Flour Quality Introduction Table 7. 1 shows typical proportions of flour streams e: In the milling of cereals by the gradual reduc. (expressed as percentages of the wheat)from well-equipped and well-adjusted mill in the U. K on system(see Ch 6), flour is produced by every making flours of fairly low ash yield. The ash machine in the break scratch and reduction systems of the normal mill-flow. The stock fed yield of the individual flour streams is also shown Flour streams with the lowest ash yield (e. g in terms of proportions of endosperm, embryo group l in Table 7. 1)may be described as'patent and bran contained in it, and the region of the four. Those from the end of the milling process grain from which the endosperm is derived with high ash yield are called 'low-grade' in the and each machine flour is correspondingly distinc- TABLE 7.1 tive in respect of baking quality, colour and Typical Proportions and Ash Yields of Flour Streams granularity, contents of fibre and nutrients, and the amount of ash it yields upon incineration Proportions Ash yield ( of feed(%, d.m.) By far the most abundant four consumed in Flour streams to I Bk the industrialized world is derived from wheat because of this, and the unique versatility ofGroup 1:High Grade 12.0-21.00.350.38 wheaten flour, the majority of this chapter is devoted to it. flours from other cereals are ABC 14.0-17 70-100.380.47 35400.350 given some In the U.K. today there are no recognized Group 2: Middle Grade 2.5-7.50.390.70 standards for flour grades: each miller makes his E grades according to customers requirements, and 1.3-3.00.75-1,47 exercises his skill in maintaining regularity of 1.5-2.50.500.72 II Bk 1.5-3.00.53-0 quality for any particular grade iiI Bk bran finisher four 0.02.50.70-1,00 0.00.70.700.90 I Bk Coarse Midds 3.06.00.500.82 Flour grades II Bk Coarse Midd 1.5-3.50.700 25-300.700.80 If the flour streams from all the machines in Group 3: Low grade the break, scratch and reduction systems are B2 blended together in their rational proportions,F 1.2-2.50.40-0.45 0.7-1.20.58-1.3 the resulting four is known as ' straight-run H 0.61.2 grade. Other grades are produced by selecting 0.5-0.70.882.25 and blending particular four streams, frequently IV Bk finisher flour 0.0-1.01.50-2.0 on the basis of their ash yield or grade colour Total group 3 80-2. measures of their non-endosperm tissue content)
7 Flour Quality Introduction Table 7.1 shows typical proportions of flour streams (expressed as percentages of the wheat) from a well-equipped and well-adjusted mill in the U.K. yield of the individual flour streams is also shown. Flour streams with the lowest ash yield (e.g. group 1 in Table 7.1) may be described as ‘patent’ flour. Those from the end of the milling process In the milling of cereals by the gradual reducmachine in the break, scratch and reduction systems of the normal mill-flow. The stock fed to each grinding stage is distinctive in composition - in terms of proportions of endosperm, embryo grain from which the endosperm is derived - and each machine flour is correspondingly distinctive in respect of baking quality, colour and granularity, contents of fibre and nutrients, and the amount of ash it yields upon incineration. By far the most abundant flour consumed in the industrialized world is derived from wheat; because of this, and the unique versatility of wheaten flour, the majority of this chapter is ti’n system (see Ch’ 6), flour is produced by every making flours of fairly low ash yield. The ash and bran contained in it, and the region of the with high ash yield are called ~l~~-~~~d~’ in the TABLE 7.1 Typical Proportions and Ash Yields of Flour Streams Proportions Ash yield (% of feed (%, d.m.) Flour streams Group 1: High Grade to I Bk) A 12 .O-2 1.0 0.35-0.38 B 14.0-17.0 0.35-0.38 C 7.0-10 0.38-0.47 3540 0.35-0.40 devoted to it. Flours from other cereals are however given some consideration. In the U.K. today there are no recognized Total group 1 Group 2: Middle Grade D 2.5-7.5 0.39-0.70 standards for flour grades: each miller makes his E 1.7-2.1 0.45-0.89 grades according to customer’s requirements, and G 1.3-3.0 0.75-1.47 I Bk 1.5-2.5 0.50-0.72 II Bk quality for any particular grade. I11 Bk 0.0-1.5 0.70-1.00 I11 Bk bran finisher flour 0.0-2.5 0.70-1.00 X (Scratch) 0.0-0.7 0.70-0.90 I Bk Coarse Midds 3.0-6.0 0.50-0.82 Flour grades I1 Bk Coarse Midds 1.5-3.5 0.70-0.84 1.5-3.0 0.53-0.69 exercises his skill in maintaining regularity of Total Group 2 25-30 0.70-0.80 If the flour streams from all the machines in Group 3: Low grade the break, scratch and reduction systems are B2 1.2-2.5 0.40-0.45 the resulting flour is known as ‘straight-run H 0.6-1.2 0.60-1.53 0.5-0.7 0.88-2.25 2.04.0 1.00-2.00 and blending particular flour streams, frequently IV Bk finisher flour 0.0-1.0 1.50-2.00 0.0-1.0 1.00-2.50 8-10 1.80-2.3 blended together in their rational proportions, F 0.7-1.2 0.58-1.35 J Iv Bk v Bk grade’. Other grades are produced by selecting on the basis of their ash yield or grade colour (measures of their non-endosperm tissue content). Total Group 3 170
FLOUR QUALITY 171 U. K. or 'clear'flour in the U.S.A. Clear four is replaced chlorine in 1922 as an improving and used industrially in the U. S A for the manufac- bleaching agent for breadmaking four because ture of alcohol, gluten, starch and adhesives(see was much more effective. Its use was discontinued Ch.15) in the u.s.a. in 1949 and in the u.k. from the end of 1955, after it had been shown by Mellanby Treatments of wheat flour (1946) that flour treated with Agene in large doses ht cause le hysteria (although Agene- treated four has never been shown to be harmful ng to human health). Nitrogen trichloride reacts Flour contains a yellowish pigment, of which with the amino acid methionine, present in wheat about 95% consists of xanthophyll or its esters, protein, to form a toxic derivative, methionine and has no nutritional significance. Bleaching of sulphoximine( bentley et al., 1950). the natural pigment of wheat endosperm by oxidation occurs rapidly when flour is exposed the atmosphere, more slowly when flour is stored Chlorine dioxide in bulk and by chemical Chlorine dioxide(CIO2), known as 'Dyox',is treatment. The principal agents used, or formerly now the most widely used improving and bleaching used, for bleaching four are nitrogen peroxide, agent in the U. K, the u.s.A. Australia and chlori hlorine dioxide, nitrogen trichloride, Canada. It was first used for these purposes in nzoyl peroxide and acetone peroxide 1949 in the U.s.A. and in the u. K. in 1955. The gas is produced by passing chlorine gas through Nitrogen peroxide (NO2) an aqueous solution of sodium chlorite. Dyox gas contains a maximum of 4%CIO. The chlorine NO2 produced by a chemical reaction or by dioxide gas is released by passing air through the the electric arc process was widely used as a solution, and is applied to breadmaking flour at bleaching agent in the early twentieth century. a rate of 12-24 mg/kg (it is permitted in the U. K Its use has been discontinued except in the u.s.a up to 30 mg/kg). Chlorine dioxide treatment of and Australia, where it is still legally permitted. flour destroys the tocopherols(cf Ch. 14). The use of chlorine dioxide is also permitted in Japan Chlorine The use of chlorine gas(Cl2) for treatment of Benzoyl peroxide cake four(except wholemeal) is permitted in the (C6 CO)2O2 or BzO2 is a solid bleaching U.K. to a maximum of 2500 mg/kg. The chlorine agent which was first used in 1921. It is supplied modifies the properties of the starch for high- as a mixture with inert, inorganic fillers such as ratio cake flour (cf p. 178). For cake flours the CaHPO4, Ca3(PO4)2, sodium aluminium sulphate usual level of treatment is 1000-1800 mg/kg. The or chalk Novadelox, a proprietary mixture, con Bread and Flour Regulations 1984 do not permit tains up to 32% of benzoyl peroxide but 16% is its use in bread flour in the U. K. The use of the usual proportion. The dosage rate, normally chlorine is not permitted in most European 45-50 mg/kg, is restricted to 50 mg/kg in the countries, but it is allowed in four for all purposes U. K. by the Bread and Flour regulations 1984 in the u.s.A., Canada, Australia, New Zealand The bleaching action occurs within about 48 h (to 1500 mg/kg)and South Africa(to 2500mg/kg) his bleacher has the advantage over gaseous agents that only a simple feeder is required, and Nitrogen trichloride storage of chemicals presents no hazard; the fact that it has no improving action is advantageous This gas(NCl3), known as 'Agene,, was patented in the bleaching of patent fours. The treated flour s a four bleach by j. C. Baker in 1921, and contains traces of benzoic acid but objection has
