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It is beyond the scope of this book to describethe technical details of the milling process.The following section only provides a briefsummary of the general operations involved inthe production of flour from wheat for readerswho are not familiar with milling.For more detailed information please refer tospecialist books, e.g. Pomeranz (1988).Milling is the process by which wheat is groundinto flour. Separating the wheat grain into itsconstituents (bran, germ and endosperm)involves the following processes (Fig. 8).

3.1 Storing

As wheat arrives in the mill it is passedthrough a cleaning process to remove coarseimpurities and is then stored according toits quality. This is mainly determined by thehardness, protein content and gluten qualityof the wheat.

3.2 Cleaning

Cleaning begins with screening to removecoarse and fine materials and the grain isseparated by size, shape and weight. Thefinished product, whole pure wheat, is thenpassed into conditioning bins.

3.3 Conditioning

Conditioning takes place before milling toproduce a uniform moisture content throughoutthe grain. Moistening helps to prevent break-up of the bran (hard outer layer) during millingand improves separation from the flouryendosperm (the mass that forms the whiteflour of the grain).

3.4 GristingAfter conditioning, different batches of wheatare blended together (gristed) to make a mixcapable of producing the required flour quality.

3.5 Milling

Essentially thi is the separation of the bran andgerm from the endosperm and the reduction ofthe endosperm to a uniform particle size(flour). This is done by a sequence of breaking,grinding and separating operations.

The quality of the wheat going into the mill,e.g. protein content, will determine the typesof flour to be produced. By blending togetherthe many different flour streams produced bythe mill, a miller can create further variationsin features such as flour colour.

3 The Milling Process

Fig. 8: Simplified diagram of the milling process(courtesy of AWB)

3 The Milling Process

N. Azudin

CLEANED

WHEAT

WHEAT-

GERM

WHEAT-

FEEDBRAN

WHITE

FLOUR

BREAK ROLLS

REDUCING ROLLS

SIEVES

SIEVES

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For example, very white flours would comefrom the early streams only, while brown floursinvolve using most streams. Wholemeal flouris produced when all the streams, bran, germand flours are blended back together withnothing removed.

3.6 References

Pomeranz Y, 1988. Wheat Chemistry andTechnology. Vol. I and II. AACC, St. Paul, MN, USA.

Milling a kernel (courtesy of Bhler AG, Uzwil)