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A modern wheat milling machine operates with many of the same techniques that original devices used for this purpose. For centuries, humans have worked to remove the starchy inner parts of the grain, the endosperm, from its tough outer coating, the bran. This is harder than it sounds, because the bran is extraordinarily tough and can only be removed with significant force. People originally accomplished this with large grinding stones that were spun using water power. Now, the technology has been upgraded some, but the same grinding process is still used.
Before the grains arrive at the wheat milling machine, they are delivered to the facility, graded for their size, separated from metal debris, cleaned and tempered. What this means is that by the time the kernels arrive at the grinder, they are free of all inedible material and are of a desirable size. During tempering, water is added to the kernels in an attempt to soften the endosperm some. The tempering process has the opposite effect on the bran, which becomes tougher as a result. This may seem counterintuitive, but it actually makes it easier to shatter the bran and separate it from the endosperm during grinding.
Modern grinding devices are designed with a series of rollers that are spun by rotors. A wheat milling machine operates with these rollers just millimeters apart, allowing very little room for anything to pass unhindered. The rollers operate at different speeds and spin in opposite directions, pulling anything that passes through them with great force. Bulk grains are fed into these rollers, which make quick work of them. During operation, the grains are quickly crushed by the rollers, releasing the endosperm from the kernel interior. The rollers are built with food safe stainless steel surfaces that are approved by the FDA.
Even though a wheat milling machine is pretty thorough, it won’t crush everything down into flour after just one pass. In fact, the first couple series of rollers are typically used to reduce the kernels to a more manageable size. As the grains pass through the device, each series of rollers are calibrated to produce finer and finer grains of flour. After the grain passes through each set of rollers, it is directed to a powered sifter that quickly separates the flour from grain pieces that are too large for consumption. The flour is funneled to another part of the plant for further processing with a series of air pressure conveyors.
By the time the grains have been fed through all of the rollers, there will be almost nothing left of the original kernels. When the flour leaves the wheat milling machine, though, it is still not ready for consumption. White flour only consists of endosperm, so it can be sent along for purification and enrichment, but whole wheat flour requires the ground up bran and germ. Workers add these parts of the kernel back into the white flour, creating a nutritionally superior food. It’s then purified, possibly enriched, and packaged. Once packaged, it can be delivered to grocery stores and distributors all over the country.
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