Background: How to reduce the physical damage during maize kernel harvesting is a major problem for both mechanical designers and plant breeders. A limitation of addressing this problem is the lack of a reliable method for assessing kernel damage susceptibility. Previous methods of testing kernel strength lack in make a comparative discussion from the viewpoint of threshing. The design, construction and testing of a portable tool called “HANDY”, which can assess the resistance to mechanical crushing in maize kernel. A device is designed and developed that can impact the kernel with a special accelerator at a given rotating speed and then cause measurable damage of maize kernel. These factors are varied to determine the ideal parameters for operating the HANDY.
Results: Baseline testing of the HANDY is performed to determine the initial range of testing parameters. The result shows that the optimum number of test times is one for one group of maize kernels. Breakage index (BI, target index of HANDY), decreased as the moisture content of kernel increased or the rotating speed decreased within the tested range. Furthermore, the HANDY exhibited a greater sensitivity in testing kernels at higher moisture level influence on susceptibility of damage maize kernel than that in Breakage Susceptibility tests, particularly when the centrifugation speed is about 1800 rpm and the disc is curved type centrifugal disc. Considering that the mechanical properties of kernels vary greatly as the moisture content changes, a subsection linear (average goodness of fit is 0.87) to predict the threshing quality is built by piecewise function analysis, which is divided by kernel moisture. Specifically, threshing quality is regarded as a function of the measured result of the HANDY.
Conclusions: The HANDY provides a quantitative assessment of mechanical crushing resistance of maize kernel. The BI is demonstrated to be a more robust index than breakage susceptibility (BS) when evaluating threshing quality in harvesting in terms of both reliability and accuracy. This study also offers a new perspective for evaluating the mechanical crushing resistance of grains, and provides technical support for breeding maize varieties which are suitable for mechanical harvesting.