Laboratory Activity 3: Teacher Notes
Continued
Answers to Implications and Applications
- 3.3 g (protein)/7.8 g (total protein + carbohydrate) = 42% protein. Powdered milk qualifies as a high protein supplement due to the large amount of protein per unit mass.
- Milk proteins curdle in acid. Orange juice is acidic and can curdle (aggregate) protein.
- Casein (protein) and lactose (carbohydrate).
- The percent composition of fat in the milk.
Post-Laboratory Discussion
Look at the different types of milk and show the different contents. Some examples are 2%, skim, evaporated, powdered, baby formula, goat milk, and deer milk. Discuss the advantages and disadvantages of each type of milk.
Extensions
- Extend this concept to the energy and nutritional value of milk. Calculate the calories in milk using the results of the activity (protein or carbohydrate = 4cal/g; fat = 9 cal/g). Look at the minerals and vitamins in milk and check if they have been added as part of teh fortification of milk.
- Bromine is decolorized by unsaturated fats. Have students do library research on the degree of unsaturation of fats in milk and report on it in the context of other fatty foods.
Assessing Laboratory Learning
- Ask students to explain why the mineral and vitamin content is considered insignificant in the determination of milk composition.
- Ask students to list several common substances that they would expect to coagulate milk, and to explain why.
- Ask students why we extracted and weighed the aqueous layer if they were determining fat content, which was contained in the fat-soluble layer.
