Cereals processing technology

226 Cereals processing technology
The other contributor to crust formation is the continuing expansion of the
inside of the dough piece from the final burst of carbon dioxide production from
yeast fermentation and the thermal expansion of the gases trapped in the cellular
structure of the dough. If the dough is contained in a pan then it can only expand
upwards. This effect is most obvious at the top edges of the loaf, where the
displacement is greatest and where a split develops as the top crust lifts,
exposing a band of elongated inner crust cells, called the ‘oven break’, ‘oven
spring’ or ‘shred’.
Some types of bread are characterised by the crispness of their crust, e.g.
baguette. The first few moments in the oven are vital for the formation of a
glossy crust. To obtain gloss, it is essential that vapour condenses on the surface
to form a starch paste that will gelatinize, form dextrins and eventually
caramelise to give both colour and shine. If there is excess water, paste-type
gelation takes place while with insufficient water crumb-type gelation occurs.
To deliver the necessary water steam is introduced into the oven.
10.9 Future trends in breadmaking
10.9.1 Ingredients
The trend in the reduction in permitted additives in breadmaking has probably
reached its limits in Europe and many parts of the world. The current exception is
the USA, which still permits a wide range of oxidants, including potassium bromate
and azodicarbonamide which were banned in the UK in 1990 and 1995 respectively.
The trend to limit ‘chemical’ additives has raised the profile of the use of enzyme
active materials as more ‘natural’ additives. While the addition of many enzyme
active materials does improve dough gas retention (Cauvain and Chamberlain,
1988) such materials do not perform the same protein cross-linking function of
oxidising materials. It is likely that the improving effect many enzyme-active
materials contribute to bread quality is related to their ability to change dough
rheology and therefore the influence of the moulding and processing operations.
Recently developed and used enzymes may now be the product of the
fermentation of genetically modified microorganisms or the result of the
fractionation of existing amylase sources. These approaches have developed
bacterial -amylases with heat stability profiles similar to that of fungal -
amylase (Williams and Pullen, 1998). These products give the benefits of
improvement in gas retention while avoiding the problem of excessive dextrin
formation associated with cereal and ‘traditional’ bacterial amylases. In addition
these newer amylases have been shown to have anti-staling properties over
normal bread shelf life. This trend to using more targeted enzymes is likely to
continue in the foreseeable future.
Since a significant proportion of bread quality derives from the wheats that
are used in the milling grist it is certain that greater attention will be paid to
matching wheat/flour quality with end use. This may entail selective breeding or
greater attention to agronomic practices.