For the past 6000 years or so the vast majority of wheat consumed by humankind has been consumed as leavened bread, and until about 150 years ago all of this bread was produced as sourdough. The technology of the large-scale production of leavened bread is attributed to the Egyptians. The vast bakeries of the pharaohs applied high degrees of divisions of labour, and the use of large numbers of ovens made it possible to reach high production levels. The scale of production is still surprising to us today as a large bakery, capable of producing enough bread to feed more than 15,000 workers per day, was discovered in 1991 within sight of the Great Pyramids.
So it can be realised that bread production relied on the use of sourdough as a leavening agent for most of human history; the use of baker’s yeast as a leavening agent dates back little more than 100 years.
For sourdoughs, optimisation is limited by the laws of microbiology that govern the proliferation of microorganisms and the accompanying metabolic performance. Some say that the longer you have to wait for something, the more you will appreciate its outcome, this is said to be the case for traditional sourdough breads.
These traditional methods of aerating bread dough were based on the use of portions of old dough which had fermented because of the presence of natural, wild yeasts and bacteria.
True Sourdough’s are doughs fermented by lactobacilli and sourdough yeasts and do not rely upon bakers or brewer’s yeast during pre-fermentation.
In English-speaking countries, where wheat-based breads predominate, sourdough is no longer the standard method for bread leavening. It was gradually replaced, first by the use of barm from beer making, then, after the confirmation of germ theory by Louis Pasteur, by cultured yeasts. With the advent of the production of baker’s yeast such traditional baking methods became less popular, in part, because using modern baker’s yeast provided a consistency of gassing performance which could not be readily achieved with ‘natural’ fermentation. However, in some parts of the world and for some products, notably rye breads especially in Germany, then the principles of using starter or ‘mother doughs’ remains in common practice.
Type O – SPONTANEOUS SOURDOUGH – This process involves propagation of the natural flora under optimized media and temperature conditions.
Type I – STARTER DOUGH – this is the traditional method of making sourdough using a starter cultured from just flour and water, which typically contain a diverse range of yeasts and lactic acid bacteria. A portion is kept back and built up / refreshed for the next bake.
Type II – STARTER SPONGE – a more controlled version of the traditional making it adaptable to industrial production. A lower viscosity dough (liquid sponge) is cultured from scratch for each bake using selected bacteria (but not always yeasts), for several days often at a relatively high temperature to generate high acidity. This is mainly used as an acidifier and flavour enhancer and usually always requires commercial yeast to be added as leavening to the final dough.
Type III – READY-TO-USE SOURDOUGH subjected to a drying process, usually either spray or drum drying, and are mainly used at an industrial level as flavouring agents that merely uses dried sourdough powder as an acidifier and flavouring for a short-processed commercially yeasted dough.
The main difference between modern and traditional methods of sourdough production is the viscosity of the dough. Unlike classical high-viscosity sourdoughs, low-viscosity sourdoughs with high dough yields (200%) are able to be pumped, which is a distinct advantage in a commercial bakery. This has paved the way for the continuous production of sourdough and for storing sourdough that is ready for use in both daily and weekly production runs.
Zeppelin Batch Sourdough Production – Type II – STARTER SPONGE
The sourdough production comprises the use of a flour mixture and the sourdough production in a single- or multi-stage preparation. The development of these two kinds of preparation is based on the consideration of a targeted increase of yeast or the generation of a specific acid with aroma. Zeppelin’s batch sourdough system offers this individual system solution. Flour is pneumatically conveyed into a holding hopper and is then metered by an adjustable conveying screw into the fermenter. Parallel to metering of flour, the mixing water is added. A constant comparison of the quantities metered ensures that the desired mixing ratio is observed. As a third raw material the starter is added. Afterwards, homogenous mixing of the raw materials in the fermenter and the hydration of the flour is carried out. The system allows to adjust several preparation stages with variable dough yield and temperature.
After a fermentation time of approx. 12 to 18 hours the finished sourdough can be cooled down in the double-walled fermenter to the desired storage temperature of approx. 15°C. Thus, the sourdough is available for a period of several hours at a constant quality. The double walled and insulated stainless steel tanks fulfil the task of a fermenter and that of a storage tank.
Zeppelin Continuous Sourdough Production – Type II – STARTER SPONGE
Today, sourdough is not only used for rye flour. It is also produced with other types of grain, such as e.g. wheat and spelt in order to use the positive influence of sourdough on the baked goods. In the past and today, sourdough is prepared by a single- or multi-stage process in dough bowls and metered manually, which is a time-consuming and personnel-intensive process. This and the increased quality requirements led to the development of the automatic batch-wise and the continuous production of sourdough – these two processes provide numerous advantages. Which process is the right one for you depends on your requirements. All raw materials are metered continuously. In a vertical mixer, flour, water and starter are homogenously mixed free from lumps. The mixer works according to the rotor-stator-principle. The dough yield is approx. 220 with a sourdough temperature of approx. 30°C. Afterwards, the dough is pumped in the fermentation pipe. The length of the pipe is adapted according to the desired fermentation capacity. The fermentation pipe can also be installed outdoors, e.g. on the roof or on the wall of a building. It serves to ferment the raw materials that were mixed before. When the production process is finished, the complete contents of the fermenter is cooled down to approx. 10°C. Thus the sourdough can be stored over a period of several days and conserved as starter for a new production. Before each new start of the production process, the contents of the pipe is heated up to approx. 30°C. The full sourdough leaves the fermenting pipe with a density of approx. 600 kg/m³. In this pipe, as in each hopper, acetic acid, lactic acid, alcohol and carbon dioxide have developed after a period of 3 hours. Now, the task is to store the sourdough for the production process. It can be pumped and thus, it is directly available for the production. When the storage temperature is too high and a longer resting time is desired, it is possible to cool the sourdough to approx. 10°C.