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 formation174 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 matura￾tion, 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)