6 ry Milling Technology Introduction In milling processes involving both separation The single term milling,,applied in the con and size reduction the two operations may be carried out in two distinct phases, as in sorghum text of cereals, covers a wide range of processes. milling, or, to some extent, combined, as in In general they are methods of transforming bread- and soft-wheat milling, where the two whole grains into forms suitable for consumption or for conversion into consumable products processes continue throughout the multi-stage Milling processes peration(although e ei phasis changes as the intentional heating, although in some cases, as n process proceeds). In rice milling, two stages es involve oat processing, a heating phase precedes the occur but neither seeks to fragment the endo- milling, and in maize dry milling a drying phase sperm. The first stage removes the husk and the is included second removes the bra Characteristic(but not essential) features of Even the above distinctions are not absolute as milling processes are processes are in use for decorticating wheat grains before reduction of size and some rice is milled 1. Separation of the botanical tissues of the grain Into flour. It is clear that few generalizations can (e.g. endosperm from pericarp, testa and be made about cereals milling, most milling embryo technologies depend upon a series of individual 2. Reduction of the endosperm into four or grits. processes through which stocks pass in sequence Some milling systems include both operations Milling processes (e. g. white flour milling from wheat), while others The processes are of three types, they may involve only one(e.g. rice milling comprises only separation, and wholemeal wheat milling seeks 1. Change the shape and size of the feedstock only to reduce particle size 2. Separate fractions produced by (1)-type Milling schemes are conveniently classified treatments wet or dry, but this indicates a difference in 3. Change the temperature and/or water content degree rather than an absolute distinction as water of the stocks is used in almost all separations. Damping or tempering' features even in 'dry' milling; it is The processes are described below considered in detail in Ch 5 as it is a pre-milling Treatments that change shape and size treatment. This chapter is concerned with so called dry milling; wet milling processes are dealt Abrasion with in Ch. 12. Emphasis is placed on preparation for human consumption but the term milling Effects depend upon severity, thus also applies to production of animal feeds. A brief 1. Surface abrasion is a relatively gentle process description of feed-milling is given in Ch. 15 which removes all or part of the fruit coats6 Dry Milling Technology Introduction The single term ‘milling’, applied in the con￾text of cereals, covers a wide range of processes. In general they are methods of transforming whole grains into forms suitable for consumption or for conversion into consumable products. Milling processes do not themselves involve intentional heating, although in some cases, as in oat processing, a heating phase precedes the milling, and in maize dry milling a drying phase is included. Characteristic (but not essential) features of milling processes are: 1. Separation of the botanical tissues of the grain In milling processes involving both separation and size reduction the two operations may be carried out in two distinct phases, as in sorghum milling, or, to some extent, combined, as in bread- and soft-wheat milling, where the two processes continue throughout the multi-stage operation (although the emphasis changes as the process proceeds). In rice milling, two stages occur but neither seeks to fragment the endo￾sperm. The first stage removes the husk and the second removes the bran. Even the above distinctions are not absolute as processes are in use for decorticating wheat grains before reduction of size and some rice is milled into flour. It is clear that few generalizations can be made about cereals milling, most milling technologies depend upon a series of individual Processes through which stocks Pass in sequence- (e.g. endosperm from pericarp, testa and 2. Reduction of the endosperm into flour or grits. embryo). Some milling systems include both operations (e.g. white flour milling from wheat), while others involve only one (e.g. rice milling comprises only separation, and wholemeal wheat milling seeks only to reduce particle size). 2. Separate fractions produced by (1)-type Milling schemes are conveniently classified as wet or dry, but this indicates a difference in 3. Change the temperature and/or water content degree rather than an absolute distinction as water is used in almost all separations. Damping or ‘tempering’ features even in ‘dry’ milling; it is considered in detail in Ch. 5 as it is a pre-milling treatment. This chapter is concerned with so￾called dry milling; wet milling processes are dealt with in Ch. 12. Emphasis is placed on preparation for human consumption but the term ‘milling’ also applies to production of animal feeds. A brief description of feed-milling is given in Ch. 15. Mi I I i ng processes The processes are of three types, they may: 1. Change the shape and size of the feedstock. treatments. of the stocks. The processes are described below. Treatments that change shape and size Abrasion Effects depend upon severity, thus: 1. Surface abrasion is a relatively gentle process which removes all or part of the fruit coats 129