FLOUR QUALITY 175 of new-s-s- bonds which would have the effect the total br content of the bread to about 18 of increasing dough rigidity(cf. Ch. 3) mg/kg. Potassium bromate(KBrO3) h as never Use of potassium bromate is permitted to 75 allowed in many European countries; it was mg/kg in the U.S.A. to 50 mg/kg in Canada ally excluded from the list of permitted Sweden; to 40 mg/kg in the Soviet Union; and ives in the U.K. by the potassium Bromate Eire to about 18 mg/kg. KBrO3 is not allowed in (Prohibition as a Flour Improver) Regulations the Netherlands or Australia. The greatest need for 1990 giving rise to considerable initial difficulties bromate occurs in continuous-mix baking, no-time in the baking industry. The changes in the use doughs, frozen doughs, and overnight sponges of oxidizing improvers, consequent upon the as used in Cuba and other Latin/American coun deletion of potassium bromate, are considered in tries. The typical level of addition in these types Ch8(. 201). Its use has also been voluntarily of baking approaches the 75 mg/kg maximum. discontinued in Japan and it is now little used in (Ranum, 1992) New Zealand Hazards associated with potassium L-Ascorbic acid (vitamin C), E300, was first bromate include the fact that, as a strong oxidizing used as a bread improver by jorgensen in 1935 gent, it can cause fire or explosions. It is also It is now used for this purpose in the U.K., most toxic and there is strong evidence for its carcino- European countries and elsewhere, particularly enicity. At normal levels of addition however, in mechanical development processes of bread it is not considered to persist at a significant level, making, such as the Chorleywood Breadmaking into the baked product, when used at permitted Process. The volume increase resulting from use of ascorbic acid is generally less than that obtained Potassium bromate remains in use in the U.S. A. with equivalent weight of potassium bromate although an agreement exists between government and it is more costly The improving effect of and users to reduce usage to a minimum. Although ascorbic acid is mediated by enzymes present in permitted in Canada, its use has declined in recent the four. The functional form is the oxidized years in that country(Ranum, 1992). It has been form dehydroascorbic acid(DHA), which is used commercially as a bread improver since highly effective but cannot be used directly as it 1923. The rate of treatment is 10-45 mg/kg on is unstable. Ascorbic acid is oxidized to dha four weight. The substance acts as an oxidizing through catalytic action of ascorbic acid oxidase agent after the flour has been made into a dough; Injection of oxygen during mixing hastens the it increases the elasticity and reduces the extens- oxidation, making ascorbic acid more effectiv ibility of the gluten. Treatment with bromate has( Chamberlain and Collins, 1977). The oxidation flour, and enables large bakeries to use a constant mixing machine contains an oxygen-enhanced fermentation period atmosphere, e. g. a 50/50 mixture of oxygen Potassium bromate is added to flour after being and air, equivalent to a mixture of 60% oxygen suitably diluted with an inert filler such as calcium plus 40% nitrogen( Ch 8). Under these circum carbonate or calcium sulphate Proprietary brands stances, ascorbic acid alone is as effective an of improver contain 6, 10, 25 or 90%of potassium oxidizing agent as is a combination of ascorbic bromate. The 6% brand is added at the rate of acid and potassium bromate used when the dough 0.022%. Higher levels of potassium bromate are is mixed under partial vacuum. An enzyme DHA used in chemical dough development processes reductase is required for oxidation of sulphydryl SH) compounds by DHA Since untreated flour contains 1-8 mg/kg of Ascorbic acid strengthens the gluten; gas reten bromine(Br), the bread made with untreated tion is thus improved and loaf volume augmented four contains 0.7-5. 