Charming Chemistry Creations: Sourdough Starter

The starter was made a week prior to class by adding all-purpose flour, yeast, and water together in a loosely covered bowl. The bowl was not sealed because bacteria from the air gives sourdough its distinct taste, varying from location to location. After three days, a yellow liquid formed on top of the starter and a fermenting smell persisted. By the time we got to class, the starter had died and the CO2 was gone, eliminating any presence of bubbles. Yeast is a living bacteria and needs a constant supply of food. Flour is it food, but over time, food runs out and the yeast dies. The starter also needs to be constantly stirred to expose the yeast to a food supply. The starter does not become infested with mold over time, because the produced lactic acid kills any present bacteria. Sourdough needs to be constant feed with flour and water and mixed to incorporate more air bubbles into the mixture. To fix our starter, we made a new starter by adding yeast to warm water and letting the starter sit for twenty minutes. The new yeast was added to the old starter to jump start the old starter. We expected the brownies to be more dense since they were sourdough brownies, but they were light and fluffy (McGee, 544).