Cheese Making

Introduction:

In this activity you will be fermenting milk products. The action of bacteria in milk causes a buildup of lactic acid. This lactic acid causes the milk to curdle, forming a solid curd, and a liquid whey. The curd is then separated from the whey and aged to make cheese. The physical characteristics of the cheese depend on many factors. Below is a basic "recipe" for making cheese. You will be responsible for making a control sample following this formula and at least one other batch of cheese in which you have changed one factor. You need to hypothesize what differences your experimental group(s) will have as compared to your control. Be sure to follow aseptic technique and use only food-grade containers for this experiment. You must submit a proposal on what your experimental group(s) will entail before beginning this laboratory work.

Materials:

500 mL whole milk
hot plate
fine-mesh cheesecloth
labels
50 mL, 500 mL and 600 mL containers
50 mL buttermilk
thermometer
cotton twine
50 mL, 500 mL and 600 mL measuring devices

Cautions:

  1. Wash hands thoroughly with antibacterial soap and water before and after completing each step of the laboratory.
  2. Be aware of shock and burn hazards when using the hot plate
  3. Wear goggles and laboratory apron

Procedure:

Day 1

  1. Make sure all materials, equipment and your hands are as clean as possible. Wash hands before handling any materials.
  2. Pour 500 mL whole milk into your 600 mL container and 50 mL buttermilk into your 50 mL container.
  3. Heat the whole milk to 37 degrees C.
  4. Add the buttermilk to the whole milk and stir well.
  5. Cover the container with cloth or paper.
  6. Incubate at between 25 and 35 degrees C for 48 hours or until a firm curd has separated from the whey.

Day 2

  1. Prepare a piece of cheesecloth that will be thick enough and large enough to hold your curd.
  2. Pour your curd into the cloth. Collect the whey in the 500 mL container. Gather the edges of the cloth to form a bag. Tie the bag with the twine and hang it to continue draining. After it has fully drained, discard the whey and place the bag in the refrigerator.

Day 3

No work necessary today.

Day 4

Remove the cheese and enjoy!

Reference:

Pam DiFilippo, San Juan High School, Citrus Heights, CA, ""Making Cheese," Biotechnology Manual, Addison Wesley.

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