Microbes in Milk

The video tutorial explores bacterial growth in different types of milk: pasteurized, UHT, and powdered. Using a rezazurin indicator, the experiment measures bacterial activity by observing color changes in milk samples left unrefrigerated for three days. Pasteurized milk shows the most bacterial activity, UHT milk shows moderate activity, and powdered milk shows little to none. The experiment highlights how milk treatment affects bacterial growth, with implications for other pasteurized, UHT, and powdered products.

What is the purpose of using rezazurin indicator in the milk experiment?

• To preserve the milk for a longer time

• To change the flavor of the milk

• To indicate the level of bacterial activity

• To measure the temperature of the milk

Why are the milk samples incubated at 37°C during the experiment?

• To freeze the milk

• To provide optimal conditions for bacterial respiration

• To evaporate the milk

• To sterilize the milk completely

Which type of milk showed the greatest change in color, indicating the highest bacterial activity?

• UHT milk

• Powdered milk

• Fresh pasteurized milk

• Condensed milk

What does a blue to pink color change in UHT milk indicate?

• The milk has no bacterial activity

• The milk is fresh

• The milk is close to spoiling

• The milk is completely spoiled

Why does powdered milk show little to no color change in the experiment?

• It contains preservatives

• It is kept at a low temperature

• It is stored in a sealed container

• Bacteria cannot survive without moisture

What is the main advantage of UHT processing in food preservation?

• It reduces the cost of production

• It removes all bacteria, extending shelf life

• It enhances the flavor of the food

• It makes the food more nutritious

Who invented the process of pasteurization?

• Louis Pasteur

• Alexander Fleming

• Marie Curie

• Isaac Newton