- In this experiment you will make cheese by the same method used for centuries. First, the protein in milk is made solid, and then it is separated from the liquid part of milk. The solid part is called curd, and the liquid is called whey. An enzyme is needed to produce the curd. This enzyme is called rennin and was originally found in the fourth stomach of suckling calves. It is now made in laboratories.
MATERIALS:
Prepared milk, 3/4 cup (3/4 cup of whole milk plus 1 Tbsp of buttermilk)
Burner
Rennin (junket or Rennilase)
Stirrer
Pan
Beaker or glass
Filter paper (or coffee filter)
Thermometer
FunnelPROCEDURE:
REMEMBER: You are going to eat this, so don't do it in the lab.
1. Place the prepared milk in a pan and allow it to sit for 4 hours.
2. Warm the milk to 80-90 deg. F. Be careful not to overheat.
3. While stirring, add one-half of a rennet tablet to the milk. Break the curd that forms into tiny bits.
4. Increase the temperature to 100 deg. F, but no higher.
5. Remove the container from the heat, Pour the curds and whey into the beaker or glass, and allow it to remain undisturbed for 15 min. Observe what happens.
6. Use a funnel with a coffee filter to filter the contents of the beaker. Your cheese is on the filter.
7. Press all of the liquid from the cheese and allow it to dry.
REACTION:
1.Souring of milk: The milk sugar called lactose is changed to milk acid called lactic acid by the action of special bacteria. Lactic acid is a week acid like the acids found in living tissue.
2. Curdling: Curdling occurs when the enzyme, rennin, is added to milk. The insoluble protein, casein, is formed by this reaction.
3. Aging: Cheese develops flavor during this chemical process as the cheese is stored.
QUESTIONS:
1. What is in sour milk that makes it sour instead of sweet?
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2. Why must the temperature be controlled so carefully?
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3. How does your cheese differ from commercially prepared cheese in appearance and taste?
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