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The mysteries of baking bread

15 April 2000

Although we have been making bread for almost 7,000 years, no-one really understands how the process works. So scientists at the Institute of Food Research on the Norwich Research Park are unravelling the mysteries of dough. Their work will help reduce wastage and the use of additives in the bakery industry, as well as improving the bread-making quality of flour.

Baking is not an exact science. A major problem faced by the bread-making industry is that the quality of different batches of flour can only be judged by using them to bake a loaf. Variability between flour batches can lead to costly wastage. This is a particular problem with European wheat, where the changeable climate can affect the bread-making properties of the flour.

Another problem is that dough in a loaf tin can collapse if the tin is knocked or banged before cooking - something that often happens in an industrial bakery. So additives are included in the dough to stabilise it and prevent it from collapsing. One of the goals of the IFR scientists is to help reduce the need for these additives. To do this, they are trying to understand how the various components of the dough behave and interact with each other.

The main ingredient of bread dough is flour. This is mostly starch, but also contains proteins, known as gluten. We know that the gluten is crucial for bread-making quality, as it helps make the dough stretchy and elastic.

On the small scale, dough is mixed and must then be kneaded. The physical and biological changes caused by kneading are not fully understood, but they seem to make the dough more elastic. Air also seems to be crucial to the process. If the dough is kneaded in an atmosphere containing, say, nitrogen instead of air, the resulting loaf is of poorer quality.

Bread-making (along with wine and cheese-making) is one of the oldest examples of 'biotechnology' - where biological processes are harnessed to help make useful products. In baking, yeast is added to the dough and produces a gas - carbon dioxide, which makes the loaf rise.

Leaving the dough to 'prove' allows the gas bubbles produced by the yeast to expand. So bread dough is really just a 'foam'? - a collection of bubbles. This is where the gluten plays a crucial role. If the gluten is too strong, the loaf won't rise, as the gas bubbles can't form properly in the dough. But if the gluten isn?t strong enough, the bubbles become too large and the loaf ends up with a hole in the middle. The dough is then cooked in a hot oven, where the foam sets. This traps the gas bubbles within the loaf.

On an industrial scale, the process is quicker than in our kitchens at home, but the general principles (and problems) still apply.

The type and amount of the essential proteins in the flour varies depending on the environmental conditions in which the wheat was grown. So another goal is a better understanding of different environmental effects on the bread-making qualities of wheat flour. The hope is that as well as helping improve the baking process, this work could also lead to better advice for growing practice for farmers.

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