FLOUR QUALITY 171 replaced chlorine in 1922 as an improving and bleaching agent for breadmaking flour because it was much more effective. Its use was discontinued in the U.S.A. in 1949 and in the U.K. from the end of 1955, after it had been shown by Mellanby (1946) that flour treated with Agene in large doses might cause canine hysteria (although Agenetreated flour has never been shown to be harmful to human health). Nitrogen trichloride reacts with the amino acid methionine, present in wheat protein, to form a toxic derivative, methionine sulphoximine (Bentley et al., 1950). Chlorine dioxide Chlorine dioxide (C102), known as ‘Dyox’, is now the most widely used improving and bleaching agent in the U.K., the U.S.A., Australia and Canada. It was first used for these purposes in 1949 in the U.S.A. and in the U.K. in 1955. The gas is produced by passing chlorine gas through an aqueous solution of sodium chlorite. Dyox gas contains a maximum of 4% C102. The chlorine dioxide gas is released by passing air through the solution, and is applied to breadmaking flour at a rate of 12-24 mg/kg (it is permitted in the U.K. up to 30 mg/kg). Chlorine dioxide treatment of flour destroys the tocopherols (cf. Ch. 14). The use of chlorine dioxide is also permitted in Japan. Benzoyl peroxide (C6H5C0)202 or Bz02 is a solid bleaching agent which was first used in 1921. It is supplied as a mixture with inert, inorganic fillers such as CaHP04, Ca3(P04)2, sodium aluminium sulphate or chalk. Novadelox, a proprietary mixture, contains up to 32% of benzoyl peroxide but 16% is the usual proportion. The dosage rate, normally 45-50 mg/kg, is restricted to 50 mg/kg in the U.K. by the Bread and Flour Regulations 1984. The bleaching action occurs within about 48 h. This bleacher has the advantage over gaseous agents that only a simple feeder is required, and storage of chemicals presents no hazard; the fact that it has no improving action is advantageous in the bleaching of patent flours. The treated flour contains traces of benzoic acid, but objection has U.K. or ‘clear’ flour in the U.S.A. Clear flour is used industrially in the U.S.A. for the manufacture of alcohol, gluten, starch and adhesives (see Ch. 15). Treatments of wheat flour Bleaching Flour contains a yellowish pigment, of which about 95% consists of xanthophyll or its esters, and has no nutritional significance. Bleaching of the natural pigment of wheat endosperm by oxidation occurs rapidly when flour is exposed to the atmosphere, more slowly when flour is stored in bulk, and can be accelerated by chemical treatment. The principal agents used, or formerly used, for bleaching flour are nitrogen peroxide, chlorine, chlorine dioxide, nitrogen trichloride, benzoyl peroxide and acetone peroxide. Nitrogen peroxide (NO,) NO2 produced by a chemical reaction or by the electric arc process was widely used as a bleaching agent in the early twentieth century. Its use has been discontinued except in the U.S.A and Australia, where it is still legally permitted. Chlorine The use of chlorine gas (C12) for treatment of cake flour (except wholemeal) is permitted in the U.K. to a maximum of 2500 mg/kg. The chlorine modifies the properties of the starch for highratio cake flour (cf p. 178). For cake flours the usual level of treatment is 1000-1800 mg/kg. The Bread and Flour Regulations 1984 do not permit its use in bread flour in the U.K. The use of chlorine is not permitted in most European countries, but it is allowed in flour for all purposes in the U.S.A., Canada, Australia, New Zealand (to 1500 mg/kg) and South Africa (to 2500mg/kg). Nitrogen trichloride This gas (NC13), known as ‘Agene’, was patented as a flour bleach by J. C. Baker in 1921, and
172 TECHNOLOGY OF CEREALS not been raised BzO2 is also used in New South flours(those nearer the tail end of the break and Wales, Queensland, the U.SA, Canada, the reduction systems) in general requiring more Netherlands, New Zealand (up to 40 mg/kg, for treatment than the patent flours(cf. p. 170). It pastry four only) and Japan(up to 300 mg/kg). is therefore customary to group the machine fours according to quality into three or four Acetone peroxide streams for treatment. a possible grouping is indicated in Table 7. I Each group would be given Acetone peroxide is a dry powder bleaching appropriate bleacher treatment: e. g. the lowest nd improving agent, marketed as'Keetox',a 20% of flour might receive treatment at ten times blend of acetone peroxides with a diluent such as the rate for the best quality 50%. The final grades dicalcium phosphate or starch. The concentration are then made up by blending two or more of the in terms of H2o2 equivalent per 100 g of additive groups in desirable proportions. plus carrier is 3-10 for maturing and bleaching or0.75 for use in doughmaking. Its use has been Flours for various purposes permitted in the U.S.A. since 1961, and also in Canada, but it is not, as yet, permitted in the Wheat flour is used for making foc U. K. It is used either alone or in combination of widely varying moisture content(see Table 7.3) with benzoyl peroxide. The usual dosage rate is 446 mg/kg on flour basis. Significant dates in TABLE 7. 3 Flour-based products and their me history of flour bleaching are summarized Table 7. 2 Moisture content Type of product Range Mean Moisture level Flour blending for bleaching treatment Because the various flour streams differ in their Puddings 1367 Medium characteristics, the optimum level of bleaching 35-40 Mediurn 、 treatment varies correspondingly, the lower grade Pastry Biscuits(cookies, crackers) 1-6 TABLE 7.2 Significant Dates in the History of Flour bleaching Data extracted from McCance and Widdowson(1967) 1901 Andrews patents flour treatment with NO,(chemical The proportions in which the various ingredients of baked products are present in the recipe 1903 Alsop patents flour treatment with NOz(electrical relative to flour(100 parts), are shown in Table 909 NO, in us 7. 4. Biscuit dough is stiff to permit rolling and 1911 Keswick Convention- unmarked flour to be flattening; bread dough is a plastic mass that can 1921 Benzoyl per be moulded and shaped wafer batter is a liquid Ispension that will flow through a pipe 1922 NCl, replaces Cl as bleacher for breadmaking flour 1923 Committee appointed to inquire into use of For comparison with products listed in Tal reservatives and colouring matter in 7. 4, a typical wholemeal wheat extruded snack 1924 Committee's activities extended to chemi formulation would contain the following amounts 1927 Committee reported that bleaching of ingredients, in relation to 100 g white four: 7 g agents were in use, and that Cl, N soya protein, 14 g wheat bran, 1.4 g oil, 0.4 emulsifier, 23 g water, 7 g sugar, 2 g salt, 2 g 1949 C1O, first used in the U. S. A dicalcium phosphate, 3.6 g milk powder(Guy U 993). the U.K 1961 Acetone peroxide permitted in the U.S.A(not in the products, as purchased or as consumed, is shown in Table 7.5
