An industrial food scientist designed a process for the large-scale production of yogurt using a continuous-flow bioreactor. The protocol is summarised below:
Name a genus of bacterium typically present in the starter culture used for yogurt production.
Explain why the milk is heated to 90 ∘C90\text{ }^\circ\text{C}90 ∘C for 15 minutes at the start of the process.
Explain why the milk must be cooled to 43 ∘C43\text{ }^\circ\text{C}43 ∘C before inoculating it with the starter culture.
Explain why the mixture is incubated at 43 ∘C43\text{ }^\circ\text{C}43 ∘C for 6 hours.
During the 6-hour incubation, the pH of the mixture drops from approximately 6.5 to below 4.5. Describe and explain how this drop in pH helps to preserve the yogurt.
