A comment on this blog reads as follows:
Your information is INCORRECT. Following is an excerpt from a letter from KRAFT food.
"Thank you very much for asking if Kraft cheese products contain any animal derivatives. Our comments here apply only to products produced in the United States. Many cheese products produced in the United States do contain a coagulating enzyme derived from either beef or swine. The process of changing fluid milk into cheese consists of coagulating the milk by one of two commonly used methods, each resulting in cheese having distinct characteristics.
The most common method of coagulating milk is by the use of an enzyme preparation, rennet, which traditionally was made from the stomachs of veal calves. Since the consumption of calves for veal has not kept pace with the demand for rennet in the preparation of cheese, a distinct shortage of this enzyme has developed. Consequently, a few years ago it became a common practice to mix the rennet extract from calves' stomachs with a pepsin enzyme derived primarily from the stomachs of swine. These enzymes convert the fluid milk into a semi-solid mass as one of the steps in the manufacture of cheese. This mixture of calf rennet and pepsin extract is quite commonly and widely used within the United States."
The pdf file from FAO also mentions the usage of pepsin for cheese making:
Enzyme preparation Used in the preparation of fish meal and other protein hydrolysates, and the clotting of milk in cheese making in combination with one of the rennet.
The Halal Research Council also states that pepsin is generally used for making cheese:
Three enzymes used to make cheese are pepsin, lipase and rennet. These enzymes can be from animal, vegetable or microbial sources. Animal sources include pigs and cattle. Pepsin is derived from pigs, and is Haram.
Almost any source on cheesemaking that can be found online mentions rennet. Pig-based pepsin is not mentioned with the same frequency. This is why I am not sure about the reliability of my sources' claims.
Considering this, is it common practice to use pig based pepsin to make cheese?
I know that whey is also generated in the process of making cheese. Whey powder is a common ingredient in many chocolates. Is it likely that the whey powder in these chocolates was produced with the aid of pig-based pepsin?