172 TECHNOLOGY OF CEREALS not been raised. Bz02 is also used in New South flours (those nearer the tail end of the break and Wales, Queensland, the U. S.A, Canada, the reduction systems) in general requiring more Netherlands, New Zealand (up to 40 mg/kg, for treatment than the patent flours (cf. p. 170). It pastry flour only) and Japan (up to 300 mg/kg). is therefore customary to group the machine flours according to quality into three or four streams for treatment. A possible grouping is indicated in Table 7.1 Each group would be given Acetone peroxide Acetone peroxide is a dry powder bleaching appropriate bleacher treatment: e.g. the lowest and improving agent, marketed as ‘Keetox’, a 20% of flour might receive treatment at ten times blend of acetone peroxides with a diluent such as the rate for the best quality 50%. The final grades dicalcium phosphate or starch. The concentration are then made up by blending two or more of the in terms of H202 equivalent per 100 g of additive groups in desirable proportions. plus carrier is 3-10 for maturing and bleaching, or 0.75 for use in doughmaking. Its use has been permitted in the U.S.A. since 1961, and also in Canada, but it is not, as yet, permitted in the with benzoyl peroxide. The usual dosage rate is 446 mg/kg on flour basis. Significant dates in the history of flour bleaching are summarized in Table 7.2. Moisture content Flours for various purposes Wheat flour is used for making food products U.K. It is used either alone or in combination of widely varying moisture content (see Table 7.3). TABLE 7.3 Flour-based Products and their Moisture Contents Type of product Range Mean Moisture (Yo) (”/.I level Flour blending for bleaching treatment soup 78-80 85 High 13-67 45 Medium 3540 38 Medium characteristics, the optimum level of bleaching Cakes 5-30 17 Medium Because the various flour streams differ in their Puddings Bread treatment varies correspondingly, the lower grade Pastry 7 Low Biscuits (cookies, crackers) 1-6 5 Low Data extracted from McCance and Widdowson (1967). The proportions in which the various ingredients of baked products are present in the recipe, relative to flour (100 parts), are shown in Table 7.4. Biscuit dough is stiff to permit rolling and flattening; bread dough is a plastic mass that can be moulded and shaped; wafer batter is a liquid suspension that will flow through a pipe. For comparison with products listed in Table 7.4, a typical wholemeal wheat extruded snack formulation would contain the following amounts of ingredients, in relation to 100 g white flour: 7 g soya protein, l4 g wheat bran, ’ *4 g Oil, Oe4 g emulsifier, 23 g water, 7 g sugar, 2 g salt, 2 g dicalcium phosphate, 3.6 g milk powder (Guy, 1993). The flour content of various flour-containing products, as purchased or as consumed, is shown in Table 7.5. TABLE 7.2 Significant Dates in the History of Flour Bleaching 1901 Andrews patents flour treatment with NO2 (chemical process) 1903 Alsop patents flour treatment with NOZ (electrical treatment) 1909 NO2 in use 1911 Keswick Convention - unmarked flour to be 1921 Benzoyl peroxide first used 1921 J. C. Baker patents NC13 as flour bleacher 1922 NC13 replaces Cl as bleacher for breadmaking flour 1923 Committee appointed to inquire into use of 1924 Committee’s activities extended to chemical 1927 Committee reported that bleaching and improving 1949 NC13 use discontinued in the U.S.A. 1949 C102 first used in the U.S.A. 1955 NC13 use discontinued in the U.K. 1955 C102 first used in the U.K. 1961 Acetone peroxide permitted in the U.S.A. (not in the unbleached preservatives and colouring matter in food substances for flour treatment agents were in use, and that C1, NCI3 and Bz02 were not among those least open to objection U.K.)
FLOUR QUALITY 173 ABLE 7. 4 Proportions of Constituents in recipes for Baked Productss(Relative to Flour: 100 Parts) Type of product Water powder Sugar 1.8 12.5 0.1-2.0 Steak and kidney pudding 0.7 Puff 0.7 Hard sweet 72 0.7 0.5 204 High ratio Wafer batter 3 0.2 0.3 t long Fermentation t mixtures of sodium and ammonium carbonate or bicarbonate S Source: FMBRA. TABLE 7.5 moisture contents(at least 7% and not more than Flour Content of flour-Based Foods, as Purchased or 15.5%, respectively), fat acidity, particle size (98% through a 212 Hm sieve) and protocol Parts of for ash determination. Optional ingredients and Food product per 100 approved additives are listed flour In the U. K, four for human consumption should conform with the nutritional requirements set out in the Bread and Flour Regulations 1984 seml-sweet 67-82 135(cf.p.293) ginger nu For each purpose, flour with particular proper Short pastry 608065155 ties is required: these are secured, in the first ns, scones, teacakes 220 place, by choice of an appropriate wheat grist in terms of strong and weak wheats. The average 84630330 Puddings composition of wheat grists used for milling flour Source: FMBRA Flour wt at natural m.c. Product wt Table 4.8 Table 4.8 also shows that, of the total flour milled in the u.K. in 1990/91, 63% was used for bread, 15% for biscuits, 6% for house- The Codex Alimentarius Commission of the hold use, 2% for cakes, 2% for starch manufacture United Nations Food and Agriculture Organiza- and 12% for other products tion issued standard 152 on flour for human 'Other'food products made with wheat flour consumption in 1985. It defines acceptable sources include pastry, meat pies, sausages, sausage rolls as Triticum aestivum L. bread wheat, and T. rusks, pet foods, baby foods, invalid foods compactum club wheat, the required protein and chapatties, buns, scones, teacakes, pizzas, soups
FLOUR QUALITY 173 TABLE 7.4 Proportions of Constituents in Recipes for Baked Products§ (Relative to Flour: 100 Parts) Constituents Type of product Whole Raising Milk Water Fat Salt egg agent powder Sugar Yeasted products (Yeast) Bread, CBP* 61 0.7 1.8 1.8 Bread, LFPt 57 0.7 1.8 1.1 Cream crackers 32 12.5 1.0 0.1-2.0 Short 25 50 2.0 Pie 31 43 2.0 Steak and kidney pudding 30-36 50 0.7 Puff 40-50 50-70 0.7 Choux 125 50 150 Hard sweet 20 17 0.7 1.1* 2.6 22 Soft 10 32 0.1 0.5$ 2.0 30 Plain 50 40 35 3.5* 40 Pastry Biscuits (whey) Cake High ratio 70 65 2.0 60 5.0* 8 120 Sponge 1.0 170 100 Wafer batter 150 3 0.2 0.3$ * Chorleywood Bread Process. t Long Fermentation Processes. $ Mixtures of sodium and ammonium carbonate or bicarbonate. 5 Source: FMBRA. TABLE 7.5 Flour Content of Flour-Based Foods, as Purchased or Consumed* moisture contents (at least 7% and not more than 15.5%, respectively), fat acidity, particle size (98% through a 212 pm sieve) and protocol for ash determination. Optional ingredients and approved additives are listed. (%) (%) ptflour In the U.K., flour for human consumption should conform with the nutritional requirements - ‘12 90 set out in the Bread and Flour Regulations 1984 semi-sweet 67-82 74 135 (cf. P. 293). ginger nut 43-57 49 205 For each purpose, flour with particular proper- 60-80 65 155 ties is required: these are secured, in the first Bread Short pastry Buns, scones, teacakes 3657 45 220 place, by choice of an appropriate wheat grist in Cakes, pastries, choc. wafer 23-40 33 300 terms of strong and weak wheats. The average uo 25 4oo composition of wheat grists used for milling flour Biscuits (chocolate) Puddings for various purposes in the U.K. is shown in flour milled in the U.K. in 1990/91, 63% was at m.c. of final product. used for bread, 15% for biscuits, 6% for houseThe Codex Alimentarius Commission of the hold use, 2% for cakes, 2% for starch manufacture United Nations Food and Agriculture Organiza- and 12% for ‘other products’. tion issued standard 152 on flour for human ‘Other’ food products made with wheat flour consumption in 1985. It defines acceptable sources include pastry, meat pies, sausages, sausage rolls, as Triticum aestivum L. bread wheat, and T. rusks, pet foods, baby foods, invalid foods, compactum club wheat, the required protein and chapatties, buns, scones, teacakes, pizzas, soups Parts of F1our ‘Ontent product Food product Range Mean per 100 Crispbread Biscuit 53-72 70 145 846 30 330 * Source: FMBU. Flour wt at natural m.c. Product Wt Table 4.8. Table 4.8 also shows that, of the total
