Preliminary Doughs

In order to provide a satisfactory account of the principal advances in sourdough production, it is necessary to take a look at the entire system of preparing preliminary doughs and to examine the role of preliminary doughs, in particular sourdoughs, in bread-making. This requires a means of classifying preliminary doughs that takes into account not only their functional properties but also the technological developments that have been put into practice in different geographical regions of the world.

Preliminary doughs can be subdivided into

Sourdoughs: doughs fermented by lactobacilli and sourdough yeasts

Sponges: doughs fermented by yeast

Mashes: mixtures of kernels and/or milled products with hot or cold water

Bread syrups: enzymatically degraded bread crumbs

Liquid ferments: enzymatically degraded fermented mashes containing yeast and/or lactobacilli

Such preliminary doughs are used to different extents in different parts of the world, and for different purposes. For example, sourdoughs, mashes, and bread syrups are widely employed in Germany, whereas sponges, sourdoughs, and liquid ferments are common in America and sourdoughs and liquid ferments are used extensively in Russia (24).

Although production and use of sourdoughs to make different types of baked goods has been known since ancient times this is not true of most other preliminary doughs, in particular their most modern types. These modern preliminary doughs have gained in importance as the production of baked goods has become more mechanized and industrialized. Their development is partly due to mechanization and industrialization, yet it also originated in the diversification of the range of bakery products. As developments in technology and diversification of the range of available bakery products have given rise to new challenges in the production of baked goods, it is necessary to examine briefly the different functional properties of the preliminary doughs and the way in which they affect the quality characteristics of the final products.

Essentially, the role of preliminary doughs in making bread and other bakery products consists not only in improving baking performance, crumb structure, digestibility, and chewiness, but also in delaying crumb staling and prolonging shelf life (6). In addition to this, preliminary doughs, like bread syrups colorized by pressure cooking (25) or mashes soaked in hot water, can be used to determine the color and texture of the crumb. Another important function of preliminary doughs consists in lending the final products a specific flavor. Each preliminary dough fulfils these functions to a limited degree only. Therefore, the selection of a specific preliminary dough depends on that quality criterion of the final product that has to be influenced. A combination of several preliminary doughs may be required for certain bakery products. For example, combinations of sourdoughs, mashes, and bread syrups are used in German wholemeal bread varieties (26).

The specific properties of the preliminary doughs are obtained by means of mechanical, fermentative, enzymic, and thermal process steps. The simplest step involves mixing milled products with water and leaving the mixture to swell for a certain period of time. Swelling can be accelerated by heating the mixture in order to promote reactions of the enzymes present in the raw materials, for example (soaked dough, obtained by soaking coarsely ground grain in warm water). The mixture may also be heated to such a degree that some of the starch is gelatinized (hot soaked dough, obtained by soaking coarsely ground grain in hot water). Incipient gelatinization of the starch is essential if the starch is to be degraded to saccharides (glucose, maltose), which is what happens, for instance, when bread syrup is made by adding amylolytic enzymes. Besides enzymic degradation, it is above all the saccharides of the swollen cereal that can be fermented by metabolic activity of lactic acid bacteria and yeasts and produces either sourdoughs or sponges.

Accordingly, preliminary doughs are produced in accordance with a few basic principles comprising swelling (pentosans, proteins), fermentation (microorganisms, enzymes) and gelatinization (starch), each of which can be adapted in a variety of ways. There is thus wide scope for varying the functional properties of preliminary doughs. This applies in particular to the microbiological production of preliminary doughs.

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