Question

Madison is conducting a biotechnology experiment in her kitchen. Her goal is to make yogurt with a pH of 4.5 in the optimal time of 4 hours. Normally, she uses a mixed culture of L. bulgaricus and S. thermophiles to ferment yogurt. She designs her experiment to include the mixed cultures but also with the L. bulgaricus culture alone to see if one would ferment faster. She graphs her results to display her data.The graph depicts the results of an experiment to make yogurt. Over six hours, milk maintains 6.5 pH. When L. bulgaricus is added to milk, the pH declines from 6.5 to about 4.3 in six hours. When L. bulgaricus and S. thermophilis are added, the pH declines over six hours to approximately 3.5.Study the graph of her results.Certain bacteria that produce lactic acid as a waste product during fermentation, an Choose... process, are important to the food industry. This lactic acid is what gives yogurt its Choose... taste. From the graph, based on the pH after 4 hours, the Choose... would taste the most acidic.

Answer 1

Firstly, Milk alone did not ferment or change in pH at all, showing that it is a control variable on this experiment. The L. bulgaricus culture alone did not meet Madison's goal to make yogurt with a pH of 4.5 within 4 hours; however, the mixed culture S. thermophilis and L. bulgaricus met Madison's goal of reaching a 4.5 pH. In conclusion, the mixed culture is the fastest fermenting culture that madison has, and it meets her goal of reaching a pH of 4.5 in the optimal time of 4 hours.