Cereals processing technology

3
Wheat, corn and coarse grains milling
W. G. Owens, Satake Centre for Grain Process Engineering,
University of Manchester Institute of Science and Technology
3.1 Introduction
The term ‘coarse grains milling’ is a very broad one that refers to the comminution
of the berries of the wheat, barley and other coarse grain crops. This is
the definition of milling as interpreted by an engineer or process manager.
However, a cereal chemist or quality assurance manager might interpret the term
milling as the transformation of raw material into a primary product for
secondary processing. This definition encompasses every aspect of the
transformation, from raw material purchasing to quality assurance and product
testing. However, this definition is too broad to discuss in the context of a
chapter such as this. Moreover, many of these subjects are discussed
exhaustively in related and other texts. Instead this chapter will focus on the
engineering perspective of the development of the milling industry.
In many cases milling is a very simple process, involving the use of a simple
grinder to create a specific particle size distribution from the bulk raw material.
The opposite end of the spectrum is the complex process employed to produce
white flour for the baking industry. In between these two extremes lies the whole
spectrum of milling processes. These include milling for the brewing industry
and milling for the breakfast cereal industry among others.
The wet milling process employed by some starch manufacturers is a
considerable departure from most other processes encountered, because of the
introduction of large quantities of water to the process, with the result that the
product of the process is a liquid and not a powder. This process is a very
specific one and will not be discussed in this chapter. However significant detail
is entered into in the book Corn, Chemistry and Technology, published by the
American Association of Cereal Chemists (Watson and Ramsted 1984). The