174 TECHNOLOGY OF CEREALS frying, chocolate and, quorice, batter(for fish rapidly if the flour is exposed to the action of the ( Ch. 13), premixes, sugar confectionery, cereal air. During such aerated storage, fat acidity convenience foods, snack foods, breakfast cereals, increases at first, owing to lipolytic activity, and puddings, gravy powder, blancmange and brewing later decreases, by lipoxidase action; products of adjunct. Specific requirements for flours for various the oxidation of fatty acids appear; the proportion purposes are outlined below. of linoleic and linolenic acids in the lipids falls; and disulphide bonds(-S-S-)decrease in number. Bread four The change in baking quality, known as matura tion,or ageing,, can be accelerated by chemical The predominance of wheat flour for making improvers,, which modify the physical properties aerated bread is due to the properties of its protein of gluten during fermentation in a way that results which,when the four is mixed with water, forms in bread of better quality being obtained. Matured in elastic substance called gluten(cf. Chs 3 and flour differs from freshly milled flour in that it 8). This property is found to a slight extent in has better handling properties, increased tolerance rye but not in other cereals in the dough to varied conditions of fermentation The property of producing a loaf of relatively and in producing loaves of larger volume and large volume, with regular, finely vesiculated more finely textured crumb crumb structure, is possessed by flours milled Improving agents permitted in the U. K. Bread from wheats described as'strong'(cf Chs 4 and and Flour Regulations 1984(SI1984, No 1304), as 8). Protein strength is an inherent characteristic, amended by the Potassium Bromate(prohibitic but the amount of protein present can be influenced as a Flour Improver)Regulations 1990(SI 1990 by the conditions under which wheats are grow No. 399)are chlorine,(for cake flour only; not Protein content is also an important determinant wholemeal), cysteine hydrochloride(920)(all of bread quality, there being a positive correlation flour except wholemeal), chlorine dioxide (all between loaf specific volume(ml/g) and the flour except wholemeal), L-ascorbic acid(vitamin percentage of protein present C)(all flour except wholemeal; all bread), and Typical characteristics of Chorleywood Bread azodicarbonamide(all four except wholemeal Process(CBP)four, Bakers'flour(as used in Besides their improving effect, these substances the bulk fermentation process), and rollermilled give a whitened appearance to the loaf because wholemeal in the U.K. are shown in Table 7.6. of their beneficial effect on the texture of the crumb. Improving agents do not increase the Maturing and improving agen carbon dioxide production in a fermented dough, but they improve gas retention(because the The breadmaking quality of milled dough is made more elastic) and this results in flour tends to improve during storage for a period increased loaf volume(cf. Ch. 8) of 1-2 months. The improvement occurs more TABLE 7.6 Redox improvers Typical U. K. Bread Flour Analysis 1992 The action of improvers is believed to be an cBP Bakers'Wholemeal oxidation of the cysteine sulphydryl or thiol Moisture 1 6% 14 5% 14.6% (-SH) groups present in wheat gluten As a result, 14.7% these thiol groups are no longer available for grade colour participation in exchange reactions with disulphide 2FU 2IFU (S-S-)bonds-a reaction which is conside ed to 34FU release the stresses in dough -and consequently Water absorption 60.2% 62.0% 70 2% the dough tightens, i. e the extensibility is reduced Farrand units, (includes fungal enzyme Alternatively, it has been suggested that the oxidation of- sh groups may lead to the formation
174 TECHNOLOGY (Ch. 13), premixes, liquorice, batter (for fish frying), chocolate and sugar confectionery , cereal convenience foods, snack foods, breakfast cereals, puddings, gravy powder, blancmange and brewing adjunct. Specific requirements for flours for various purposes are outlined below. Bread flour The predominance of wheat flour for making aerated bread is due to the properties of its protein which, when the flour is mixed with water, forms an elastic substance called gluten (cf. Chs 3 and 8). This property is found to a slight extent in rye but not in other cereals. The property of producing a loaf of relatively large volume, with regular, finely vesiculated crumb structure, is possessed by flours milled from wheats described as 'strong' (cf. Chs 4 and 8). Protein strength is an inherent characteristic, but the amount of protein present can be influenced by the conditions under which wheats are grown. Protein content is also an important determinant of bread quality, there being a positive correlation between loaf specific volume (ml/g) and the percentage of protein present. Typical characteristics of Chorleywood Bread Process (CBP) flour, Bakers' flour (as used in the bulk fermentation process), and rollermilled wholemeal in the U .K. are shown in Table 7.6. Maturing and improving agents The breadmaking quality of freshly milled flour tends to improve during storage for a period of 1-2 months. The improvement occurs more TABLE 7.6 Typical U.K. Bread Flour Analysis 1992 Redox improvers The action of improvers is believed to be an oxidation of the cysteine sulphydryl or thiol ( -8H) groups present in wheat gluten. As a result, these thiol groups are no longer available for participation in exchange reactions with disulphide ( -8-8- ) bonds -a reaction which is considered to release the stresses in dough -and consequently the dough tightens, i.e. the extensibility is reduced. Alternatively, it has been suggested that the oxidation of -8H groups may lead to the formation CBP Bakers' Wholemeal 14.6% 11.0% 2.1 329 lSFU 30FU 60.2% 14.5% 12.1% 2.2 334 22FU 34FU 62.0% 14.6% 14.7% Moisture Protein Grade colour Falling number alpha-Amylase* Starch damage Water absorption 330 21FU 70.2% * Farrand units, (includes fungal enzyme). Source: FMBRA. OF CEREALS rapidly if the flour is exposed to the action of the air. During such aerated storage, fat acidity increases at first, owing to lipolytic activity, and later decreases, by lipoxidase action; products of the oxidation of fatty acids appear; the proportion of linoleic and linolenic acids in the lipids falls; and disulphide bonds ( -S-S- ) decrease in number . The change in baking quality , known as maturation, or 'ageing', can be accelerated by chemical 'improvers', which modify the physical properties of gluten during fermentation in a way that results in bread of better quality being obtained. Matured flour differs from freshly milled flour in that it has better handling properties, increased tolerance in the dough to varied conditions of fermentation and in producing loaves of larger volume and more finely textured crumb. Improving agents permitted in the U .K. Bread and Flour Regulations 1984 (SI1984, No.1304), as amended by the Potassium Bromate (Prohibition as a Flour Improver) Regulations 1990 (SI 1990, No.399) are chlorine, (for cake flour only; not wholemeal), cysteine hydrochloride (920) (all flour except wholemeal), chlorine dioxide (all flour except wholemeal), L-ascorbic acid (vitamin C) (all flour except wholemeal; all bread), and azodicarbonamide (all flour except wholemeal). Besides their improving effect, these substances give a whitened appearance to the loaf because of their beneficial effect on the texture of the crumb. Improving agents do not increase the carbon dioxide production in a fermented dough, but they improve gas retention (because the dough is made more elastic) and this results in increased loaf volume (cf. Ch. 8)
