8 Bread-baking Technology Principles of baking of discrete and separate particles, but the Primitive man, a nomadic hunter and gathe gluten is cohesive, forming a continuous three- erer of fruits and nuts started to settle down and dimensional structure which binds the four abandon his nomadic life when, in Neolithic particles together in dough. The gluten times he discovered how to sow the seeds of has peculiar extensible properties: it can be grasses and, in due time, reap a crop of 'cereal stretched like elastic, and possesses a degree grains. With this change in his way of life came of recoil or spring the beginnings of civilization which, in western air bubbles are folded into the dough. During Europe, is based on a diet relying on wheat, the subsequent handling of the dough these wheaten four, and the baked products made from bubbles divide or coalesce. Eventually the flour, the principal product being bread dough comes to resemble a foam, with the The function of baking is to present cereal bubbles trapped in the gluten network; fours in an attractive, palatable and digestible enzymes in the yeast start to ferment the sugars present in the flour and, later, the While wheat is the principal cereal used for sugars released by diastatic action of the breadmaking, other cereals, particularly rye, are amylases on damaged starch in the also used to some extent. The first part of this breaking them down to alcohol and chapter will consider breadmaking processes and dioxide. The carbon dioxide gas mixes with bread in which wheat four or meal is the sole the air in the bubbles and brings about expan cereal. The use of other cereals will be discussed ion of the dough. " Bread is fundamentally later(p. 211). foamed gluten"(Atkins, 1971) Three requirements in making bread from Use of milled wheat products for brea wheat flour are formation of a gluten network Bread is made by baking a dough which ha and the creation of air bubbles within it: the for its main ingredients wheaten flour, water incorporation of carbon dioxide to turn the gluten yeast and salt. Other ingredients which may be rheological properties of the gluten so that it added include fours of other cereals, fat malt flour, soya flour, yeast foods, emulsifiers, mill retains the carbon dioxide while allowing expan and milk products, fruit, gluten sion of the dough; and, finally, the coagulation of the material by heating it in the oven so that When these ingredients are mixed in correct the structure of the material is stabilized.The proportions, three processes commence advantage of having an aerated, finely vesiculated the protein in the four begins to hydrate, i. e. crumb in the baked product is that it is easily to combine with some of the water, to form masticated gluten(cf. pp. 70 and 174). Flour Corresponding with these requirements, there
8 Bread- ba ki ng Tech nology Principles of baking Primitive man, a nomadic hunter and gatherer of fruits and nuts, started to settle down and abandon his nomadic life when, in Neolithic times, he discovered how to sow the seeds of grasses and, in due time, reap a crop of ‘cereal grains’. With this change in his way of life came the beginnings of civilization which, in western Europe, is based on a diet relying on wheat, wheaten flour, and the baked products made from flour, the principal product being bread. The function of baking is to present cereal flours in an attractive, palatable and digestible form. While wheat is the principal cereal used for breadmaking, other cereals, particularly rye, are also used to some extent. The first part of this chapter will consider breadmaking processes and bread in which wheat flour or meal is the sole cereal. The use of other cereals will be discussed later (p. 211). Use of milled wheat products for bread Bread is made by baking a dough which has for its main ingredients wheaten flour, water, of discrete and separate particles, but the gluten is cohesive, forming a continuous threedimensional structure which binds the flour particles together in a ‘dough’. The gluten has peculiar extensible properties: it can be stretched like elastic, and possesses a degree of recoil or spring; - air bubbles are folded into the dough. During the subsequent handling of the dough these bubbles divide or coalesce. Eventually the dough comes to resemble a foam, with the bubbles trapped in the gluten network; - enzymes in the yeast start to ferment the sugars present in the flour and, later, the sugars released by diastatic action of the amylases on damaged starch in the flour, breaking them down to alcohol and carbon dioxide. The