counter-current of air at about 65C under con- slightly narrower than the width of the grain trolled humidity conditions, to ensure uniform Without fragmenting the grain, bumping disrupts drying, to a moisture content of about 20%o, a the bran coat, assisting the penetration of wate process taking 2.5-3 h, and are then cooled and Flavouring adjuncts-sugar, malt syrup, salt rested to allow equilibration of moisture. The are then added and the grain is pressure cooked resting period was formerly about 24 h, but at about 15 psi for 30-35 min. The cooked wheat, is considerably less under controlled humidity at 28-30%m c, emerges in big lumps which have drying conditions. The dried grits are then faked to be'delumped, and then dried from about 30% on counter-rotating rollers, which have a surface m.c. to 16-18%mc. After cooling to about 43.C, temperature of 4346C, at a pressure of 40 t at the grain is binned to temper for a short time the point of contact, and the flakes thus formed and faked (as for maize). Just before faking, the are toasted in tunnel or travelling ovens at 300c grain is heated to about 88c to plasticize the for about 50 sec. The desirable blistering of the kernels and prevent tearing on the faking rolls surface of the flakes is related to the roller The fakes leave the rolls at about 15-18%mc surface temperature and to the moisture content and are then toasted and dried to 3% m of the grits, which should be 10-14% m c. when rolled. After cooling, the fakes may be sprayed with solutions of vitamins and minerals before Rice flakes packaging To make rice flakes using the traditional pr the preferred starting material is head rice(whole Extruded升akes de-husked grains) or 2nd heads (large broken kernels). Flavouring adjuncts are similar to those These, made from maize or wheat, are cooked used with maize and wheat. The blend of rice in an extrusion cooker, rather than in a batch plus adjuncts is pressure-cooked at 15-18 psi for pressure cooker, and can be made from fine meal about 60 min. The moisture content of the cooked or flour rather than from coarse grits. The dry material should not exceed 28% m.c., otherwise material is fed continuously into the extrusion it becomes sticky and difficult to handle. De cooker,and is joined by a liquid solution of the lumping, drying (to about 17% m.c. at lower flavouring materials- sugar, malt, salt, etc. moisture contents the particles shear; at higher These are mixed together by the rotation of the moisture contents the flaking rolls become screw and conveyed through the heated barrel, gummed up), cooling, tempering(up to 8 h)and thereby becoming cooked faking are as for wheat flakes The material is extruded through the die in the In the toasting of the rice fakes, more heat is form of ribbons which are cut to pellet size by a required than for making wheat flakes. The rotating knife The pellets are then dried, tem- moisture content of the feed and the heat of the pered, faked and toasted as described for the oven are adjusted so that the fakes blister and traditional method (Fast, 1987; Fast and Caldwell, puff during toasting; accordingly, the discharge 1990; Hoseney, 1986; Midden, 1989; Rooney and end of the oven is hotter than the feed end Serna-Saldivar, 1987 The moisture content of the final product is 1-3% Flaked products from wheat and rice o The process for making rice flakes by extrusion sembles that described for maize and wheat, Wheat flakes except that a colouring material is added to offset the dull or grey appearance caused by mechanical These are traditionally made from whole wheat working during extrusion. The lack of natural grain, which is conditioned with water to about colour is emphasized if the formulation is low in 21%mc and then'bumped by passing through sugar or malt syrup as sources of reducing sugars a pair of smooth rollers set so that the roll gap is that could participate in a maillard reaction248 TECHNOLOGY OF CEREALS counter-current of air at about 65°C under con- slightly narrower than the width of the grain. trolled humidity conditions, to ensure uniform Without fragmenting the grain, bumping disrupts drying, to a moisture content of about 20%, a the bran coat, assisting the penetration of water. process taking 2.5-3 h, and are then cooled and Flavouring adjuncts - sugar, malt syrup, salt - rested to allow equilibration of moisture. The are then added and the grain is pressure cooked resting period was formerly about 24 h, but at about 15 psi for 30-35 min. The cooked wheat, is considerably less under controlled humidity at 28-30% m.c., emerges in big lumps which have drying conditions. The dried grits are then flaked to be ‘delumped’, and then dried from about 30% on counter-rotating rollers, which have a surface m.c. to 16-18% m.c. After cooling to about 43”C, temperature of 43”-46”C, at a pressure of 40 t at the grain is binned to temper for a short time, the point of contact, and the flakes thus formed and flaked (as for maize). Just before flaking, the are toasted in tunnel or travelling ovens at 300°C grain is heated to about 88°C to plasticize the for about 50 sec. The desirable blistering of the kernels and prevent tearing on the flaking rolls. surface of the flakes is related to the roller The flakes leave the rolls at about 15-18% m.c. surface temperature and to the moisture content and are then toasted and dried to 3% m.c. of the grits, which should be 10-14% m.c. when Rice flakes rolled. After cooling, the flakes may be sprayed with solutions of vitamins and minerals before packaging. To make rice flakes using the traditional process, the preferred starting material is head rice (whole de-husked grains) or 2nd heads (large broken kernels). Flavouring adjuncts are similar to those Extruded flakes These, made from maize or wheat, are cooked used with maize and wheat. The blend of rice in an extrusion cooker, rather than in a batch plus adjuncts is pressure-cooked at 15-18 psi for pressure cooker, and can be made from fine meal about 60 min. The moisture content of the cooked or flour rather than from coarse grits. The dry material should not exceed 28% m.c., otherwise material is fed continuously into the extrusion it becomes sticky and difficult to handle. De￾cooker, and is joined by a liquid solution of the lumping, drying (to about 17% m.c.: at lower flavouring materials - sugar, malt, salt, etc. moisture contents the particles shear; at higher These are mixed together by the rotation of the moisture contents the flaking rolls become screw and conveyed through the heated barrel, gummed up), cooling, tempering (up to 8 h) and thereby becoming cooked. flaking are as for wheat flakes. The material is extruded through the die in the In the toasting of the rice flakes, more heat is form of ribbons which are cut to pellet size by a required than for making wheat flakes. The rotating knife. The pellets are then dried, tem- moisture content of the feed and the heat of the pered, flaked and toasted as described for the oven are adjusted so that the flakes blister and traditional method (Fast, 1987; Fast and Caldwell, puff during toasting; accordingly, the discharge 1990; Hoseney, 1986; Midden, 1989; Rooney and end of the oven is hotter than the feed end. Serna-Saldivar, 1987). The moisture content of the final product is 1-3% m.c. The process for making rice flakes by extrusion resembles that described for maize and wheat, Flaked products from wheat and rice except that a colouring material is added to offset the dull or grey appearance caused by mechanical Wheat flakes These are traditionally made from whole wheat working during extrusion. The lack of natural grain, which is conditioned with water to about colour is emphasized if the formulation is low in 21% m.c. and then ‘bumped’ by passing through sugar or malt syrup as sources of reducing sugars a pair of smooth rollers set so that the roll gap is that could participate in a Maillard reaction