It took a while until we are now coming back directly with two new episodes of our little podcast series.

The third episode deals with the work and outcome of work package 3: Fermentation optimisation and process definitions. In this podcast we are talking to Prof. Elke Arend from the University of College Cork.

The objectives of work package 3 are to determine up to 10 processes in order to generate Products with different sensory profiles, to generate data on the fermentation regimes and to determine the quality parameters of bread by the use of several analytical measurements (e.g. Rheofermentometer, Vol-scan Profiler, Texture Profile Analysis, C-Cell Image Analysis). Finally, all collected data was transferred into the process control system.

Elke is talking about the use of yeast for different applications. Yeast is an ubiquitary, unicellular, asexual microorganism which is able to ferment sugars into alcohol and carbon dioxide and therefore is known as the leavening agent in baked goods. It is part of the common environment, mainly on sugar-rich materials (grapes, apples) and the use in the human nutrition and in food products have a very long historical background as it is used since the ancient Egypt.

Long ago in Egypt and the Middle East, both processes, brewing and baking, were closely linked. That remained until the nineteenth century where yeast left over from the breweries was used for bread making. Nowadays, genetically improved microbial cultures are available for commercial use to better suit the need of the operators. Thousands of different Saccharomyces cerevisiae strains in industrial applications, based on the contribution of each strain to consumer and manufacturer desirability. Various S. cerevisiae strains are used for the production of wine, beer and bread. Baker’s yeast ensures uniform dough leavening, good flavour production. Therefore, fermentation as a step in bread making, has a large impact on the improvement of shelf life, texture, taste and flavour of the final product.

Next to different yeast strains this work package deals also with the use of different commercial and non-commercial sour doughs. Sourdough is a mixture of flour and water fermented by lactic acid bacteria (LAB) and yeast. It has very characteristically properties such as acidity, flavour and texture. LAB are part of the normal flora of humans, animals and plants and many species, especially from the genus Lactobacillus. Similar to yeast it is used in the production of fermented foods for millennia and various LAB strains have a range of functional use in food systems. They are especially recognized for their biopreservative properties, because the microflora produces antimicrobial compounds. These are bacteriocins, hydrogen peroxide, organic acids and other low molecular weight compounds. Promising candidates for the production of biologically active agents for food and beverages. The effect on breads are manifold and highly depend on dominant microflora. It has effects on texture, nutrients, flavour and shelf life of the bread.

For the experiments in work package 3 yeasts from the species Saccharomyces cerevisiae have been used. All yeast strains came from different applications such as bread, ale (2x) beer, lager beer, wheat beer and white wine. The sourdoughs are mainly commercial available by Böcker. Böcker sourdoughs are based on different substrate (Wheat malt, wheat milling, wheat starch, mixtures) with different sensory characteristics (mild, acidic, aromatic) and its application form varies between liquid and powder. Above that Elke and her team have identified and isolated two strains with different effects on the bread products.

The results of the work package has shown that it is possible to produce higher quality bread by using yeast coming from the brewing industry, instead of bread containing standard baker's yeast. Yeast strains provide a significant impact on quality parameters of dough and bread and they can be used as a tool to modulate bread characteristics. It is possible to formulate a tailored yeast starter culture, merging the different yeast strains in a specific ratio to optimise the quality of the final bread. The commercial freeze dried and liquid sourdoughs showed no big differences to S. cerevisiae bakers yeast, but they improve the flavour of the bread. The use of sourdough could improve the quality of bread using special selected strains like Lactobacillus reuteri or Weissella cibaria due to their unique characteristics. The combination of different yeasts and sourdoughs together could lead to a superior quality of bread.