carbon dioxide gas mixes with the air in the bubbles and brings about expansion of the dough. “Bread is fundamentally foamed gluten” (Atkins, 1971). Three requirements in making bread from wheat flour are formation of a gluten network and the creation of air bubbles within it; the incorporation of carbon dioxide to turn the gluten network into a foam; and the development of the yeast and sa1t* Other ingredients which may be added inc1ude flours Of Other cerea1sY fat, ma1t rheological properties of the gluten so that it retains the carbon dioxide while allowing expan- flour, soya flour, yeast foods, emulsifiers, milk and milk products, fruit, gluten. When these ingredients are mixed in correct proportions, three processes commence: - the protein in the flour begins to hydrate, i.e. to combine with some of the water, to form gluten (cf. pp. 70 and 174). Flour consists sion of the dough; and, finally, the coagulation of the material by heating it in the oven so that the structure of the material is stabilized. The advantage of having an aerated, finely vesiculated crumb in the baked product is that it is easily masticated. Corresponding with these requirements, there 191
TECHNOLOGY OF CEREALS are three stages in the manufacture of bread than about 14% to permit safe storage, and xing and dough development, dough aeration satisfactory colour, and should meet specifica- and oven baking. The method of dough develop. tions regarding bleach and treatment ment and aeration that has been customary since pp.171-172) the time of the Pharaohs is panary fermentation by means of yeast These requirements are met by the type of heat called' trong’(cf.pp.81,92,174),ⅵiz wheat having a reasonably high protein content Ingredients Wherever possible, home-grown wheat is used for breadmaking, and this is the situation, for In the U. K, however, the home-grown wheat protein which is adequate in quantity and is, or until recently was, characteristically weak which, when hydrated, yields gluten which is viz, of low protein content, and would not, by satisfactory in respect of elasticity, strength itself, yield four from which bread, of the kind and stability to which u.K. consumers are accustomed. could satisfactory gassing properties: the levels of be made. It was therefore customary for flour amylase activity and of damaged starch (cf. millers in the U. K. to mill breadmaking flour pp. 183, 185) should be adequate to yield from a mixed grist of strong and weak wheats sufficient sugars, through diastatic action, to the strong wheat component being imported support the activity of the yeast enzymes generally from Canada, and the weak component during fermentation and proof; being home-grown U. K. wheat. Until the early satisfactory moisture content - not higher 1960s, the average breadmaking grist in the U. K Composition of bread wheat grist in U. K U.K %40 i other EC 讠b %%影 PIG& EC wereage compe ion of the bread wheat grist in the U. K. since 1973, in terms of U. K. wl n-EC wheat(data from MAFF, H-GCA, and NABIM
192 TECHNOLOGY OF CEREALS are three stages in the manufacture of bread: mixing and dough development, dough aeration, and oven baking. The method of dough development and aeration that has been customary since the time of the Pharaohs is panary fermentation by means of yeast. Ingredients Flour Good breadmaking flour is characterized as having: - protein which is adequate in quantity and which, when hydrated, yields gluten which is satisfactory in respect of elasticity, strength and stability; - satisfactory gassing properties: the levels of amylase activity and of damaged starch (cf. pp. 183, 185) should be adequate to yield sufficient sugars, through diastatic action, to support the activity of the yeast enzymes during fermentation and proof; - satisfactory moisture content - not higher than about 14% to permit safe storage, and satisfactory colour, and should meet specifications regarding bleach and treatment (cf. pp. 171-172). These requirements are met by the type of wheat called ‘strong’ (cf. pp. 81, 92, 174), viz. wheat having a reasonably high protein content. Wherever possible, home-grown wheat is used for breadmaking, and this is the situation, for example, in Canada and in the U.S.A., where such strong wheats, e.g. CWRS, HRS, are readily available. In the U.K., however, the home-grown wheat is, or until recently was, characteristically weak, viz. of low protein content, and would not, by itself, yield flour from which bread, of the kind to which U.K. consumers are accustomed, could be made. It was therefore customary for flour millers in the U.K. to mill breadmaking flour from a mixed grist of strong and weak wheats, the strong wheat component being imported, generally from Canada, and the weak component being home-grown U.K. wheat. Until the early 1960s, the average breadmaking grist in the U.K. Composition of bread wheat grist in U K 80 - 70 - YO 40- 10 - I A I I I I I I I 1w-i-r I I I I I I AAAAAAJ@@@@@@@@@% ~~~~~~~:L+-~ 9_gt+ EPJ\@-\@&lG&’+V\Pdd-\@&l9, ‘\ O Year FIG 8.1 Average composition of the bread wheat grist in the U.K. since 1973, in terms of U.K. wheat, other EC wheat, and non-EC wheat (data from MAFF, H-GCA, and NABIM)