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 the
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 (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 coundeletion 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 breadit 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 circumcarbonate 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 retenbromine (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
176 TECHNOLOGY OF CEREALS Netherlands, 200 mg/kg in Canada, Denmark, other than wholemeal; higher levels(up to Italy, Spain, the U.S.A. and the U. K, 300 mg/kg 300 mg/kg)are permitted in certain biscuit fours in France. No maximum level is specified in Use of L-cysteine is permitted in Denmark(up Australia, Greece, Portugal, Germany since to 25 mg/kg), Germany(up to 30 mg/kg), belgium ascorbic acid is reckoned to be quite safe, although (up to 50 mg/kg), Australia, New Zealand and it is under scrutiny by the COt. Use of ascorbic the Netherlands(up to 75 mg/kg), Canada (up to acid is also permitted in Japan, New Zealand and 90 mg/kg) and Sweden (up to 100 mg/kg) Sweden L-Cysteine is not mentioned as a permitted addi NH2CONNCONH2;ADA,)is a flour maturing Portugal, Spain or the U.S.A,V,, luxembourg Azodicarbonamide (1, l'azobisfc formamide tive in Fr ent aturox Cysteine accelerates reactions within and as 'ADA 20%'CAK20).'Maturox' contains between molecules in the dough which lead to an either 10% or 20% of ADA; ' Genitron'contains improvement in its viscoelastic and gas- holding 20% or 50% of ADA, dispersed in an excipient, properties. These reactions normally take place generally calcium sulphate and magnesium car- slowly during bulk fermentation but with the bonate. The particle size of Ada is generally 3- addition of cysteine the bulk fermentation period 5 um. It was first used in the U.S.A. in 1962 can be eliminated. Cysteine, which is a rapi (maximum permitted level 45 mg/kg on flour acting reducing agent, is used in the ADd weight). When mixed into doughs it oxidizes the conjunction with slow-acting oxidizing agents, ulphydryl(-SH) groups and exerts an improving such as ascorbic acid and potassium bromate action. Oxidation is rapid and almost complete (where permitted) or azodicarbonamide, which in doughs mixed for 2.5 min Short mixing times complete the 'activation' commenced by the are thus appropriate. The residue left in the flour cysteine. The dough-softening action of cysteine oduce drier, more cohesive dough than that of fully developed dough e is biurea. flour treated with ada is said reduces the work input required for the production treated with chlorine dioxide, to show superiority in mixing properties, and to tolerate higher water Blending for improver treatment absorption. An average treatment rate is 5 mg/kg n four weight) in bulk fermentation and low The principles applied to bleaching fours of peed mixing methods of baking, and 20-25 different grades also apply to improver treatment mg/kg(on flour weight) in the high-speed mixing (cf. Table 7.1). Chorleywood Bread Process(CBP). The agent does not bleach, but the bread made from treated Emulsifiers and stabilizers structure. The use of ADa has been permitted, to 'Emulsifiers'and'stabilizers'are any substances a maximum level of 45 mg/kg, in the U. K. since capable of aiding formation of (emulsifiers )or 1972. Its usage is also permitted in Canada, New maintaining(stabilizers) the uniform dispersion Zealand and the u.s.A. but not in Australia or of two or more immiscible substances. Flours, in EC countries other than the U. K.(1989) sold as such. are not allowed to contain emulsifiers L-Cysteine is a naturally occurring amino acid, but the following are permitted by the bread and is used in the Activated Dough Development Flour Regulations(1984)to be included in bread: process(ADD)(cf Ch 8), in which it functions E 322 lecithins; E460 a-cellulose(permitted only as a reducing agent The addition of L-cysteine in bread for which a slimming claim is made); (in the form of L-cysteine hydrochloride or E466 carboxymethyl cellulose, sodium salt(per L-cysteine hydrochloride monohydrate) to bread mitted only in bread for which a slimming claim doughs, for this purpose, is permitted by the is made); E471 mono- and di-glycerides of fatty Bread and Flour Regulations 1984 in the U. K. acids; E472(b) lactic acid esters of mono- and to a maximum level of 75 mg/kg in bread flours di-glycerides of fatty acids; E472(c) citric acid
176 TECHNOLOGY OF CEREALS Netherlands, 200 mg/kg in Canada, Denmark, other than wholemeal; higher levels (up to Italy, Spain, the U.S.A. and the U.K., 300 mg/kg 300 mg/kg) are permitted in certain biscuit flours. in France. No maximum level is specified in Use of L-cysteine is permitted in Denmark (up Australia, Greece, Portugal, Germany since to 25 mg/kg), Germany (up to 30 mg/kg), Belgium ascorbic acid is reckoned to be quite safe, although (up to 50 mg/kg), Australia, New Zealand and it is under scrutiny by the COT. Use of ascorbic the Netherlands (up to 75 mg/kg), Canada (up to acid is also permitted in Japan, New Zealand and 90 mg/kg) and Sweden (up to 100 mg/kg). Sweden. L-Cysteine is not mentioned as a permitted addiAzodicarbonamide (1,l ’azobisformamide; tive in France, Greece, Italy, Luxembourg, NH2CONNCONH2; ‘ADA’) is a flour maturing Portugal, Spain or the U.S.A. agent, marketed as ‘Maturox’, or ‘Genitron’, or Cysteine accelerates reactions within and as ‘ADA 20%’ (‘AK20’). ‘Maturox’ contains between molecules in the dough which lead to an either 10% or 20% of ADA; ‘Genitron’ contains improvement in its viscoelastic and gas-holding 20% or 50% of ADA, dispersed in an excipient, properties. These reactions normally take place generally calcium sulphate and magnesium car- slowly during bulk fermentation but with the bonate. The particle size of ADA is generally 3- addition of cysteine the bulk fermentation period 5 pm. It was first used in the U.S.A. in 1962 can be eliminated. Cysteine, which is a rapid- (maximum permitted level 45 mg/kg on flour acting reducing agent, is used in the ADD in weight). When mixed into doughs it oxidizes the conjunction with slow-acting oxidizing agents, sulphydryl (-SH) groups and exerts an improving such as ascorbic acid and potassium bromate action. Oxidation is rapid and almost complete (where permitted) or azodicarbonamide, which in doughs mixed for 2.5 min. Short mixing times complete the ‘activation’ commenced by the are thus appropriate. The residue left in the flour cysteine. The dough-softening action of cysteine is biurea. Flour treated with ADA is said to reduces the work input required for the production produce drier, more cohesive dough than that of fully developed dough. treated with chlorine dioxide, to show superiority in mixing properties, and to tolerate higher water Blending for improver treatment absorption. An average treatment rate is 5 mg/kg (on flour weight) in bulk fermentation and low- The principles applied to bleaching flours of speed mixing methods of baking, and 20-25 different grades also apply to improver treatment mg/kg (on flour weight) in the high-speed mixing (cf. Table 7.1). Chorleywood Bread Process (CBP). The agent Emulsifiers and stabilizers does not bleach, but the bread made from treated flour appears whiter because of its finer cell structure. The use of ADA has been permitted, to ‘Emulsifiers’ and ‘stabilizers’ are any substances a maximum level of 45 mg/kg, in the U.K. since capable of aiding formation of (emulsifiers) or 1972. Its usage is also permitted in Canada, New maintaining (stabilizers) the uniform dispersion Zealand and the U.S.A., but not in Australia or of two or more immiscible substances. Flours, in EC countries other than the U.K. (1989). sold as such, are not allowed to contain emulsifiers L-Cysteine is a naturally occurring amino acid, but the following are permitted by the Bread and is used in the Activated Dough Development Flour Regulations (1984) to be included in bread: process (ADD) (cf. Ch. 8), in which it functions E 322 lecithins; E460 a-cellulose (permitted only as a reducing agent. The addition of L-cysteine in bread for which a slimming claim is made); (in the form of L-cysteine hydrochloride or E466 carboxymethyl cellulose, sodium salt (perL-cysteine hydrochloride monohydrate) to bread mitted only in bread for which a slimming claim doughs, for this purpose, is permitted by the is made); E471 mono- and di-glycerides of fatty Bread and Flour Regulations 1984 in the U.K. acids; E472(b) lactic acid esters of mono- and to a maximum level of 75 mg/kg in bread flours di-glycerides of fatty acids; E472(c) citric acid
