Yogurt Preparation Lab (adapted) — Lab Questions

Research Question: Choose the most appropriate research question for this lab based on the objective: In this exercise you will make highly edible yogurt, observe the effect of a starter culture on milk, and compare the quality and flavor of yogurts made with different types of milk.

• How does the type of milk influence the flavor and firmness of yogurt produced with a starter culture?

• What is the global market share of yogurt brands?

• How does boiling water temperature affect pasta cooking time?

• What is the effect of sunlight exposure on average plant height?

Day 1 Step 1 instructs the group to select two types of milk and measure at the milk station. What important behavior is emphasized during measuring and transport to the work area?

• Do not spill milk or create a mess

• Keep the milk uncovered at all times

• Add starter culture before measuring

• Heat the milk while measuring

Day 1 Step 2 states: Transfer the 1 cup of milk to the Pyrex container sitting on the hot plate. What should be the state of the hot plate during this transfer?

• Off

• Low heat

• Medium heat

• High heat

Day 1 Step 3 directs you to heat the milk over medium heat while stirring. To what temperature range should the milk be heated during this step?

• 180–195 °F (82–90 °C)

• 120–135 °F (49–57 °C)

• 210–220 °F (99–104 °C)

• 95–105 °F (35–41 °C)

After heating, the milk should be allowed to cool. To what temperature range should it cool before proceeding?

• 110–115 °F (43–46 °C)

• 140–150 °F (60–66 °C)

• 80–90 °F (27–32 °C)

• 65–75 °F (18–24 °C)

According to the tip, what is a stated purpose of scalding the milk in this procedure?

• To kill remaining milk bacteria after pasteurization and ensure a more consistent product

• To add live bacteria to improve fermentation

• To reduce the fat content of the milk

• To caramelize sugars for sweetness

What additional benefit of scalding is described in the tip regarding milk proteins?

• It helps with “conditioning” or denaturing the milk protein casein, resulting in a smoother yogurt

• It concentrates whey proteins to make the yogurt sour

• It increases the lactose content for faster fermentation

• It prevents evaporation by forming a protective layer

According to the tip, whisking the milk occasionally during heating and cooling primarily helps to:

• Prevent formation of a skin on the milk

• Speed up the boiling process

• Add air to make the yogurt fluffy

• Reduce the temperature more quickly

Which caution is emphasized for the heating step in this procedure?

• Do not allow the milk to boil over

• Always cover the pot while heating

• Add starter culture during the boil

• Do not use a food thermometer

During early incubation, what is the effect of disturbing the yogurt?

• It will interfere with proper setting.

• It accelerates fermentation for faster completion.

• It prevents lactose reduction.

• It eliminates whey separation.