BREAD-BAKING TECHNOLOG 193 would consist of 60-70% of imported strong wheat in the U. K. bread -wheat grist has fallen from plus 20-30% of weak home-grown wheat(with a about 70%in 1960 to about 15% in 1990(with a small proportion of filler'wheat of medium corresponding increase in the home-grown whea strength, cf. p. 87)-see Fig 8. 1, yielding a white proportion), with a considerable saving in the cost four of about 12% protein content of the raw material. By 1992, some millers were The imported Canadian wheat is more expen- supplying breadmaking four milled entirely from sive than the home-grown U. K. wheat and, in home-grown U. K. and ec wheats, with no non- consequence, there was a strong urge to decrease EC component, but with the addition of 2% or the ratio of strong to weak wheat. This change perhaps 2.5% of vital gluten was made possible in a number of ways, one of A similar reduction in the imported non-EC which was the advent of the CBP(cf. p. 203)(strong)wheat content of the breadmaking grist because, among other advantages, the cBp per- has also occurred in other countries mitted the use of a flour of about 1% lower protein One possible complication associated with the content to produce bread of quality equivalent to lowering of the strong/weak wheat ratio in the hat produced by the bFP(cf. p 201) bread grist is the reduced proportion of damaged Additional impetus to reduce still further the starch in the flour because of the frequent associa- proportion of imported strong wheat in the bread tion of strength with hardness(as in the importe grist followed the entry of the U. K into the EC, Canadian wheat)and, conversely, of weakness and the imposition of a heavy import levy, which with softness(as in the EC-grown wheats). It has run as high as f120-130 per tonne, on the desirable that the content of damaged starch cost of wheat imported from third (i.e. non-EC) should be maintained at a reasonably high level countries. Various measures have been adopted and this requirement can be met by adjustments whereby the proportion of home-grown (or EC- to the milling process (cf p. 149). However, it is grown) wheat in the breadmaking grist could be a fortunate coincidence that the two varieties of further increased, while maintaining loaf quality. wheat classified by breadmaking quality and They include: widely grown in the U. K. at the present time, breeding stronger wheats with higher yielding Avalon and mercia, both have a hard texture endosperm, and thus go some way towards potential for growing in the U.K. and other avoiding this complication EC countries. Examples of such promising new varieties are Avalon and Mercia. More- over the considerable increase in the size of the U. K. wheat harvest in recent years has Leavening provided the Aourmiller with the possibility Leavened baked goods are preferred in all of obtaining adequate supplies of these newer countries where wheat is available as a staple food varieties of good breadmaking quality Leavening can be achieved in several ways, awarding of remunerative premiums to growers including the following are poorer yielders than low protein wheats; I. Whisking egg into a foam with four and other of vital gluten as a bread ingredient(cf p.195 tion of sponge and other cakes supplementation of flours from lower-protein 2. Water vapour production as in Scandinavian home-grown wheats with air-classified high fat breads and puff pastry protein fractions of four(cf. p. 132); 3. Yeast use of high levels of fungal alpha-amylase(cf. 4. Baking powder p.196) Yeast and baking powder are the most import Figure 8. 1 shows that the proportion of imported ant. Each is appropriate for its own range of non-EC wheat(mostly Canadian CWRS wheat) products, and in some cases, such as doughnuts