FLOUR QUALITY 17 esters of mono-and di-glycerides of fatty acids; coarse a four produces incomplete sheets of E472(e)mono-and di-acetyl tartaric acid esters of unsatisfactory wafers mono-and di- glycerides of fatty acids; E481 Gluten development in wafer batters must be sodium stearoyl-2-lactylate (cf. Ch. 8); E482 avoided, so flours which have a low tendency to calcium stearoyl-2-lactylate; E483 stearyl tartrate; give an aggregated gluten under low shear rates E481 and E482 are subject to a maximum level in aqueous flour batters are required Hence low of 5000 mg/kg protein flours with weak extensible glutens are normally specified(cf. p. 186) Biscuit cookie, cracker) flour Cracker doughs have fully developed gluten networks and protein quality is important in Biscuit flours for short and semi-sweet biscuits dough processing Cracker fours w um are typically produced from grists containing protein contents(9.5-10.5%)made mainly soft wheats, with some hard wheats hard wheats are commonly used included to increase the rate of production in the water biscuits made from unbleached, untreated mill. However, hard wheat flours produce thinner four and water only biscuits than those of soft wheats so it is important to use a narrow range of levels of hard wheat in the flour. The level specified will depend on the Emulsifiers manufacturers preference since the biscuit plant Emulsifiers are used in biscuits, either as will have to produce biscuits of particular sizes processing aids or as partial replacements for fat and weights to suit the packing plant Very low levels(e.g 0. 1%on fat basis) of sodium There is no developed gluten network in short stearoyl-2-lactylate (E481)in sheeted biscuit biscuit doughs, hence neither the level nor quality doughs produce a smooth, non-sticky surface of protein is significant in production. However, which aids dough-piece cutting Lecithin(E322) consistency of quality is critically important in is commonly used in wafer batters to aid release of modern, high-speed production plants. Flours the baked wafer from the wafer baking machinery. would normally be specified to have, say, a range Emulsifiers which can replace a substantial propor- of 1% protein within the typical range for flours tion of fat in biscuits without serious deterioration (8-10%) in product quality are sodium stearoyl-2-lactylate Semi-sweet biscuits have a developed gluten and the diacetyltartaric acid esters of mono- network which is modified during processing, glycerides of fatty acids E472e. Lecithin and for these biscuits low protein flours(typically used to replace a low level of fat in biscuits 8.5-9.5%)with weak, extensible glutens are used At present, sulphur dioxide(SO2, usually obtained from sodium metabisulphite added at the mixer Flours for confectionery products is used to increase the extensibility and decrease the elasticity of the doughs. This aids control of Cake flours the dough sheet and hence biscuit thickness. ec Flour in cakes should allow an aerated structure proposals include permission of SO2 in fine to be retained after the cake has been built up bakery wares, up to 50 mg/kg in the final product. The stability of the final cake depends largely Nevertheless wheat breeders are seeking to develop upon the presence of uniformly swollen starch varieties which perform well without its use granules; hence, the granules should be undamaged For wafers, low protein flour milled from weak during milling, free from adherent protein wheat is suitable. Particle size is an important unattacked by amylolytic enzymes. These charac characteristic; ideally about 55% should be below teristics are found in four milled from a soft 40 um, 35%between 40 and 90 um, and not more low-protein wheat of low alpha-amylase activity than 10% coarser than 90 um. Too fine a flour Typical parameter values for cake flour milled produces light, tender, fragile wafers, while too in the U. K. would be as follows: Untreated cake
FLOUR QUALITY 177 esters of mono- and di-glycerides of fatty acids; coarse a flour produces incomplete sheets of E472(e) mono- and di-acetyl tartaric acid esters of unsatisfactory wafers. mono- and di-glycerides of fatty acids; E481 Gluten development in wafer batters must be sodium stearoyl-2-lactylate (cf. Ch. 8); E482 avoided, so flours which have a low tendency to calcium stearoyl-2-lactylate; E483 stearyl tartrate; give an aggregated gluten under low shear rates E481 and E482 are subject to a maximum level in aqueous flour batters are required. Hence low of 5000 mg/kg. protein flours with weak extensible glutens are normally specified (cf. p. 186). Cracker doughs have fully developed gluten networks and protein quality is important in Biscuit (cookie, cracker) flour Biscuit flours for short and semi-sweet biscuits dough processing. Cracker flours with medium are typically produced from grists containing protein contents (9.5-10.5%) made mainly from mainly soft wheats, with some hard wheats hard wheats are commonly used. Matzos are included to increase the rate of production in the water biscuits made from unbleached, untreated mill. However, hard wheat flours produce thinner flour and water only. biscuits than those of soft wheats so it is important Emulsifiers to use a narrow range of levels of hard wheat in the flour. The level specified will depend on the manufacturer’s preference since the biscuit plant Emulsifiers are used in biscuits, either as will have to produce biscuits of particular sizes processing aids or as partial replacements for fat. and weights to suit the packing plant. Very low levels (e.g. 0.1% on fat basis) of sodium There is no developed gluten network in short stearoyl-2-lactylate (E48 1) in sheeted biscuit biscuit doughs, hence neither the level nor quality doughs produce a smooth, non-sticky surface of protein is significant in production. However, which aids dough-piece cutting. Lecithin (E322) consistency of quality is critically important in is commonly used in wafer batters to aid release of modern, high-speed production plants. Flours the baked wafer from the wafer baking machinery. would normally be specified to have, say, a range Emulsifiers which can replace a substantial proporof 1% protein within the typical range for flours tion of fat in biscuits without serious deterioration (8-1 0%). in product quality are sodium stearoyl-2-lactylate Semi-sweet biscuits have a developed gluten and the diacetyltartaric acid esters of mononetwork which is modified during processing, glycerides of fatty acids E472e. Lecithin can be and for these biscuits low protein flours (typically used to replace a low level of fat in biscuits. 8.5-9.5%) with weak, extensible glutens are used. Flours for confectionery products At present, sulphur dioxide (SO*, usually obtained from sodium metabisulphite added at the mixer) Cake flours is used to increase the extensibility and decrease the elasticity of the doughs. This aids control of the dough sheet and hence biscuit thickness. EC Flour in cakes should allow an aerated structure proposals include permission of SO2 in fine to be retained after the cake has been built up. bakery wares, up to 50 mg/kg in the final product. The stability of the final cake depends largely Nevertheless wheat breeders are seeking to develop upon the presence of uniformly swollen starch varieties which perform well without its use. granules; hence, the granules should be undamaged For wafers, low protein flour milled from weak during milling, free from adherent protein, and wheat is suitable. Particle size is an important unattacked by amylolytic enzymes. These characcharacteristic; ideally about 55% should be below teristics are found in flour milled from a soft, 40 pm, 35% between 40 and 90 pm, and not more low-protein wheat of low alpha-amylase activity. than 10% coarser than 90 pm. Too fine a flour Typical parameter values for cake flour milled produces light, tender, fragile wafers, while too in the U.K. would be as follows: Untreated cake
