Reference no: EM132395695
DIRECTIONS
Lab 8 - Food Chemistry & Digestion:
Read the background information about separating milk in the first page and a half of the lab handout. Then, perform the actual lab activity to separate milk yourself. Take a picture of your experiment and your results to submit. Next, follow the link to the virtual lab for testing for the presence of macromolecules in food. Follow the steps in the lab handout and run the different tests and analyze the hypothetical test results from your separated milk.
Lab Activity: Separate Skim Milk and Whole Milk into Curds and Whey
Materials:
Whole Milk 2 Saucepans or Crockpots
Skim Milk Vinegar or Lemon Juice
Candy thermometer (only if you have already have one) 4 Cups or mugs
Coffee Filters or Paper Towels or Nylon hosiery or Cheesecloth Liquid measuring cup & spoons
Method:
1. Warm the whole milk and skim milk separately in saucepans or crockpots. You only need to heat it to between 85 to 105 degrees Farenheit (29-41 degrees Celcius), so DON'T BOIL THE MILK! If you have a candy thermometer, you can get an exact temperature. Otherwise, this is around body temperature, so if you stick your finger in the milk, it won't feel warm OR cold.
2. Transfer identical volumes of the warm skim and whole milk (such as 1 cup each) to 2 cups or mugs.
3. Add 2 Tablespoons of vinegar or lemon juice to each of your cups of milk.
4. Wait about 10 minutes. By now, you should see the milk completely separating into fluffy white curds and pale yellowish-green whey. If you don't see this, add another Tablespoon of vinegar until you see this.
5. Put a paper towel folded into a funnel shape, a coffee filter, a cheesecloth, or an old pair of nylon hosiery over 2 other cups or mugs. This will filter the curds out and allow the whey to soak through. Do this separately for the skim and whole milk. Remove as much of the whey from the curds as you can.
6. Compare the size of the curd from the whole versus the skim milk (and any other differences you notice). Take a picture of your experiment set up and the curds you produced and submit it with your answers to the questions.
Answer these questions:
1. What does Iodine test for and what color indicates the strongest positive test?
2. What does the Biuret reagent test for and what color indicates the strongest positive test?
3. What does the Benedict reagent test for and what color indicates the strongest positive test?
4. What does the Sudan III stain test for and what color indicates the strongest positive test?
5. What would be a good negative control for all of these tests (same for all tests)?
6. What would be a good positive control food for each of these tests (different for each test)?
7. Why do we use a negative control?
8. Why do we use a positive control?
Circle the correct answer/answers or leave blank if no correct answers:
9. Is there sugar in whole milk? yes no
10. When you separate milk into whey and curds, where is the sugar? whey curds
11. Is there starch in whole milk? yes no
12. When you separate milk into whey and curds, where is the starch? whey curds
13. Are there lipids in whole milk? yes no
14. When you separate milk into whey and curds, where are the lipids? whey curds
15. Is there protein in whole milk? yes no
16. When you separate milk into whey and curds, where is the protein? whey curds
17. Which contains more protein? whey curds
18. Which of the 4 macromolecules are found in whole milk?
19. Which of the 4 macromolecules are found in cheese?
20. Traditionally, whey was considered a waste product of cheese production, although farmers would often feed it to their pigs. Search the internet and list a few ways whey is used now so that it isn't wasted.
21. Animal rennet works best from 85 - 105 degrees Farenheit (29 - 41 degrees Celcius) and also works best in an acid (low pH) environment. Why? (Think about where it comes from).
22. Why do we get animal rennet from calf stomachs? (What is it about them that causes it to work?)
23. Did you produce more curds from skim or whole milk? What caused the difference in curd yields?
24. Were there any other differences in the curds produced from skim versus whole milk?
Attachment:- Separate Skim Milk.rar