In the 19th century, for the first time, bread was made only from beer yeast and new dough (no old dough). The first noted or applauded example of this was the sweet-fermented Imperial "Kaiser-Semmel" roll of the Vienna bakery at the "Paris International Exposition of 1867".[2] These sweet-fermented rolls lacked the acid sourness typical of lactobacillus, and were said to be popular and in high demand.
Prior to this time, bakers had been using old-dough leavens, and they had discovered that accelerating the latter refreshments' rest intervals promoted yeast growth in a race against time and what would later be learned were overwhelming lactobacillus numbers. At some point bakers began to add brewer's or beer yeast or barm to the latter refreshments, and liked the results