TECHNOLOGY OF CEREALS rom Aspergillus oryzae or A. awamori, to the flour Both alpha- and beta-amylases catalyze the (cf. p. 196). Fungal amylase is preferred to malt flour because the thermal inactivation temperature hydrolysis of starch, but in different ways(cf p. of fungal amylase is lower (75.C) than that of 67) Normal four from sound wheat alpha-amylase. The amount of alpha-amylase, the consequent difficulties in slicing bread with however,increases considerably when wheat a sticky crumb Gas retention is a property of the flour protein germinates. Indeed, flour from wheat containing the gluten, while being sufficiently extensible to many sprouted grains may have too high an alpha- allow the loaf to rise, must yet be strong enough to prevent gas escaping too readily, as this would nB, some of the starch is changed into dextrin-like lead to collapse of the loaf. The interaction of he crumb is weakened, and the dextrins make the crumb sticky(cf. p 67). However, flour with too powerful effect on gas retention high a natural alpha-amylase activity could be used for making satisfactory bread by microwave Dough development or radio-frequency baking methods(cf. p. 206) Another possibility would be to make use of an Protein alpha-amylase inhibitor, e.g. one prepared from The process of dough development, which barley, as described in Canadian Patent No 1206157 of 1987(Zawistowska et al. 1988). occurs during dough ripening, concerns the The functions of starch in the baking of bread hydrated protein component of the flour. It are to dilute the gluten to a desirable consistenc involves an uncoiling of the protein molecules to provide sugar through diastasis, to provide a and their joining together, by cross-linking, to strong union with gluten, and by gelatinization form a vast network of protein which is collec- to become flexible and to take water from the tively called gluten. The coils of the protein gluten, a process which helps the gluten film to molecules are held together by various types of et and become rigid bonds, including disulphide(Ss-) bonds, and it is the severing of these bonds -allowing the molecule to uncoil- and their rejoining in Gas production and gas retention different positions linking separate protein molecules together that constitutes a major The creation of bubble structure in the dough part of dough development is a fundamental requirement in breadmaking Sulphydryl (SH) groups(cf. pp 66, 174)are The carbon dioxide generated by yeast activity also present in the protein molecules as side groups does not create bubbles: it can only inflate gas of the amino acid cysteine. Reaction between the cells already formed by the incorporation of air -SH groups and the-SS-bonds permits new inter- during mixing and intra-protein/polypeptide relationships to be equate gas must be produced during fermen- formed via-Ss-bonding, one effect of this inter- tation, otherwise the loaf will not be inflated suf- change being the relaxation of dough by the relief ficiently Gas production depends on the quantity of stress induced by the mixing process of soluble sugars in the flour, and on its diastatic While gluten is important in creating an extens- power. Inadequate gassing (maltose value less ible framework, soluble proteins in the dough than 1.5) may be due to an insufficiency of liquor may also contribute to gas retention by damaged starch or to a lack of alpha-amylase; the forming an impervious lining layer within cells latter can be corrected by adding sprouted wheat effectively blocking pin- holes in cell walls( Gar to the grist, or malt four, or fungal amylase, e.g. et al., 1990)198 TECHNOLOGY OF CEREALS Amylase from Aspergillus oryzae or A. awamori, to the flour (cf. p. 196). Fungal amylase is preferred to malt flour because the thermal inactivation temperature cereal alpha-amylase (87"C), and its use avoids the the consequent difficulties in slicing bread with a sticky crumb. Gas retention is a property of the flour protein: the gluten, while being sufficiently extensible to to prevent gas escaping too readily, as this would lead to collapse of the loaf. The interaction of added fat with flour components also has a powerful effect on gas retention. Dough development Protein The process of dough development, which occurs during dough ripening, cOncernS the hydrated protein component of the flour. It involves an uncoiling of the protein molecules and their joining together, by cross-linking, to form a vast network of protein which is collec￾tively called gluten. The coils of the protein molecules are held together by various types of it is the severing of these bonds - allowing the molecule to uncoil - and their rejoining in different positions - linking separate protein molecules together - that constitutes a major part of dough development. Sulphydryl (-SH) groups (cf. pp. 66, 174) are also present in the protein molecules as side groups of the amino acid cysteine. Reaction between the -SH groups and the -SS- bonds permits new inter￾and intra-proteidpolypeptide relationships to be formed via -SS- bonding, one effect of this inter￾change being the relaxation of dough by the relief of stress induced by the mixing process. While gluten is important in creating an extens￾ible framework, soluble proteins in the dough liquor may also contribute to gas retention by forming an impervious lining layer within cells, effectively blocking pin-holes in cell walls (Gan et al., 1990). Both alpha- and beta-amylases catalyze the hydro1ysis Of starch, but in different ways (cf' P' of fungal amylase is lower (75°C) than that of 67). beta-amylase but generally only a small amount of alpha-amylase. The amount of alpha-amylase, however, increases considerably when wheat germinates. Indeed, flour from wheat containing amylase activity, with the result that, during bak￾ing, some of the starch is changed into dextrin-like substances. Water-holding capacity is reduced, the crumb is weakened, and the dextrins make the crumb sticky (cf. p. 67). However, flour with too high a natural alpha-amylase activity could be used for making satisfactory bread by microwave or radio-frequency baking methods (cf. p. 206). Another possibility would be to make use of an alpha-amylase inhibitor, e.g. one prepared from barley, as described in Canadian Patent No. 1206157 of 1987 (Zawistowska et al., 1988). The functions of starch in the baking of bread are to dilute the gluten to a desirable consistency, to provide sugar through diastasis, to provide a strong union with gluten, and by gelatinization to become flexib1e and to take water from the set and become rigid. Norma1 flour from sound wheat contains amp1e formation of gummy dextrins during baking and many 'prouted grains may have too high an alpha- allow the loaf to rise, must yet be strong enough gluten, a process which he1ps the gluten fi1m to bonds, including disulphide (-SS-) bonds, and Gas production and gas retention The creation of bubble structure in the dough is a fundamental requirement in breadmaking. The carbon dioxide generated by yeast activity does not create bubbles: it can only inflate gas cells already formed by the incorporation of air during mixing. Adequate gas must be produced during fermen￾tation, otherwise the loaf will not be inflated suf￾ficiently. Gas production depends on the quantity of soluble sugars in the flour, and on its diastatic power. Inadequate gassing (maltose value less than 1.5) may be due to an insufficiency of damaged starch or to a lack of alpha-amylase; the latter can be corrected by adding sprouted wheat to the grist, or malt flour, or fungal amylase, e.g