Grain cleaning is the mechanical removal of dust, straw, weed seeds, broken kernels, stones and other foreign material from harvested grain, and is essential for protecting downstream milling equipment and meeting import quality standards.
In trade practice
Cleaning lines typically combine rotary or flat-bed sieves to separate by size, aspirators to remove light material by airflow, and destoners to separate dense foreign objects. In Ukrainian export practice, the degree of cleaning is reflected in the impurity and foreign-matter figures recorded on the grain quality certificate issued at the point of loading. Buyers specifying grain for milling should confirm whether the contracted impurity limits apply before or after cleaning at the origin elevator, as this affects the usable yield. Inadequate cleaning before storage is a common cause of elevated mycotoxin risk, because damaged kernels and organic debris accelerate mould growth.
In a specification
A grain purchase contract should state maximum permitted levels for total impurity, weed seeds and foreign matter separately, reference the sampling and analysis method to be used, and specify whether limits apply to the bulk lot or to the average of multiple samples.