178 TECHNOLOGY OF CEREALS four:8.5-9.5% protein and a minimum of particles at a level of about 0.5-1.0% of batter weight, exceeding 90 um in size. Fine particle size is more whisking times can be greatly reduced, all-in important than low protein content for cake mixing methods can be used and liquid egg can quality, giving finer, more even crumb than that be replaced with dried eg given by a coarser four Foam-promoting emulsifiers such as GMS Strong cake four (for fruit cakes ): 12% poly-glycerol esters, propylene-glycol esters(E477) protein, 20-25 FU starch damage, 0.18% chlorine or blends of these, used at about 1% of batter treatment weight, allow a reduction in the fat content of a cake or even substitution of the fat by a smaller High-ratio flour quantity of vegetable oil Although anti-staling effects of emulsifiers in In the late 1920s it was discovered, in the cakes are not as clearly defined as in bread U.S.A that cake four which had been bleached sucrose esters(E473), sodium stearoyl lactylate with chlorine gas to improve its colour permitted (E481)and poly-glycerol esters(E475)offer some production of cakes from formulae containing possibilities as a means of minimizing the effects levels of sugar and liquid each of which is in of staling excess of four weight. Such flour for use in high sugar/flour ratio and high liquid/flour ratio formulae is known as high-ratio four. It should flour for cake premixes also have fine, uniform granularity and low protein Some cake premixes sold in britain contain, in ontent. The chlorination treatment, generally powder form, all the ingredients required for a 0. 1-0.15% by weight, besides allowing addition cake, vis. flour, fat, sugar, baking powder, milk of larger proportions of liquid and sugar, reduces powder, eggs, flavouring and colour, and need only elasticity of the gluten and lowers the pH to 4.6- the addition of water before baking. However, 5.1 some cake premixes, particularly those sold in the Heat treatment of the grain or of the semolina U.S.A. omit the eggs and/or the milk, because from which the four is milled has been found to lighter cakes of larger volume can be made by the be an effective substitute for the chlorine treat- use of fresh eggs instead of dried ingredients ment of high-ratio cake flour(BP nos 1444173 The type of four must be suitable for the (FMBRA)and 1499 986. Lyons))(cf. p 171) particular product, flours of high-ratio type gener and cake fours may be similarly treated ally being used. The fat must have the correct Typical characteristics of high-ratio flour milled plasticity and adequate stability to resist oxida in the u. K. would be 7.6-8.4% protein, 20-25 FU tion. The addition of certain antioxidants to fat starch damage, granularity such that 70% of the to improve stability, is allowed in Britain, the particles were below 32 um in size and a minimum U.S.A. and elsewhere. Those allowed in britain of particles exceeding 90 um in size. High-ratio under the Antioxidants in Food Regulations 1978 four is particularly suitable for sponge-type goods. (S I 1978 No. 105, as amended) for addition to anhydrous oils and fats, and certain dairy products Emulsifiers in cakes other than butter, for use as ingredients are propyl, octyl or dodecyl gallates up to 100 mg/kg In cake making, emulsifiers such as glycerol or butylated hydroxyanisole (BHA)and/or monostearate( GMS)and mono-and di-glycerides butylated hydroxytoluene (BHT) up to 200 of fatty acids(e471)are used in soft fats at levels mg/kg(calculated on the fat). Those allowed in of up to 10% to produce high-ratio shortenings. the U.S. A (with permitted levels based on fat or Certain emulsifiers such as GMs, polyglycerol oil content) are: resin guaiac(0. 1%), tocopherols esters and lactic acid esters of mono-glycerides (0.03%), lecithin(0.01%), citric acid(0.01%), (E472b) possess remarkable foam-promoting pyrogallate (0.01%), propylgallate(0.02%)and properties so that when added to sponge batters bha and/or Bht(0.02%)
178 TECHNOLOGY OF CEREALS flour: 8.5-9.5% protein and aminimum of particles at a level of about 0.5-1 .O% of batter weight, exceeding 90 pm in size. Fine particle size is more whisking times can be greatly reduced, all-in important than low protein content for cake mixing methods can be used and liquid egg can quality, giving finer, more even crumb than that be replaced with dried egg. given by a coarser flour. Foam-promoting emulsifiers such as GMS, Strong cake flour (for fruit cakes): 12% poly-glycerol esters, propylene-glycol esters (E477) protein, 20-25 FU starch damage, 0.18% chlorine or blends of these, used at about 1% of batter treatment. weight, allow a reduction in the fat content of a cake or even substitution of the fat by a smaller quantity of vegetable oil. Although anti-staling effects of emulsifiers in High-ratio flour In the late 1920s it was discovered, in the cakes are not as clearly defined as in bread, U.S.A., that cake flour which had been bleached sucrose esters (E473), sodium stearoyl lactylate with chlorine gas to improve its colour permitted (E481) and poly-glycerol esters (E475) offer some production of cakes from formulae containing possibilities as a means of minimizing the effects levels of sugar and liquid each of which is in of staling. excess of flour weight. Such flour for use in high sugar/flour ratio and high liquid/flour ratio Flour for cake premixes formulae is known as ‘high-ratio flour’. It should also have fine, uniform granularity and low protein Some cake premixes sold in Britain contain, in content. The chlorination treatment, generally powder form, all the ingredients required for a 0.1-0.15% by weight, besides allowing addition cake, viz. flour, fat, sugar, baking powder, milk of larger proportions of liquid and sugar, reduces powder, eggs, flavouring and colour, and need only elasticity of the gluten and lowers the pH to 4.6- the addition of water before baking. However, 5.1. some cake premixes, particularly those sold in the Heat treatment of the grain or of the semolina U.S.A., omit the eggs and/or the milk, because from which the flour is milled has been found to lighter cakes of larger volume can be made by the be an effective substitute for the chlorine treat- use of fresh eggs instead of dried ingredients. ment of high-ratio cake flour (BP nos 1444173 The type of flour must be suitable for the (FMBRA) and 1499 986 (J. Lyons)) (cf. p.171) particular product, flours of high-ratio type generand cake flours may be similarly treated. ally being used. The fat must have the correct Typical characteristics of high-ratio flour milled plasticity and adequate stability to resist oxidain the U.K. would be 768.4% protein, 2&25 FU tion. The addition of certain antioxidants to fat, starch damage, granularity such that 70% of the to improve stability, is allowed in Britain, the particles were below 32 pm in size and a minimum U.S.A. , and elsewhere. Those allowed in Britain of particles exceeding 90 pm in size. High-ratio under the Antioxidants in Food Regulations 1978 flour is particularly suitable for sponge-type goods. (S.1 1978 No. 105, as amended) for addition to anhydrous oils and fats, and certain dairy products other than butter, for use as ingredients are propyl, octyl or dodecyl gallates up to 100 mg/kg, Emulsifiers in cakes In cake making, emulsifiers such as glycerol or butylated hydroxyanisole (BHA) and/or monostearate (GMS) and mono- and di-glycerides butylated hydroxytoluene (BHT) up to 200 of fatty acids (E471) are used in soft fats at levels mg/kg (calculated on the fat). Those allowed in of up to 10% to produce high-ratio shortenings. the U.S.A. (with permitted levels based on fat or Certain emulsifiers such as GMS, polyglycerol oil content) are: resin guaiac (0.1%), tocopherols esters and lactic acid esters of mono-glycerides (0.03%), lecithin (0.01%)) citric acid (0.01%), (E472b) possess remarkable foam-promoting pyrogallate (0.01%), propylgallate (0.02%) and properties so that when added to sponge batters BHA and/or BHT (0.02%)
