TECHNOLOGY OF CEREALS maize porridge, made from fine maize grits parse maize meal, and flavoured with cheese, is Transition point Water Flour called"polenta Barley meal is used for making a type of porridge in many countries in the Far East, the Middle East, and North Africa(cf p. 13) Wholemeal four made from sorghum or millet m may be cooked with water to make a porridge like food in African countries and in India Porridge made from parched millet grain in the pressure z/or Soviet union is called Kasha IG. 11. 1 Diagram of an extrusion cooker, showing its components and zones.(Reproduced from Guy, 1989, by Ready-to-eat cereals courtesy of the A.A. C.C. While porridge-type cereals have been con- sumed for many years, the development of ready- injected, and the system was a batch process. The to-eat cereals is relatively recent. Ready-to-eat batch cooking process has now been largely cereals owe their origin to the Seventh Day superseded by continuous cooking processes in Adventist Church, whose members, preferring which cooking and extrusion through a die are an entirely vegetable diet, experimented with the both carried out in a single piece of equipment processing of cereals in the mid-nineteenth century. -a cooking extruder or extrusion-cooker(see Fig a granulated product, "Granula, made by J C. 11.1). Extrusion-cooking is a high-temperature Jackson in 1863, may have been the first commer- short-time(hTST) process in which the material cially available ready-to-eat breakfast cereal. a is plasticized at a relatively high temperature similar product, Granola,, was made by J. H. pressure and shear before extrusion through a die Kellogg by grinding biscuits made from wheat- into an atmosphere of ambient temperature and meal, oatmeal and maizemeal. Mass acceptance of pressure(Linko, 1989a) ready-to-eat cereals was achieved in countries such as the U.S.A. by means of efficient advertizing Continuous cooking Doking methods have man advantages over batch methods: for example The stages in the processing of ready-to-eat continuous methods require less floor space and cereals would include the preparation of the cereal less energy in operation; they permit better con by cleaning, and possibly pearling, cutting or trol of processing conditions, leading to improved grinding; the addition of adjuncts such as salt, quality of the products. moreover, batch cooking malt, sweeteners and flavouring materials; mixing methods were usually restricted to the use of with sufficient water to give a paste or dough whole grain or to relatively large grain fragments of the required moisture content; cooking the whereas extrusion cooking can also utilize much mixture; cooling and partially drying, and shaping finer materials, including flor the material by, e.g. rolling, puffing, shredding An extrusion cooker is a continuous processing Batch cooking unit based on a sophisticated screw system rotating within the confines of a barrel. Raw materials are Until recently, rotating vessels246 TECHNOLOGY OF CEREALS maize porridge, made from fine maize grits or called ‘polenta’. Barley meal is used for making a type of porridge in many countries in the Far East, the Middle East, and North Africa (cf. p. 13). Wholemeal flour made from sorghum or millet may be cooked with water to make a porridge- G F E D c B like food in African countries and in India. Porridge made from parched millet grain in the Soviet Union is called Kushu. coarse maize meal, and flavoured with cheese, is Tronsition point Woter Flour I pll?re lzl Conveying zone 1 zOne I Conveying zone Al Mixing zone FIG. 11.1 Diagram of an extrusion cooker, showing its components and zones. (Reproduced from Guy, 1989, by Ready-to-eat cereals courtesy of the A.A.C.C.) While porridge-type cereals have been con￾sumed for many years, the development of ready￾to-eat cereals is relatively recent. Ready-to-eat cereals owe their origin to the Seventh Day Adventist Church, whose members, preferring an entirely vegetable diet, experimented with the processing of cereals in the mid-nineteenth century. A granulated product, ‘Granula’, made by J. C. Jackson in 1863, may have been the first comer￾cially available ready-to-eat breakfast cereal. A similar product, ‘Granola’, was made by J. H. Kellogg by grinding biscuits made from wheat￾meal, oatmeal and maizemeal. Mass acceptance of ready-to-eat cereals was achieved in countries such as the U.S.A. by means of efficient advertizing. Processing The stages in the processing of ready-to-eat cereals would include the preparation of the cereal by cleaning, and possibly pearling , cutting or grinding; the addition of adjuncts such as salt, malt, sweeteners and flavouring materials; mixing with sufficient water to give a paste or dough of the required moisture content; cooking the mixture; cooling and partially drying, and shaping the material by, e.g. rolling, puffing, shredding, into the desired form, followed by toasting, which also dries the material to a safe m.c. for packaging. Batch cooking Until recently, the cooking was carried out in rotating vessels, ‘cookers’, into which steam was injected, and the system was a batch process. The batch cooking process has now been largely superseded by continuous cooking processes in which cooking and extrusion through a die are both carried out in a single piece of equipment - a cooking extruder or extrusion-cooker (see Fig. 11.1). Extrusion-cooking is a high-temperature, short-time (HTST) process in which the material is plasticized at a relatively high temperature, pressure and shear before extrusion through a die into an atmosphere of ambient temperature and pressure (Linko, 1989a). Continuous cooking Continuous cooking methods have many advantages over batch methods: for example, continuous methods require less floor space and less energy in operation; they permit better con￾trol of processing conditions, leading to improved quality of the products. Moreover, batch cooking methods were usually restricted to the use of whole grain or to relatively large grain fragments, whereas extrusion cooking can also utilize much finer materials, including flour. Extrusion cookers An extrusion cooker is a continuous processing unit based on a sophisticated screw system rotating within the confines of a barrel. Raw materials are transported into a cooking zone where they are compressed and sheared at elevated temperatures