Kernel and bulk density changes due to moisture content, mechanical damage, and insect damage

Danping Guo, Purdue University


Corn (Zea Mays), is one of the major grain crops in the world and moisture content, mechanical damage and insect damage are three factors that affect its quality. The primary goal of this thesis was to investigate the effects of moisture content, mechanical damage and insect damage on kernel and bulk density of corn. The study was conducted using two corn hybrids, Pioneer 1352 and Pioneer 1221, that were grown on Purdue Agronomy Farm for Research and Education (ACRE), manually picked and shelled. In Objective 1, the effect of three different moisture conditioning processes (drying from harvest moisture, rewetting from 30% to 10%, and rewetting to 30% before drying from 30% to 10%) on kernel and bulk density was investigated. In Objective 2, the effect of mechanically damaged kernels at various damage percent levels created by blending undamaged whole kernels with damaged kernels was investigated. Objective 3 investigated the effect of insect damage, both artificially simulated internal damage by drilling a hole per kernel and actual insect damage by infesting with Sitophilus zeamais (maize weevil) was investigated. For Objective 1, in all three moisture conditioning processes, both kernel and bulk density were found negatively and linearly correlated to moisture content. In general, Pioneer 1221 had a higher kernel and bulk density than Pioneer 1352 for all moisture conditions. A comparison of the last two conditioning processes (rewetting from 10% to 30% and drying from 30% to 10%) showed that neither kernel density nor bulk density was significantly different. Additionally, comparisons of the data from this research and the empirical models by Nelson (1980) and Brusewitz (1975) showed agreement at either the low moisture or high moisture of each hybrid. As mechanical damage level increased, the kernel density changed positively, and the bulk density changed negatively. For the artificially induced insect damage by drilling a hole per kernel, kernel density increased and bulk density decreased as artificial damage level increased. However, for the actual insect infestation treatments, the kernel density at different life stages of Sitophilus zeamais decreased in the larva and pupa stages and this trend reversed at the adult stage. Comparisons of the data with the control (un-infested kernels) seem to indicate that the internal infestation was the cause of this decrease. Further work need to be conducted in order to better explain the results and verify whether kernel density can be used as a distinguishable indicator of internal insect infestation in corn kernels.




Ileleji, Purdue University.

Subject Area

Agricultural engineering

Off-Campus Purdue Users:
To access this dissertation, please log in to our
proxy server