6 mg/kg of natural Br. Flour Ascorbic acid does not hasten proving. The treatment with 45 mg/kg of bromate leaves a maximum permitted levels(1989)are 50 mg/kg residue of 15 mg/kg of Br in the loaf, increasing in Belgium and Luxembourg, 100 mg/kg in theFLOUR QUALITY 175 of new -S-S- bonds which would have the effect the total Br content of the bread to about 18 of increasing dough rigidity (cf. Ch. 3). mg/kg. Potassium bromate (KBr03) has never been Use of potassium bromate is permitted to 75 allowed in many European countries; it was mg/kg in the U.S.A.; to 50 mg/kg in Canada, specifically excluded from the list of permitted Sweden; to 40 mg/kg in the Soviet Union; and in additives in the U.K. by the Potassium Bromate Eire to about 18 mg/kg. KBr03 is not allowed in (Prohibition as a Flour Improver) Regulations the Netherlands or Australia. The greatest need for 1990 giving rise to considerable initial difficulties bromate occurs in continuous-mix baking, no-time in the baking industry. The changes in the use doughs, frozen doughs, and overnight sponges, of oxidizing improvers, consequent upon the as used in Cuba and other LatdAmerican coun￾deletion of potassium bromate, are considered in tries. The typical level of addition in these types Ch. 8 (p. 201). Its use has also been voluntarily of baking approaches the 75 mg/kg maximum. discontinued in Japan and it is now little used in (Ranum, 1992). New Zealand. Hazards associated with potassium L-Ascorbic acid (vitamin C), E300, was first bromate include the fact that, as a strong oxidizing used as a bread improver by Jgrgensen in 1935. agent, it can cause fire or explosions. It is also It is now used for this purpose in the U.K., most toxic and there is strong evidence for its carcino- European countries and elsewhere, particularly genicity . At normal levels of addition however, in mechanical development processes of bread￾it is not considered to persist at a significant level, making, such as the Chorleywood Breadmaking into the baked product, when used at permitted Process. The volume increase resulting from use levels. of ascorbic acid is generally less than that obtained Potassium bromate remains in use in the U.S.A. with equivalent weight of potassium bromate, although an agreement exists between Government and it is more costly. The improving effect of and users to reduce usage to a minimum. Although ascorbic acid is mediated by enzymes present in permitted in Canada, its use has declined in recent the flour. The functional form is the oxidized years in that country (Ranum, 1992). It has been form dehydroascorbic acid (DHA), which is used commercially as a bread improver since highly effective but cannot be used directly as it 1923. The rate of treatment is 10-45 mg/kg on is unstable. Ascorbic acid is oxidized to DHA flour weight. The substance acts as an oxidizing through catalytic action of ascorbic acid oxidase. agent after the flour has been made into a dough; Injection of oxygen during mixing hastens the it increases the elasticity and reduces the extens- oxidation, making ascorbic acid more effective ibility of the gluten. Treatment with bromate has (Chamberlain and Collins, 1977). The oxidation a similar action to that of ageing or maturing the to DHA is improved if the head space of the flour, and enables large bakeries to use a constant mixing machine contains an oxygen-enhanced fermentation period. atmosphere, e.g. a 5050 mixture of oxygen Potassium bromate is added to flour after being and air, equivalent to a mixture of 60% oxygen suitably diluted with an inert filler such as calcium plus 40% nitrogen (Ch. 8). Under these circum￾carbonate or calcium sulphate. Proprietary brands stances, ascorbic acid alone is as effective an of improver contain 6, 10,25 or 90% of potassium oxidizing agent as is a combination of ascorbic bromate. The 6% brand is added at the rate of acid and potassium bromate used when the dough 0.022%. Higher levels of potassium bromate are is mixed under partial vacuum. An enzyme ‘DHA used in chemical dough development processes reductase’ is required for oxidation of sulphydryl (cf. Ch. 8). (-SH) compounds by DHA. Since untreated flour contains 1-8 mg/kg of Ascorbic acid strengthens the gluten; gas reten￾bromine (Br), the bread made with untreated tion is thus improved and loaf volume augmented. flour contains 0.7-5.6 mg/kg of natural Br. Flour Ascorbic acid does not hasten proving. The treatment with 45 mg/kg of bromate leaves a maximum permitted levels (1989) are 50 mg/kg residue of 15 mg/kg of Br in the loaf, increasing in Belgium and Luxembourg, 100 mg/kg in the