Dried gluten
The addition of dried gluten to flours to improve their quality for bread-making purposes is relatively common (Cauvain, 2007c). Dried, vital
gluten consists mainly of the water-soluble proteins extracted from flour derived from a shortened milling process. The addition of dried gluten to flours improves their gas retention properties, though the degree to which they are improved depends on the composition of the gluten (mainly its protein content) and the effects of processing (especially drying) on its functionality (vitality). The water absorption capacity of dried gluten is greater than that of wheat flour, weight for weight, and usually it is necessary to increase the addition of water in a dough to which dried gluten has been added by approximately one and a half times the weight of added dry gluten. Where the flour used in bread-making already contains dried gluten before it arrives in the bakery, the water absorption capacity of the blend can be determined by any of the normal methods described above.
It is important that the dried gluten is rehydrated during dough mix-ing so that it can confer functionality to the dough. Rehydration is not usually a problem in mixing, even in the CBP (Cauvain and Young, 2006), and it is not normally necessary to prehydrate the dried gluten before mixing, provided it is in the form of a fine powder. Rarely, unhydrated gluten particles may be seen as small white spots on product crusts.
Salt
Common salt or sodium chloride is added to most fermented products and strongly affects bread flavour (Cauvain, 2007d). Sodium chloride is composed of sodium and chlorine ions (NaCl= Na+ + CI−) and dissociates fully in water. The overall effect of increasing salt additions is to decrease the water absorption of the flour as measured with the Farinograph (Linko et al., 1984).
Another effect of adding salt is to lower the water activity of the solution (see Chapter 6), which decreases the availability of water for other reactions. The strong affinity that salt has for water forms the basis of salting to preserve meats and protect them from microbial spoilage (Honikel, 1989). In breadmaking, the rate of yeast fermentation is related directly to the salt level in the dough (Williams and Pullen, 2007). This occurs because of the reduced water availability and because of the effect on the osmotic process of the yeast cells. Direct contact between yeast cells and salt should be avoided; otherwise the integrity of the cell wall can be compromised and yeast activity seriously impaired.
In addition to affecting the activity of microorganisms, the addition of salt makes water less available for the hydration and gluten develop-ment processes that take place in bread doughs. In general, the overall effect is small compared with the development that comes from the en-ergy transferred to the dough during mixing. With slower speed mixers, the overall transfer of energy to the dough is relatively small during
mixing and so the effect of salt on dough development is greater and a ‘delayed-salt’ mixing process may be employed with slower speed mixers. This consists of delaying the addition of the salt until the dough has been formed and mostly developed. Because salt is readily soluble, there should be no specific problems with its dispersion and dissolution provided sufficient additional mixing time is allowed.
In the UK there have been recent moves to reduce the salt content of breads though this has not been without some concerns being expressed (Anon, 2005). The impact on lower salt levels in a bread dough may result in a need to make slight reductions in added water levels to compensate for a slight increase in dough stickiness (Cauvain, 2007d). Such changes may well be associated with changes in the underlying development of the gluten structure because of changes in the competition for water during dough mixing as discussed above.
Sugars
Sucrose and other sugars are often added to bread doughs to produce a sweeter flavour, increase crust browning, and in some cases to support yeast fermentation. Sugar additions produce doughs that are softer, and therefore may require a reduction in the added water level in order to maintain dough consistency. Like salt, the addition of sugars lowers the water activity of the dough (see Chapter 6); this has the effect of inhibiting gluten formation during mixing.
Enzymes
Enzymes need to have sufficient water available for them to be able to exert their various effects. In bread doughs, there is almost always suf-ficient water present to at least initiate the actions of enzymes during mixing, even if their effects on dough are not manifest until later in the process (e.g. the effects of alpha-amylase during baking, see Chapter 4).
However, if sufficient enzymic action occurs during doughmaking, this usually leads to a softening of the dough which requires a compensatory reduction in added water levels in order to maintain an optimum dough consistency. Changes in dough rheology are also known resulting from the addition of hemicellulases (zylanase) and lipase. The precise change depends on the source of the enzyme and the level at which it is being added but commonly high levels of enzyme addition require a compen-satory decrease in added water level to deliver the dough which can be processed without problems. Not all enzyme additions result in dough softening; for example Gerrard et al. (1998) found that transglutaminase substantially improved dough water absorption, along with improved crumb strength and reduced work input.
Non-wheat fibres
In many parts of the world the consumer trend is a decreased consump-tion of white bread and an increased consumpconsump-tion of whole, brown and breads with added fibres. A driver for such a change is the increasing awareness of the value of fibre in the diet and the potential benefits for sectors of the population in the consumption of breads with a low gly-caemic index or glygly-caemic load. A range of fibre products may be added to satisfy the dietary requirements of consumers. They include wheat bran and germ in wholemeal and bran- and germ-enriched breads and fibres from a range of cereals (e.g. Vitacelroat and wheat fibre; Bollinger, 2005), seed, fruit and vegetable sources. Recently the range of materials has extended to include sources of ‘resistant starch’, such as Hi-MaizeTM, a high-amylose maize starch product (www.nationalstarch.com).
Whatever the source of the fibre, its use in bread and fermented doughs will require the addition of extra water in order to maintain a standard dough consistency. The level of additional water required will increase as the level of fibre addition increases and the absolute level of addition will vary with type of fibre. One of the potential problems with fibre additions to the bread dough is that it may take some while for the fibre to fully absorb the additional water and so the rheological properties of the dough will vary from the start to finish of processing.
Usually the dough becomes stiffer with increasing processing time as the fibres hydrate and this may cause problems with dough moulding (see below). Bread and fermented dough made with high level of fibres may benefit from a pre-hydration phase before the main mixing stage as discussed above (Katina, 2003).
Other ingredients
A number of ingredients become effective during dough mixing when they go into solution, including:
r
Ascorbic acid, which acts as an oxidising agent and improves dough development (Williams and Pullen, 2007).r
L-Cysteine hydrochloride, which acts as a reducing agent and modifies dough rheology (Williams and Pullen, 2007). Usually there is a soft-ening of the dough which may require a small reduction in the added water level.r
Calcium phosphates, which have been used in frozen dough production to increase dough firmness through gluten interaction and water-binding effects (Anon, 1994/1995).Some ingredients need to become hydrated in order to confer their spe-cial properties to bread products; they include milk powders, which
affect product colour and flavour, although these have limited use in breads. The use of milk powders affects the water absorption capacity of the dough and added water levels should be increased by approxi-mately the same weight of milk powders used.
Other ingredients may affect the level of water which is added to the dough to meet a specified consistency; they include:
r
Soya flour, which is used to whiten bread colour and improve dough oxidation (Williams and Pullen, 2007). The addition of soya flour requires an increase in added water levels of about half the soya weight used.r
Gums and starches, which may be used to make some specialised fermented products. Added water levels are usually increased in proportion to the added ingredient weight.r
Other grains, which are used in multigrain breads to add special tex-tural characteristics, eating qualities and flavours (Cauvain, 2007b).They may be added in the whole, cracked or kibbled form, and will all affect the water absorption capacity in the dough to greater or lesser degrees. In some cases water will be absorbed slowly during post-mixing processes, and this makes it difficult to adjust water levels to provide an optimum dough consistency for moulding (as discussed above).