BREAD-BAKING TECHNOLOGY 193 would consist of 60-70% of imported strong wheat in the U.K. bread-wheat grist has fallen from plus 20-30% of weak home-grown wheat (with a about 70% in 1960 to about 15% in 1990 (with a small proportion of ‘filler’ wheat of medium corresponding increase in the home-grown wheat strength, cf. p. 87) - see Fig. 8.1, yielding a white proportion), with a considerable saving in the cost flour of about 12% protein content. of the raw material. By 1992, some millers were The imported Canadian wheat is more expen- supplying breadmaking flour milled entirely from sive than the home-grown U.K. wheat and, in home-grown U.K. and EC wheats, with no nonconsequence, there was a strong urge to decrease EC component, but with the addition of 2% or the ratio of strong to weak wheat. This change perhaps 2.5% of vital gluten. was made possible in a number of ways, one of A similar reduction in the imported non-EC which was the advent of the CBP (cf. p. 203) (strong) wheat content of the breadmaking grist because, among other advantages, the CBP per- has also occurred in other countries. mitted the use of a flour of about 1% lower protein One possible complication associated with the content to produce bread of quality equivalent to lowering of the strong/weak wheat ratio in the that produced by the BFP (cf. p. 201). bread grist is the reduced proportion of damaged Additional impetus to reduce still further the starch in the flour because of the frequent associaproportion of imported strong wheat in the bread tion of strength with hardness (as in the imported grist followed the entry of the U.K. into the EC, Canadian wheat) and, conversely, of weakness and the imposition of a heavy import levy, which with softness (as in the EC-grown wheats). It is has run as high as &120-130 per tonne, on the desirable that the content of damaged starch cost of wheat imported from third (Le. non-EC) should be maintained at a reasonably high level, countries. Various measures have been adopted and this requirement can be met by adjustments whereby the proportion of home-grown (or EC- to the milling process (cf. p. 149). However, it is grown) wheat in the breadmaking grist could be a fortunate coincidence that the two varieties of further increased, while maintaining loaf quality. wheat classified by breadmaking quality and They include: widely grown in the U.K. at the present time, Avalon and Mercia, both have a hard textured - breeding stronger wheats with higher yielding endosperm, and thus go some way towards potential for growing in the U.K. and other avoiding this complication. EC countries. Examples of such promising new varieties are Avalon and Mercia. Moreover, the considerable increase in the size of Leavening the U.R. wheat harvest in recent years has provided the flourmiller with the possibility Leavened baked goods are preferred in all of obtaining adequate supplies of these newer countries where wheat is available as a staple food. varieties of good breadmaking quality; Leavening can be achieved in several ways, - awarding of remunerative premiums to growers including the following: for higher protein home-grown wheats which are poorer yielders than low protein wheats; - use of vital gluten as a bread ingredient (cf. p. 195); - supplementation of flours from lower-protein home-grown wheats with air-classified high protein fractions of flour (cf. p. 132); - use of high levels of fungal alpha-amylase (cf. p. 196). Figure 8.1 shows that the proportion of imported non-EC wheat (mostly Canadian CWRS wheat) 1. Whisking egg into a foam with flour and other ingredients. This method is used in production of sponge and other cakes. 2. Water vapour production as in Scandinavian flat breads and puff pastry. 3. Yeast. 4. Baking Powder. Yeast and baking powder are the most important. Each is appropriate for its own range of products, and in some cases, such as doughnuts
194 TECHNOLOGY OF CEREALS coffee cake, and pizza-dough, either may be used of one strain to the genome of another. Strains alone or in combination that have an excellent performance in sugar-rich doughs normally show a poor performance in Baking powders lean doughs, but the subject of a European Patent EP0 306 107 A2) is a yeast that performs well Baking powders depend upon sodium bicarbon- both in high sucrose conditions and also in ' lean ate as a source of co z gas, which may be liberated conditions, where maltose is the available sub- by the action of sodium acid phosphate, mono- strate. The technique involved was the introduc- calcium phosphate, sodium aluminium phos- tion of genes coding for increased activity of the phate or glucono-8-lactone. One hundred grams two enzymes maltose permease and maltase(alpha- f baking powder generates 15 mg (or 340 mM, glucosidase), allowing best use to be made of the or 8.2 D of COz. Some