FLOUR QUALITY In preparing the premixes, the dry ingredients wheat has been denatured it is not suitable for are measured out by automatic measures and breadmaking. The flour may, for many purposes, conveyed, often pneumatically, to a mixing bin, be regarded as impure starch, and is often used mixed, and then entoleted(cf. p. 111) to ensure to replace starch in certain types of adhesives freedom from insect infestation. The fat is then and as a filler for meat products added, and the mixture packaged. If fruit is The bacteriological status of flour for soups is included in the formula, it is generally contained important and requires not >125 total thermo- in a separate cellophane-wrapp kage enclosed philic spores per 10 g, not >50 flat sour spores per in the carton 10 g, not>5 sulphide spoilage organisms per 10 g, hemophilic anaerobic spores in not >3 tubes out of 6 Flour for fermented goods For buns, etc. a breadmaking four is require ermentation time is short; the fat and the sugar Quellmehl in the formula bring about shortening of the Quellmehl or heat-treated starch, is defined gluten maize four or wheat flour of which the starch has undergone hydrothermic(viz. steam)treat Flour for pastry ment resulting in pregelatinization of the starch thereby increasing its swelling capacity by at least A weak, medium strength four is needed for 50% the production of sweet and savoury short pastes Flour strength for puff pastry will vary according Flour for sausage rusk to the processing methods, with rapid processing methods requiring weaker flours than those usee A low protein flour milled from weak wheat in traditional methods of production. In general, such as U. K.-grown Riband, or a low protein air- flours for puff pastry should have low resistance classified fraction is required. Desirable charac- to deformation (e.g. low Brabender resistance teristics are low maltose figure(not >1.4 by Blish values) but reasonable extensibi and Sandstedt method), low alpha-amylase activity (high Falling Number) and high absorbency Flour from steamed whea Flour milled from steamed wheat(stabilized Batter flour flour, in which enzymes have been inactivated) A low protein flour milled from a grist com is produced for use in manufacture of soups( Ch. prising 90%weak British wheat plus 10% strong 7), gravies, crumpets, liquorice and as a thickening wheat is suitable. Alpha-amylase activity should agent. For these purposes, the flour should form be low. Too high a viscosity in the batter caused a thick paste when it is heated with water, and by excessive starch damage is to be avoided, and the paste should retain its consistency for some therefore the proportion of hard wheat in the grist time when heated at 90-95.. The alpha-amylase should be restricte activity of normal(non-steam-treated)flour is granules during the cooking process, resulting in Household flour water-bindi ng capacity and formation of Household flour is used for making puddings thin pastes of low apparent viscosity. The greater cakes, pastry, etc. In the U. K. it is milled from a water-absorbing capacity of the flour from steamed grist consisting predominantly of weak wheats of wheat could also make it a suitable ingredient for low protein, such as British or Western European, canned pet-foods with admixture of up to 20% of strong wheat to As the gluten in the flour from steam-treated promote flowability and good mixing. Exclusion
FLOUR QUALITY 179 wheat has been denatured it is not suitable for breadmaking. The flour may, for many purposes, be regarded as impure starch, and is often used to replace starch in certain types of adhesives, and as a filler for meat products. The bacteriological status of flour for soups is important and requires not > 125 total thermophilic spores per 10 g, not >50 flat sour spores per 10 g, not >5 sulphide spoilage organisms per 10 g, thermophilic anaerobic spores in not >3 tubes out of 6. Quellmehl Quellmehl or heat-treated starch, is defined as maize flour or wheat flour of which the starch has undergone hydrothermic (vzz. steam) treatment resulting in pregelatinization of the starch thereby increasing its swelling capacity by at least 50%. Flour for sausage rusk A low protein flour milled from weak wheat, such as U.K.-grown Riband, or a low protein airclassified fraction is required. Desirable characteristics are low maltose figure (not > 1.4 by Blish and Sandstedt method), low alpha-amylase activity (high Falling Number) and high absorbency. Batter flour A low protein flour milled from a grist comprising 90% weak British wheat plus 10% strong wheat is suitable. Alpha-amylase activity should be low. Too high a viscosity in the batter caused by excessive starch damage is to be avoided, and therefore the proportion of hard wheat in the grist should be restricted. Household flour Household flour is used for making puddings, cakes, pastry, etc. In the U.K. it is milled from a grist consisting predominantly of weak wheats of low protein, such as British or Western European, with admixture of up to 20% of strong wheat to promote flowability and good mixing. Exclusion In preparing the premixes, the dry ingredients are measured out by automatic measures and conveyed, often pneumatically, to a mixing bin, mixed, and then entoleted (cf. p. 111) to ensure freedom from insect infestation. The fat is then added, and the mixture packaged. If fruit is included in the formula, it is generally contained in a separate cellophane-wrapped package enclosed in the carton. Flour for fermented goods For buns, etc. a breadmaking flour is required. Fermentation time is short; the fat and the sugar in the formula bring about shortening of the gluten. Flour for pastry A weak, medium strength flour is needed for the production of sweet and savoury short pastes. Flour strength for puff pastry will vary according to the processing methods, with rapid processing methods requiring weaker flours than those used in traditional methods of production. In general, flours for puff pastry should have low resistance to deformation (e.g. low Brabender resistance values) but reasonable extensibility. Flour from steamed wheat Flour milled from steamed wheat ('stabilized' flour, in which enzymes have been inactivated) is produced for use in manufacture of soups (Ch. 7), gravies, crumpets, liquorice and as a thickening agent. For these purposes, the flour should form a thick paste when it is heated with water, and the paste should retain its consistency for some time when heated at 9Oo-95"C. The alpha-amylase activity of normal (non-steam-treated) flour is usually high enough to degrade swollen starch granules during the cooking process, resulting in loss of water-binding capacity and formation of thin pastes of low apparent viscosity. The greater water-absorbing capacity of the flour from steamed wheat could also make it a suitable ingredient for canned pet-foods. As the gluten in the flour from steam-treated