Grain conditioning, also called tempering, is the controlled addition of water to grain followed by a rest period before milling, allowing the bran to toughen and the endosperm to soften for cleaner separation and more consistent flour output.
In trade practice
At the mill, wheat is wetted to a target moisture level and held in conditioning bins for a set period, which varies with wheat hardness. Harder wheats require longer conditioning times and higher added moisture than soft wheats. QA teams monitor moisture at the mill intake and after conditioning; incorrect conditioning is a leading cause of high bran contamination in flour or poor extraction rates. The conditioning parameters are normally set by the miller and are not specified in a grain purchase contract.
In a specification
Grain conditioning parameters are an internal milling process control; flour purchase specifications address the output quality indicators such as moisture, ash and protein rather than the conditioning step itself.