is released at dough limited quantities of maltose available in a lean temperature and the remainder during baking Ability to ferment sugars anaerobically remains Yeast the major criterion of selection, but meeting this under different conditions has led to the introduc The quantity of yeast used is related inversely tion of specialized strains. The conditions that to the duration of fermentation, longer fermenta- provide the challenge include the requirements tion systems generally employing somewhat lower (a) to be supplied and stored in a dry form with levels of yeast and also lower dough temperatures. a longer life than the traditional compressed form Thus, 1% of yeast on four wt would be used for (b)to retain high activity in high sugar formula- a 3 h straight dough system with the dough at tions and (c) to retain activity in yeast-leavened 27C, whereas 2-3%of yeast on flour wt would be frozen doughs required for a no-time dough at 27-30.C. Yeast activity increases rapidly with temperature, and its level of use is therefore reduced if the temper Dried yeasts ature is increased within a fixed tir Until the early 1970s, two strains of Saccharo- In addition to providing CO2 as a leavening myces cerivisiae were used widely. The yeast was agent, yeast also affects rheological properties of grown to a nitrogen level of 8 2-8.8%(on a dry dough through the lowering of ph by CO2 basis), and an A DY.(active dry yeast), which ical effects of bubble expansion. Further, yeast in the pelleted product, it had only 75-80% of ontributes significantly to the flavour and aroma the gassing activity of the compressed yeasts of baked products (when compared on the same m.c. basis). New Yeast is used in several different forms: com- products available since that time have allowed pressed, cream (liquid), dried into pellets, and the gap to be narrowed, although it does still exist instant active powders Three forms of dried yeast are now available In recent years, attitudes to yeast production A D.Y., and the pot have become more enterprizing Specialized strains A D.Y. (I.A. D P powdered products Instant and protected A.D.Y. have been selected and bred to meet newly identi- (P.A. .Y fied criteria. This has resulted partly from changing A D.Y. must be rehydrated in warm water technologies within the baking industries and (35%-40oC)before it is added to dough, while partly from new means of genetic manipulation. I A D.Y. and P A D.Y. can be added to dry Examples of these innovations are the replace- ingredients before mixing. In fact, this results in ment of conventional spore fusion by protoplast more productive gassing. During storage, dried fusion, and genetic engineering through the use yeasts are subject to loss of activity in oxygen of recombinant DNA(rDNA)for introduction The improved strains are supplied in vacuum of an advantageous segment of the genetic materials packs or in packs with inert gas in the headspace
194 TECHNOLOGY OF CEREALS coffee cake, and pizza-dough, either may be used of one strain to the genome of another. Strains alone or in combination. that have an excellent performance in sugar-rich doughs normally show a poor performance in lean doughs, but the subject of a European Patent (El' 0 306 107 A2) is a yeast that performs well Baking powders Baking powders depend upon sodium bicarbon- both in high sucrose conditions and also in 'lean' ate as a source of C02 gas, which may be liberated conditions, where maltose is the available subby the action of sodium acid phosphate, mono- strate. The technique involved was the introduccalcium phosphate, sodium aluminium phos- tion of genes coding for increased activity of the phate or glucono-&lactone. One hundred grams two enzymes maltose permease and maltase (alphaof baking powder generates 15 mg (or 340 mM, glucosidase), allowing best use to be made of the or 8.2 1) of C02. Some is released at dough limited quantities of maltose available in a lean temperature and the remainder during baking. dough. Ability to ferment sugars anaerobically remains the major criterion of selection, but meeting this under different conditions has led to the introduc- Yeast The quantity of yeast used is related inversely tion of specialized strains. The conditions that to the duration of fermentation, longer fermenta- provide the challenge include the requirements: tion systems generally employing somewhat lower (a) to be supplied and stored in a dry form with levels of yeast and also lower dough temperatures. a longer life than the traditional compressed form; Thus, 1% of yeast on flour wt would be used for (b) to retain