BREAKFAST CEREALS AND OTHER PRODUCTS OF EXTRUSION COOKING Puffed products with the enrichment, and bumped more heavily than for Krispies, then oven-puffed and toasted Cereals may be puffed in either of two ways: The high protein enrichment may be vital wheat by sudden application of heat at atmospheric gluten, defatted wheat germ, non-fat dry milk pressure so that the water in the cereal is vapor- or dried yeast, plus vitamins, minerals and anti ized in situ, thereby expanding the product(oven buffing); or by the sudden transference of the oxidants ( uliano and Sakurai, 1985) cereal containing superheated steam from a high pressure to a low pressure, thereby allowing the Gun-puffed rice water suddenly to vaporize and cause expansion Long-grain white rice or parboiled medium gun puffing). The key to the degree of puffing grain rice, Is generally used for gun-puffing of the cooked grain is the suddenness of change although short-grain, low-amylose (waxy )rice in temperature or pressure(Hoseney, 1986) is used for gun-puffing in the U.S.A. and par- wheat,oats or pearl barley, which are prepared boiled waxy rice may be used in the Philippines by cleaning, conditioning and depericarping(e.g. colour and tends to undergo oxidative rancid by a wet scouring proces etc.) are added as for faster than puffed raw rice, but parboiled rice faked products requires less treatment, viz. lower steam pressure and temperature, than raw rice uliano and Sak 1985) Oven-puffed rice a batch of the prepared grain is preheated to 5210-638C and fed to the puffing gun, a pressure Oven-puffed rice is made from raw or parboiled chamber with an internal volume of 0.5-1.0 ft' milled rice which is cooked, with the adjuncts, which is heated externally and by injection of for 1 h at 15-18 lb/inin a rotary cooker until superheated steam, so that the internal pressure uniformly translucent. It is dried to 30% m.c. rapidly builds up to about 200 lb/in(1 379 MN/ tempered for 24 h, dried again, this time to 20% m")at temperatures up to 242C, and the starch m.c., and subjected to radiant heat to plasticize in the material becomes gelatinized The pressure the outside of the grain. The grain is ' bumped' is suddenly released by opening the chamber of through smooth rolls, just sufficiently to fatten the puffing gun. The material is shot'out, and compress it, and then surface dried to about expansion of water vapour on release of the 15%mc, and tempered again for 12-15 h at pressure blowing up the grains or pellets to room temp The bumped rice then passes to the several times their original size. The puffed toasting oven, where it remains for 30-90 sec. product is dried to 3%mc. by toasting, then The temperature in the oven is about 300C in cooled and packaged (Fast, 1987; Fast and the latter half of the oven-cycle - as hot as Caldwell, 1990; Juliano and Sakurai, 1985) ossible short of scorching the grains. due to the For satisfactory puffing, the starch should have bumping, which has compressed the grains, and plastic flow characteristics under pressure, and the high temperature, the grains immediately hence the temperature should be high enoug puff to 5-6 times their original size. The puffed Moreover, the material at the moment before grains are cooled, fortified with vitamins and expansion requires cohesion to prevent shattering minerals, if required, and treated with anti- and elasticity to permit expansion. The balance oxidants(Hoseney, 1986; Juliano and Sakurai, between these two characteristics can be varied 1985). Kellog's Rice Krispies'is a well-known by adding starch, which has cohesive properties. brand of oven-puffed rice Kellogg's "Special K, Extruded gun-puffed cereals can be made from ontaining 20% of protein, is made in a similar oat flour or maize meal, with which tapioca or way to Rice Krispies up to the drying before rye four can be blended. This material is fed pumping The material is then wetted, coated into the cooking extruder and a solution of theBREAKFAST CEREALS AND OTHER PRODUCTS OF EXTRUSION COOKING 249 with the enrichment, and bumped more heavily than for Krispies, then oven-puffed and toasted. gluten, defatted wheat germ, non-fat dry milk, or dried yeast, plus vitamins, minerals and anti￾oxidants (Juliana and Sakurai, 1985). Gun-puffed rice Puffed products by sudden application of heat at atmospheric pressure so that the water in the cereal is vapor￾ized in situ, thereby expanding the product (oven puffing); or by the sudden transference of the cereal containing superheated steam from a high pressure to a low pressure, thereby allowing the water suddenly to vaporize and cause expansion Cerea1s may be puffed in either Of tWo ways: The high protein enrichment may be vital wheat Long-grain white rice or parboiled medium- (gun puffing)* The key to the degree Of puffing Of the cooked grain is the suddenness Of change grain rice is generally used for gun-puffing, although short-grain, low-amylose (Gwaxy7) rice is used for gun-puffing in the U.S.A., and par￾Puffed parboiled rice has a darker, less acceptable colour and tends to undergo oxidative rancidity faster than puffed raw rice, but parboiled rice requires less treatment, viz. lower steam pressure and temperature, than raw rice (Juliano and Sakurai, 1985). A batch of the prepared grain is preheated to 521”-638”C and fed to the puffing gun, a pressure 0 ven -p u ffed rice Oven-puffed rice is made from raw or parboiled chamber with an internal volume of 0.5-1 .O ft3, milled rice which is cooked, with the adjuncts, which is heated externally and by injection of for 1 h at 15-18 lblin2 in a rotary cooker until superheated steam, so that the internal pressure uniformly translucent. It is dried to 30% m.c., rapidly builds up to about 200 lb/in2 (1.379 MN1 tempered for 24 h, dried again, this time to 20% m2) at temperatures up to 242”C, and the starch m.c., and subjected to radiant heat to plasticize in the material becomes gelatinized. The pressure the outside of the grain. The grain is ‘bumped’ is suddenly released by opening the chamber of through smooth rolls, just sufficiently to flatten the puffing gun. The material is ‘shot’ out, and compress it, and then surface dried to about expansion of water vapour on release of the 15% m.c., and tempered again for 12-15 h at pressure blowing up the grains or pellets to room temp. The bumped rice then passes to the several times their original size. The puffed toasting oven, where it remains for 30-90 sec. product is dried to 3% m.c. by toasting, then The temperature in the oven is about 300°C in cooled and packaged (Fast, 1987; Fast and the latter half of the oven-cycle - as hot as Caldwell, 1990; Juliano and Sakurai, 1985). possible short of scorching the grains. Due to the For satisfactory puffing, the starch should have bumping, which has compressed the grains, and plastic flow characteristics under pressure, and the high temperature, the grains immediately hence the temperature should be high enough. puff to 5-6 times their original size. The puffed Moreover, the material at the moment before grains are cooled, fortified with vitamins and expansion requires cohesion to prevent shattering minerals, if required, and treated with anti- and elasticity to permit expansion. The balance oxidants (Hoseney, 1986; Juliano and Sakurai, between these two characteristics can be varied 1985). Kellog’s ‘Rice Krispies’ is a well-known by adding starch, which has cohesive properties. brand of oven-puffed rice. Kellogg’s ‘Special K’ , Extruded gun-puffed cereals can be made from containing 20% of protein, is made in a similar oat flour or maize meal, with which tapioca or way to Rice Krispies up to the drying before rye flour can be blended. This material is fed bumping. The material is then wetted, coated into the cooking extruder and a solution of the in temperature or pressure (Hoseney, 1986). wheat, oats or pearl barley, which are prepared by cleaning, conditioning and depericarping (e.g. by a wet scouring process). Flavouring adjuncts (sugar, malt syrup, salt, etc.) are added as for flaked products. The preferred grains for puffing are riceY boiled waxy rice may be used in the Philippines