BREAKFAST CEREALS AND OTHER PRODUCTS OF EXTRUSION COOKING Sugar-coated products reaction is known to occur, for example, in the ked or puffed cereals, prepared as described. roller-drying of milk, and may be the explanation are sometimes coated with sugar or candy. The of the improved antioxidant activity of oat products process described in BP No. 754, 771 uses a inactivation- stabilization(cf sucrose syrup containing 1-8% of other sugars 165,244) Similarly, enzyme-inactivated, stabilized wheat (e. g. honey)to provide a hard transparent coating bran has a long shelf life: this material can be conditions. The sugar content of corn flakes was used for breakfast cereals, snack foods. extruded products which need a high fibr raised from 7 to 43%by the coating process, extended shelf-life( Cooper, 1988) that of puffed wheat from 2 to 51%. As an The addition of synthetic antioxidants, such as alternative to sugar, use of aspartame as a sweetener bhA or bhT, to the prepared breakfast cereal for breakfast cereals is described in U.s. Pat. N 4, 501, 759 and U.S. Pat. No. 4, 540, 587, while or to the packaging material as an impregnation, the use of a dipeptide sweetener is disclosed as practised in the U.S.A., is not at present in U.S. Pat. Nos. 4, 594, 252, 4, 608, 263 and permitted in the U. K.(cf. p. 178). In Japan 4,614,657 where addition of antioxidants is not permitted use is made of oxygen absorbers to restrict the onset of oxidative rancidity (Juliano, 1985) Keeping quality of breakfast cereals Another form of deterioration of breakfast cereals after processing and packaging is moisture The keeping quality of the prepared product uptake which causes loss of the distinctive crisp depends to a large extent on the content and texture moisture uptake is prevented by the use keeping quality of the oil contained in it. Thus, of the correct type and quality of moisture products made from cereals having a low oil vapour-proof packaging materials(Fast, 1987) content (wheat, barley, rice, maize grits: oil content 1. 5-2.0%)have an advantage in keeping quality over products made from oats(oil content: Oat bran 4-11%, average 7%). Whole maize has high oil a boost has been given to the use of oat bran content(4.4%), but most of the oil is contained in breakfast cereals following the discovery that in the germ which is removed in making grits this material has a hypocholesterolaemic effect in the human( de groot et al., 1963), that is, it causes The keeping quality of the oil depends on its a lowering of the concentration of plasma choles- degree of unsaturation, the presence or absence terol in the blood. As high blood cholesterol has of antioxidants and pro-oxidants, the time and been associated with the incidence of coronary temperature of the heat treatment, the moisture heart disease for each 1% fall in plasma content of the material when treated, and the cholesterol, coronary heart disease falls by 2% conditions of storage (Nestel, 1990)-a dietary factor that will reduce Severe heat treatment, as in toasting or puffing, blood cholesterol is to be welcomed may destroy antioxidants or induce formation of The content of soluble fibre is much higher in pro-oxidants, stability of the oil being progres- oat bran(10.5%)than in wheat bran(2.8%); this sively reduced as treatment temperature is raised, may be an important factor in the cholesterol treatment time lengthened or moisture content lowering activity of oat bran(not shown by wheat of the material at the time of treatment lowered bran), and it has been suggested that a hemi- On the other hand, momentary high-temperature cellulose, beta-D-glucan, which is the major con- treatment, as at the surface of a hot roll in the stituent of the soluble fibre, is the cholesterol- roller-drying of a batter produce new anti- lowering agent, acting by increasing the faecal oxidants by interaction of protein and sugar(non- excretion of cholesterol(Illman and Topping enzymic browning, or Maillard reaction); such a 1985; Oakenfull, 1988; Seibert, 1987)BREAKFAST CEREALS AND OTHER PRODUCTS OF EXTRUSION COOKING 251 reaction is known to occur, for example, in the roller-drying of milk, and may be the explanation made from oats after steam treatment for lipase Similarly, enzyme-inactivated, stabilized wheat bran has a long shelf life: this material can be used for breakfast cereals, snack foods, extruded products which need a high fibre content and extended shelf-life (Cooper, 1988). The addition of synthetic antioxidants, such as BHA or BHT, to the prepared breakfast cereal, or to the packaging material as an impregnation, permitted in the U.K. (cf. p. 178). In Japan, where addition of antioxidants is not permitted, use is made of oxygen absorbers to restrict the onset of oxidative rancidity (Juliano, 1985). Another form of deterioration of breakfast cereals after processing and packaging is moisture uptake which causes loss of the distinctive crisp texture. Moisture uptake is prevented by the use of the correct type and quality of moisture vapour-proof packaging materials (Fast, 1987). Oat bran A boost has been given to the use of oat bran in breakfast cereals following the discovery that this material has a hypocholesterolaemic effect in the human (de Groot et al., 1963), that is, it causes a lowering of the concentration of plasma choles￾terol in the blood. As high blood cholesterol has been associated with the incidence of coronary heart disease - for each 1% fall in plasma cholesterol, coronary heart disease falls by 2% (Nestel, 1990) - a dietary factor that will reduce blood cholesterol is to be welcomed. The content of soluble fibre is much higher in oat bran (10.5%) than in wheat bran (2.8%); this may be an important factor in the cholesterol￾lowering activity of oat bran (not shown by wheat bran), and it has been suggested that a hemi￾cellulose , beta-D-glucan, which is the major con￾stituent of the soluble fibre, is the cholesterol￾lowering agent, acting by increasing the faecal excretion of cholesterol (Illman and Topping, 1985; Oakenfull, 1988; Seibert, 1987). Sugar-coated products are sometimes coated with sugar or candy. The sucrose syrup containing 1-8% of other sugars (e.g. honey) to provide a hard transparent coating that does not become sticky even under humid conditions. The sugar content of corn flakes was raised from 7 to 43% by the coating process, that of puffed wheat from 2 to 51%. As an alternative to sugar, use of aspartame as a sweetener for breakfast cereals is described in U.S. Pat. No. the use of a dipeptide sweetener is disclosed in '.'e Pat* Nos* 4y594y252y 4y608y263 and 4,614,657. F1aked Or puffed ceredsY prepared as described, of he improved antioxidant activity of oat products process described in BP No* 754y771 uSeS a inactivation - stabilization (cf. pp. 165, 244). 4,501Y759 and u*s. Pat. No' 4,540,587, whi1e as practised in the U.S.A., is not at present Keeping quality of breakfast cereals The keeping quality of the prepared product depends to a large extent on the content and keeping quality of the oil contained in it. Thus, products made from cereals having a low oil content (wheat, barley, rice, maize grits: oil content 1.5-2.0%) have an advantage in keeping quality over products made from oats (oil content: 4-11%, average 7%). Whole maize has high oil content (4.4%), but most of the oil is contained in the germ which is removed in making grits (cf. p. 138). The keeping quality of the oil depends on its degree of unsaturation, the presence or absence of antioxidants and pro-oxidants, the time and temperature of the heat treatment, the moisture content of the material when treated, and the conditions of storage. Severe heat treatment, as in toasting or puffing, may destroy antioxidants or induce formation of pro-oxidants, stability of the oil being progres￾sively reduced as treatment temperature is raised, treatment time lengthened, or moisture content of the material at the time of treatment lowered. On the other hand, momentary high-temperature treatment, as at the surface of a hot roll in the roller-drying of a batter, may produce new anti￾oxidants by interaction of protein and sugar (non￾enzymic browning, or Maillard reaction); such a