White flour is produced by separating the bran and germ from the wheat kernel's endosperm and then grinding the remaining endosperm into a fine powder.
Here's a breakdown of the process:
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Cleaning the Wheat: Raw wheat often contains impurities like dirt, stones, and other grains. The wheat must be thoroughly cleaned before milling.
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Tempering: This process involves adding moisture to the wheat kernels. Tempering toughens the bran, making it easier to separate from the endosperm, and also helps to optimize the milling process.
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Milling (Breaking): Traditionally, millstones were used, but modern mills use steel rollers. The wheat passes through a series of corrugated rollers that progressively break the kernel apart. The goal is to separate the bran, germ, and endosperm without crushing them.
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Sifting (Separating): After each pass through the rollers, the mixture is sifted through sieves to separate the bran and germ from the endosperm. This sifting is often done with specialized machines called purifiers and sifters.
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Grading: The remaining endosperm, now in the form of semolina (coarse particles), is further ground and sifted into different grades of white flour.
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Bleaching (Optional): Some white flours are bleached to achieve a whiter color. This can be done with chemical agents or through natural oxidation. Bleaching also affects gluten development.
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Enrichment (Optional): Since the bran and germ (which contain many nutrients) are removed to make white flour, it's often enriched with vitamins and minerals like iron and B vitamins to restore some of the lost nutritional value.
In essence, the process aims to isolate the starchy endosperm and grind it into the fine, white powder we know as white flour. The by-products (bran and germ) are often used in other food products or as animal feed.
