1. CURDS AND WHEY
Little Miss Muffet sat on a tuffet Eating her curds and whey, Along came a spider, Who sat down beside her And frightened Miss Muffet away
Rennet is found in the stomachs of calves. It contains enzymes which break
down the protein in milk to make it digestible. Calf rennet contains chymosin
an enzyme which is most important in cheese making. The enzyme coagulates
the milk separating it into curds and whey.
Some people find it unacceptable to eat a product which has been made from
animals. Many years ago this led to the hunt for an alternative milk clotting
product. Some fungi were found which produced enzymes which clotted milk
proteins. These fungi can be grown in fementers and large amounts of the
enzyme can be extracted.
In more recent years the genes, which the calves contain, to allow them to
make chymosin have been identified. These gene have been put into yeast
cells and the yeast cells then produce GM chymosin identical to the animal
enzyme.

2. WHICH RENNET?
You are going to be divided into groups, each group will have about 4 people.
Each group will find out about the different types of rennet and then make a decision about which one they would choose. You can complete the ‘pros’ and ‘cons’ sheet as part of your discussion.
Then you will explain your decision to the class.

3. pros
cons
Calf rennet
GM rennet
(maxiren)
Fungal rennet
(fromase)

4. GM Rennet - Maxiren Background
Rennet is found in the stomachs of calves. It contains enzymes which break down the protein in milk to make it digestible to the animal. Calf rennet contains the enzyme rennin (scientifically known as chymosin ). The gene, which the calves contain, to allow them to make chymosin has been identified. This gene has been put into yeast cells and the yeast cells then produce pure chymosin identical to the animal enzyme.
Scientist How Chymosin is made by yeast
 1. The chymosin making cells are identified from a calf.
 2. The DNA from the cells is isolated and the chymosin gene is cut out using special enzymes.
 3. The chymosin gene is placed into a small loop of DNA (called a plasmid)
 4. The plasmid is put inside a yeast cell
 5. The yeast cells are grown in a fermenter and divide into many millions of cells
6. Chymosin is extracted from the yeast cells
Salesperson - This company is now producing pure chymosin in an exciting new way. We call our product MAXIREN.
Here are some of the advantages which our product has:-
There is no need to slaughter animals.
Maxiren is pure chymosin and not a mixture of enzymes.
The vegetarian society has given their approval to products made from maxiren.
Expert tasters from all over the world cannot detect any difference between cheese made using maxiren and cheese made from calves rennet.
Consumer
I don't want to be responsible for calves being killed to produce rennet. Cheese is a very important part of my diet and I want it to taste good. Maxiren has been produced in a way that does not harm animals and yet it produces cheese which tastes just as good as cheese made from calves rennet. Maxiren uses clever modern technology in its production and I want to support the new ways of doing things. Remember the mad cow disease scare? - I'd rather eat a product which had not been produced from animals

5. Calf Rennet Background
Rennet is found in the stomachs of calves. It contains enzymes which break down the protein in milk to make it digestible to the animal. Calf rennet contains 2 enzymes rennin (chymosin) and
pepsin. Chymosin is the enzyme which is most important in cheese making. The enzyme coagulates the milk separating it into curds and whey. The lining of calves stomachs is processed
to produce this product.
Scientist
Rennet is obtained from the abomasum (fourth stomach) of newly born calves. The rennet is usually obtained from calves which are
being used for veal production. Adult cattle do not contain sufficient quantities of the rennet. The chymosin is extracted by washing and drying the stomach lining. The lining is then cut into small pieces and macerated in a solution of boric acid or brine at 30°C for 4-5 days. Since 1837 calf rennet has been extracted in this way and sold to
the cheese making Industry.
Salesperson -Here are some of the advantages which our product has:-
-Calf rennet was the first ever product which allowed cheese to be made.
-Cheese manufacturers are used to it and are happy with the type of cheese which it makes.
-No genetic engineering has been used to produce calf rennet.
-It is the natural enzyme doing the same job in the calves stomach as it does in the cheese factory.
Consumer- I object to all of the new strange products which have come onto the market. I want to eat good old fashioned cheese which is made the good old fashioned way. The calves are going to be killed anyway so I think that it is good to use the stomachs rather than letting them go to waste. I think that we should support the British farmers and the British farm products such as calf rennet. Lots of people do not want vegetarian products. Human beings evolved to eat meat and most of us want to stay that way.

6. Fungal Rennet - Fromase
Background
Rennet is found in the stomachs of calves. It contains enzymes which break down the protein in milk to make it digestible to the animal. Many people find it unacceptable to eat a product which has been made from animals. Many years ago this led to the hunt for an alternative milk clotting product. Some fungi were found which produced enzymes which clotted milk proteins. These fungi can be grown in fomenters and large amounts of the enzyme can be extracted.
Scientist
The fungus known as Mucor miehei produces a protease enzyme which has high milk clotting activity. The fungi are grown in fermenters at 40°C using potato starch and barley for food. The process takes 5-6 days.
Fromase is more tolerant to high temperatures than other forms of rennet. This is important when producing pasteurized cheese.
Salesperson -Here are some of the advantages which our product has:-
-This was the first ever product which allowed true vegetarian cheese to be made.
-Fungal fromase is much cheaper than any other rennet product.
-There is no need to slaughter animals.
-The vegetarian society has given its approval to products made from fromase.
-No genetic engineering has been used to produce fromlase.
-It is a natural enzyme found in the wild.
Consumer
Vegetarian Cheese has been made for many years with fromase so I trust this type of production. Natural is best. I don't want to eat cheese which has been made from an enzyme which comes from genetically engineered cells.
I don't want to be responsible for calves being killed to produce rennet. I remember mad cow disease and I'd rather eat a product which had not been produced from animals.