high activity in high sugar formulaa 3 h straight dough system with the dough at tions and (c) to retain activity in yeast-leavened 27"C, whereas 2-3% of yeast on flour wt would be frozen doughs. required for a no-time dough at 27"-3OoC. Yeast Dried yeasts activity increases rapidly with temperature, and its level of use is therefore reduced if the temperature is increased within a fixed time process. Until the early 1970s, two strains of SaccharoIn addition to providing C02 as a leavening myces cerivisiae were used widely. The yeast was agent, yeast also affects rheological properties of grown to a nitrogen level of 8.2-8.8% (on a dry dough through the lowering of pH by C02 basis), and an A.D.Y. (active dry yeast), which production, evolution of alcohol, and the mechan- was grown to a nitrogen content of 7.0%. Thus, ical effects of bubble expansion. Further, yeast in the pelleted product, it had only 75-80% of contributes significantly to the flavour and aroma the gassing activity of the compressed yeasts of baked products. (when compared on the same m.c. basis). New Yeast is used in several different forms: com- products available since that time have allowed pressed, cream (liquid), dried into pellets, and the gap to be narrowed, although it does still exist. instant active powders. Three forms of dried yeast are now available: In recent years, attitudes to yeast production A.D.Y., and the powdered products Instant have become more enterprizing. Specialized strains A.D.Y. (I.A.D.Y.) and protected A.D.Y. have been selected and bred to meet newly identi- (P.A.D.Y.). fied criteria. This has resulted partly from changing A.D.Y. must be rehydrated in warm water technologies within the baking industries and (35"40"C) before it is added to dough, while partly from new means of genetic manipulation. I.A.D.Y. and P.A.D.Y. can be added to dry Examples of these innovations are the replace- ingredients before mixing. In fact, this results in ment of conventional spore fusion by protoplast more productive gassing. During storage, dried fusion, and genetic engineering through the use yeasts are subject to loss of activity in oxygen. of recombinant DNA (rDNA) for introduction The improved strains are supplied in vacuum of an advantageous segment of the genetic materials packs or in packs with inert gas in the headspace
BREAD-BAKING TECHNOLOGY (I A D.Y., or in the presence of an antioxi the bread soft and palatable for a longer period (P.A. D.Y. .PA D.Y. features in complete which is equivalent to an anti-staling effect containing flour and other ingredients but the (Hoseney, 1986) four present must be at a very low m c to avoid During storage of flour, free fatty acids accumu- moisture transfer and reduction in the level of late owing to the breakdown of the natural fats production against oxidation and the gluten formed from the protein becomes less soluble and shorter in character. When flour High sugar yeast that has been stored for a long time, e. g. a year, at ambient temperature is used for the CBP, the Products such as Danish pastries, doughnuts fat level should be increased to about 1.5%on nd sweet buns have a high sugar content. The flour wt high osmotic pressures involved are not tolerated by standard yeast strains, but good strains are available as I.A. D.Y. products. Japanese com- Sugar pressed yeasts can also withstand high osmotic Sugar is generally added to bread made in the conditions U.S.A. giving an acceptable sweet favour, but Frozen dough yeasts However, sugar may be included in prover mixes The production of breads from frozen doughs at the point of sale, has increased dramatically Vital gluten and has created a requirement for cryoresistant Vital wheat gluten, viz. gluten prepared in such yeasts. Most yeasts withstand freezing, but way that it retains its ability to absorb water deteriorate rapidly during frozen storage The and form a cohesive mass (cf pp 70, 174), is now best cryoresistant strains perform well in sweet widely used in the U. K. and in other EC countries goods but less well in lean doughs. The require- as an ingredient of bread ment has not been fully satisfied (Reed and Nagodawithana, 1991) at levels of 0.5-3. 0% on flour wt to improve the texture and raise the protein content of bread, crispbread, and speciality breads such as vienna bread and hamburger rolls Salt is added to develop favour. It also toughe to fortify weak flours, and to permit the use ens ne gluten and gives a less sticky dough Salt slows by millers of a wheat grist of lower strong/ down the rate of fermentation and its addition is weak wheat ratio (particularly in the eC sometimes delayed until the dough has been countries) by raising the protein content of partly fermented The quantity used is usually the flour(cf p. 193); 1.8-2. 