NAME:______DATE:______PERIOD:______
Enzymes and Cheese-making
Much of our food consists of proteins. Proteins are large molecules of amino acids linked together. Rennilase is an enzyme which breaks down protein into smaller amino acids. Rennilase is naturally present in the stomach lining of living things. When rennilase breaks down protein from milk, it causes the milk to coagulate or clot. The clotted protein is cheese.
Cheese-making was probably discovered by accident over a thousand years ago. Primitive humans were hunters and gatherers, using every source of food they encountered. They stored water in the stomachs of the animals they slaughtered for food. Someone stored milk in a portable animal stomach, only to find that after time, the milk had turned into soft, creamy edible cheese. Primitive humans did not understand why this had occurred, but they began to intentionally make and eat cheese.
Today, cheese is made with milk from cows, goats, sheep, buffalo, and reindeer. Microorganisms are used for their rennilase instead of the use of a stomach. The use of different microorganisms and techniques can produce cheese with different textures, flavors and odors. There are over 400 varieties of cheese. The average American eats about nine pounds of cheese a year!
Today you will make cottage cheese using rennilase and whole milk. You will separate the hard part of the cheese (the curd) from the liquid part (the whey). The curds will ripen overnight in the refrigerator.
If you are lactose intolerant, please do not taste the cheese.
Procedure:
1.WASH YOUR HANDS BEFORE YOU BEGIN!
2.Your group will receive 2/3 of a cup of heated whole milk. The milk has been heated to 90C.
3.Allow milk to cool for 2-3 minutes.
4.Your teacher will add 3-5 drops of rennilase and stir.
5.Allow the cup to sit undisturbed for at least 20 minutes. While you are waiting, please answer the questions. You will notice the milk is now liquid (whey) and solid (curds).
6.Take one square of cheesecloth and place it over the top of the empty cup. Place a rubberband tightly around the cup and cheesecloth.
7.While holding the cheesecloth tightly over the top of the cup, pour the contents of the cup over the cheesecloth. They whey will drain in to the cup. The curds will remain on top of the cheesecloth.
8.Gently squeeze the curds in the cheesecloth until most of the whey has drained into the cup.
9.Wrap the cheesecloth and curds in saran wrap and label it with your names.
Questions:
1. What group of macromolecules does cheese fit into?
2. What group of macromolecules does rennilase fit into?
3. What do enzymes do?
4. How are enzymes involved in cheese-making?
5. Where is rennilase found in living things?
6.Do we usually eat the curds or the whey?
7. What type of cheese did we make?
8.Research your favorite kind of cheese. Describe how it is made (no less than 5 sentences)
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