How is cheese made, and why does it need a Hachsher if all milk is Kosher?
• ANSWER: The laws of Kosher as they pertain to cheeses are complex and prevent many mass producing cheese companies from becoming kosher. Below we’ve included a discussion of the issues involved in making cheese kosher. The discussion pertains to ‘hard’ cheese (which we are assuming you are asking about) and not about soft, spreadable or acid set cheeses such as cottage, cream and farmers cheese. Rennet How does one make cheese? Hard cheese is made by souring (fermenting) the milk to impart the desired flavor then curdling the casein fraction of the milk. Historically, milk was curdled by using an enzyme called rennin, an enzyme which affects protein (called protease) and is derived from an extract of the stomach of a suckling calf. This extract is known today as rennet. In response to the obvious question, the Shach (Rabbi Shabsi Kohen, a great Talmudic and Halachic Scholar) in Yoreh Deiah 87: No 35 raised the question of why the use of such rennet would violate the prohibition of mi