1%on flour wt, giving a concentration of in starch-reduced high protein breads(cf. p 1.1-1. 4% of salt in the bread. salt is added either 209), in which the gluten acts both as a source as an aqueous solution(brine)or as the dry solid of protein and as a texturing agent in high-fibre breads(cf. p. 209)now being made in the u.s.A. to maintain the texture Fat is an essential ingredient for no-time In the U.S. A about 70%of all vital gluten is doughs, such as the CBP. Added at the rate of used for bread, rolls, buns and yeast-raised goods about 1% on four wt, fat improves loaf volume, (Magnuson, 1985). vital gluten is also used as a reduces crust toughness and gives thinner crumb binder to raise the protein level in meat products cell walls, resulting in a softer-textured loaf with e.g. sausages, and in breakfast cereals(e.g improved slicing characteristics. Fat also keeps Kelloggs Special K), breadings, batter mixes
BREAD-BAKING TECHNOLOGY 195 (I.A.D.Y.), or in the presence of an antioxidant the bread soft and palatable for a longer period, (P.A.D.Y.). P.A.D.Y. features in complete mixes which is equivalent to an anti-staling effect containing flour and other ingredients but the (Hoseney, 1986). flour present must be at a very low m.c. to avoid During storage of flour, free fatty acids accumumoisture transfer and reduction in the level of late owing to the breakdown of the natural fats, production against oxidation. and the gluten formed from the protein becomes less soluble and shorter in character. When flour that has been stored for a long time, e.g. a year, High sugar yeast at ambient temperature is used for the CBP, the Products such as Danish pastries, doughnuts fat level should be increased to about 1.5% on and sweet buns have a high sugar content. The flour wt. high osmotic pressures involved are not tolerated by standard yeast strains, but good strains are Sugar available as I.A.D.Y. products. Japanese compressed yeasts can also withstand high osmotic Sugar is generally added to bread made in the conditions. U.S.A., giving an acceptable sweet flavour, but it is not usually added to bread in the U.K. However, sugar may be included in prover mixes. Frozen dough yeasts The production of breads from frozen doughs, vital gluten at the point of sale, has increased dramatically and has created a requirement for cryoresistant Vital wheat gluten, viz. gluten prepared in such yeasts. Most yeasts withstand freezing, but a way that it retains its ability to absorb water deteriorate rapidly during frozen storage. The and form a cohesive mass (cf. pp. 70,174), is now best cryoresistant strains perform well in sweet widely used in the U.K. and in other EC countries goods but less well in lean doughs. The require- as an ingredient of bread: - at levels of 0.5-3.0% on flour wt to improve ment has not been fully satisfied (Reed and the texture and raise the protein content of Nagodawithana, 199 1). bread, crispbread, and speciality breads such Salt as Vienna bread and hamburger rolls; - to fortify weak flours, and to permit the use by millers of a wheat grist of lower strong/ Salt is added to develop flavour. It also toughens the gluten and gives a less sticky dough. Salt slows weak wheat ratio (particularly in the EC down the rate of fermentation, and its addition is countries) by raising the protein content of the flour (cf. p. 193); sometimes delayed until the dough has been partly fermented. The quantity used is usually - in starch-reduced high protein breads (cf. p. 209), in which the gluten acts both as a source 1.8-2.1% on flour wt, giving a concentration of of protein and as a texturing agent; 1.1-1.4% of salt in the bread. Salt is added either - in high-fibre breads (cf. p. 209) now being as an aqueous solution (brine) or as the dry solid. made in the U.S.A., to maintain the texture Fat and volume. Fat is an essential ingredient for no-time In the U.S.A., about 70% of all vital gluten is doughs, such as the CBP. Added at the rate of used for bread, rolls, buns and yeast-raised goods about 1% on flour wt, fat improves loaf volume, (Magnuson, 1985). Vital gluten is also used as a reduces crust toughness and gives thinner crumb binder to raise the protein level in meat products, cell walls, resulting in a softer-textured loaf with e.g. sausages, and in breakfast cereals (e.g. improved slicing characteristics. Fat also keeps Kelloggs Special K), breadings, batter mixes