Sourdough starter, popularly known as "The Mother Sponge" is also referred to as 'chief' or 'head'. 'Chef' is a French term assigned to a sourdough starter involved in the making a fresh batch of bread. Basically it is a blend of yeast culture, flour and water. However, in sweet-tasting sourdough breads sugar and milk are added as extra ingredients to the sourdough starter.
It is essentially a small portion of dough derived from an earlier lot during bread making that can be used in the next batch to provide similar characteristics as desired. Hence it wouldn’t be wrong to refer to it as ‘mother dough.’ Since the starter has high levels of yeasts and lactobacilli working to complement each other, it acts as an inoculant to start the activity of these micro-organisms in the freshly prepared dough. The presence of lactobacilli culture in any dough makes its properties identical to a sourdough. Thus mother dough often refers to a sourdough starter. Since a sourdough also has both yeasts and lactobacillus in a synergetic combination, it is considered one of the primary means of biological leavening. In certain varieties of breads, like rye-based breads the use of only yeast does not yield best results, rather a combination as present in the chef acts an ideal starter for the final bread. Lactic acid synthesized by the lactobacilli lends a characteristic sour taste and tangy flavour that is relished by people who opt for these types of bread.
The use of such a fermentation starter in the bread-making process has additional benefits. A longer fermentation time allows longer time for the yeast, bacterial and enzymatic actions to take place on the starch and proteins present in the flour. This has multiple effects – improved keeping time of the particular bread after it is baked, enhanced intricate flavours. Artisan Bread making and some other traditional methods still employ the use of chef today, while most commercial bread making directly use yeast for simplifying the process.
Sometimes it is possible through detailed study and using accurate scientific steps to develop a culture with optimal ratios of the microorganisms in defined quantities in order to be able to manufacture particular bread styles. Mostly though in a traditionally obtained starter, it may not be possible to estimate precise micro-organism ratios.
A fresh culture for can be prepared using the common ingredients involved in baking i.e flour and water. As such, fresh flour naturally houses within itself has numerous yeasts and even bacterial spores. With the addition of water, naturally occurring amylase enzymes, disintegrate the starch into disaccharides like maltose. This maltose in turn gets converted into glucose by the action of enzyme maltase. Glucose thus produced, feeds the yeasts. Unwashed organic grape skins may sometimes be used to seed the reaction as they form a source of both yeasts as well as lactic acid bacteria.
Depending on its water content, approximately 20-25 % of chef is added to the dough; it is kneaded well and allowed to rest so that it rises in the usual manner.
There is usually no fear of external contamination in a chef and it remains stable for several days owing to the acidic levels created by inherent microorganisms present. The main upside of sourdough starter is that when regularly fed with flour and water it can be preserved healthy and usable for an indefinite period of time even at room temperature. Hence, dont be surprised if the baker claims that his sourdough starter has years of history.