Following whole-grain cleaning operations, those meant to separate seeds, bran and germ from the whole grain, and to remove foreign materials via rotating drums, magnetic separators, aspirators, de-stoners, and varying additional separation methodologies, the wheat, then tempered and soaking for up to 24 hours, conditions the grain for the grinding/milling processes.
Grinding
Modern milling processes aim for a gradual reduction of the wheat kernels through a process of grinding and sifting, then blending it to meet the desired formulation of the end products. Typically the process (“Break”) will feed/inject wheat kernels from bins to roller mills (corrugated steel cylinders, paired and rotating inward against each other at different speeds), which separates bran, endosperm (starch) and germ. Typically there will be as many as five additional Breaks, where the rolls will have successively finer corrugated steel cylinders, reducing the wheat particles to granular form (middlings), which are as free from bran as possible.
Sifters
Following grinding, broken wheat particles move through a series of vibrating sifters, then shaken through a series of bolting cloths or screens, which separate the particle sizes at the cut point. Larger particles are shaken off from the top (scalped and further processed) while the fine flour sifts to the bottom. The yield will then undergo a purifying process for further removal of the bran and coarse and fine particles separation. Additional procedures, such as bleaching and enrichment, then follow.
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