepwise regression analysis determined that the volume had the most substantial relationship with the mass (R<sup>2</sup> = 0.949), the bulk density had the highest correlation with the mass (R<sup>2</sup> = 0.968), and the porosity showed a high correlation with the true density and mass (R<sup>2</sup> = 0.997). The highest friction, static angle of repose, and-dynamic angle of repose occurred on the surface plywood, and the lowest was on the stainless-steel surface. In the context of designing appropriate cashew nut cracking equipment, it was recommended to provide the impact parallel to the longitudinal axis orientation due to the minimum compressive load (reduce the power requirement). Furthermore, the cashew nut colour properties of the L*, a*, b* coordinates were 35.988, 0.427, 1.718, respectively.