Laboratory Activity 3: Student Version

Continued

  1. Compare your milk analysis with actual amounts listed on a carton of milk.
    1. Can you account for any difference between your results and the listed values?
    2. Why do you think that these average values do not total 100%?
    3. Explain why your laboratory values total 100%
  2. In Part 1, Step 3, why did you use a nonpolar solvent to extract milk fat?
  3. In Part 1, Step 4, what effect would trapping of nonfat milk content in the fat-soluble layer have on you results?
  4. In Part 1, Step 7, what effect would extracting some of the top layer along with the bottom layer have on your results?
  5. In Part 2, Step 1, why does vinegar coagulate the protein?
  6. In Part 4, Step 1, why did you weigh the stirring rod along with the evaporating dish?
  7. In Part 4, Step 4, why did you heat the milk over water? What effect would losing some of the milk solid have on your results?

Implications and Applications

  1. Powdered milk is primarily composed of the milk proteins and carbohydrates. Calculate the percent composition of powdered milk from the previous data. Would powdered milk be a good high protein supplement to add to other foods?
  2. Have you ever accidentally poured orange juice into milk at breakfast? What happened? Why?
  3. In the introduction, milk was discussed as a complete food. Can you name the principle proteins and carbohydrates in milk?
  4. We have studied whole milk. There are other types of milk like 2% milk, 1% milk and skim milk. What do these names imply about the milk composition?

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