The investigation of technological, nutritional and sensorial characteristics of wheat bread, influenced by different strains of Saccharomyces cerevisiae

Yeast induced fermentation of dough is an important process in bread making and one of the oldest biochemical processes in the world. Surprisingly, our knowledge about the dough fermentation step in correlation to product quality parameters is scarce. A literature review revealed that yeast fermentation can be used to improve technological, nutritional and sensorial quality characteristics of breads. This thesis investigates the suitability of various Saccharomyces cerevisiae strains originating from the beverage industry in dough leavening to enhance bread quality characteristics compared to commercial Baker’s yeast. The results revealed that various yeast strains showed large differences in technological bread quality parameters. In the case of bread, starch being the main carbohydrate source, glycaemic control is of great interest. Therefore, the in vitro starch digestibility was analysed in comparison to Baker’s yeast bread (100) for the predicted glycaemic index (pGI). pGI values were significantly lower for S. cerevisiae s-23 (71.6), wb-06 (63.0) and Blanc (77.9). Furthermore, the impact of yeast strains on sensory characteristics, flavour and aroma profile was investigated by gas chromatography mass spectrometry after thermal desorption (GC-MS TD) and descriptive sensory analysis. Due to their specific metabolite production, another important aspect was to adapt the process parameters (fermentation time and temperature). For that reason, response surface methodology (RSM) was used as a model design. A change in fermentation parameters showed further improvement of the breads mainly in terms of prolonged shelf life, lowered pGI and higher consumer acceptance. The increasing fundamental knowledge about dough fermentation generates new opportunities for their use in the baking industry. Furthermore yeast can be used to replace or reduce the amount of expensive additives and dough improvers. This study also opens alternatives to better satisfy the high demand of consumers for an increasing variety of bread products by only changing the yeast culture